Date   

Re: Intermitten tx

Robert Blackburn
 

As long as the 7000 had been around everyone needs to know that the original fuses and fuse holders are notorious for causing transmit problems.


On Jul 27, 2021, at 18:59, Michael Forsythe <mike@...> wrote:

OK... some progress....

after opening up and looking for voltage drop in tx it turns out i had a bad fuse holder in the power cable.... and although the same mic can key my icom vhf into TX over and over, it does not work on the IC7000. i crimped some wire into a RJ45 and touched TX to ground and it works every time, seems issues were external to radio. 


Re: Intermitten tx

Michael Forsythe
 

OK... some progress....

after opening up and looking for voltage drop in tx it turns out i had a bad fuse holder in the power cable.... and although the same mic can key my icom vhf into TX over and over, it does not work on the IC7000. i crimped some wire into a RJ45 and touched TX to ground and it works every time, seems issues were external to radio. 


Re: Help me fix my latest IC7000 failure

Kurt Sweeny
 

Bob,

 

‘ Interesting context and background. ‘Good thing this was just a one off type of regulatory problem.

 

Thanks,

 

Kurt

KD6LZV

 

 

From: ic7000@groups.io <ic7000@groups.io> On Behalf Of montanaaardvark
Sent: Tuesday, July 27, 2021 11:29 AM
To: ic7000@groups.io
Subject: Re: [ic7000] Help me fix my latest IC7000 failure

 


I'd go with the first one.  I've heard of it, but I don't remember seeing one.  It may be that I saw one and forgot about it, although we tend to remember the weird things and not the everyday.

It's possible for chip resistors to be manufactured shorted, but I don't know how they grow shorts and go bad.  It may be that the circuit board can grow shorts because certain solders can grow whiskers or dendrites that short out parts. That depends on time, temperature, humidity, and the type of solder.  That was more common in the early days of lead-free solders, which was around '06 to '08 (very approximately).  Coincidentally that's around the time the 7000 was in production.  

Because we refer to parts being solder coated as being "tinned" it's ironic that the worst solders for growing whiskers were bright tin solders.  Matte tin solder was better, but still not as good as tin-lead. 

I think the European Union was first to introduce laws against tin-lead solders.  The impact on reliability was anticipated; they knew consumer items would fail earlier, but they made specific exceptions for high-reliability stuff like military, space, and civil aviation (where I worked).  The problem was that the people who make components don't want to retool their line for different manufacturing lots of parts for the small market instead of just making different values for everyone, so the high-rel companies had to figure out how to solder the lead free parts onto circuit boards and ensure the leads were covered with solder. 

Being typical regulators, they went after the molehill and not the mountain; the tiny amount of lead used in solder vs. the lead used in batteries.  The total world use of lead is about 90 percent for batteries, and the amount used in electronics (excluding batteries) is all of 2 percent. Further, of the lead in landfills (supposedly what they're trying to reduce), the overwhelming majority is coming from the disposal of TV CRTs and monitors, which can contain up to 2 kg of lead per tube, not from circuit board assemblies, by a massive ratio of 9 to 1.

To reduce the amount of lead in landfills, they went after the tiny amount of lead in solder, and increased the amount of junk in total that would go to the landfills because of the lower lifetime.

Some industry chatter that may be informative.
https://www.aviationtoday.com/2012/07/01/system-design-death-by-tin-whiskers/ 
https://nepp.nasa.gov/WHISKER/background/  (I think this one is worth reading)
https://nepp.nasa.gov/whisker/dendrite/index.html


73,
Bob
--
W4ATM - 35 Miles south of the Kennedy Space Center
Retired RF Design Engineer
Now able to play with all the hobbies I never had enough time for


Re: Help me fix my latest IC7000 failure

Dan Smith - KK7DS
 

I'd go with the first one. I've heard of it, but I don't remember seeing one. It may be that I saw one and forgot about it, although we tend to remember the weird things and not the everyday.
Okay, well, I'm definitely going with "it seems fixed now, regardless" :)

It's possible for chip resistors to be manufactured shorted, but I don't know how they grow shorts and go bad. It may be that the circuit board can grow shorts because certain solders can grow whiskers or dendrites that short out parts. That depends on time, temperature, humidity, and the type of solder. That was more common in the early days of lead-free solders, which was around '06 to '08 (very approximately). Coincidentally that's around the time the 7000 was in production.
Thanks for the fascinating summary of the consequences of lead-free solders (a problem I didn't realize existed) and the dangers of over-regulation (a problem I *did* realize existed). Based on that, I suppose maybe just the act of removing it and cleaning the pads was the fix. When I tested it on the bench, I got one reading on it, then went to reposition with the tweezers which is when it left for orbit. I suppose it's possible that I got a bad read on it the first time with my comparatively large meter probes, or that it had become bridged on the backside from the extra solder I added at removal. I feel fairly confident in the testing I did whilst it was secured on the board though.

--Dan


Re: Help me fix my latest IC7000 failure

montanaaardvark
 


I'd go with the first one.  I've heard of it, but I don't remember seeing one.  It may be that I saw one and forgot about it, although we tend to remember the weird things and not the everyday.

It's possible for chip resistors to be manufactured shorted, but I don't know how they grow shorts and go bad.  It may be that the circuit board can grow shorts because certain solders can grow whiskers or dendrites that short out parts. That depends on time, temperature, humidity, and the type of solder.  That was more common in the early days of lead-free solders, which was around '06 to '08 (very approximately).  Coincidentally that's around the time the 7000 was in production.  

Because we refer to parts being solder coated as being "tinned" it's ironic that the worst solders for growing whiskers were bright tin solders.  Matte tin solder was better, but still not as good as tin-lead. 

I think the European Union was first to introduce laws against tin-lead solders.  The impact on reliability was anticipated; they knew consumer items would fail earlier, but they made specific exceptions for high-reliability stuff like military, space, and civil aviation (where I worked).  The problem was that the people who make components don't want to retool their line for different manufacturing lots of parts for the small market instead of just making different values for everyone, so the high-rel companies had to figure out how to solder the lead free parts onto circuit boards and ensure the leads were covered with solder. 

Being typical regulators, they went after the molehill and not the mountain; the tiny amount of lead used in solder vs. the lead used in batteries.  The total world use of lead is about 90 percent for batteries, and the amount used in electronics (excluding batteries) is all of 2 percent. Further, of the lead in landfills (supposedly what they're trying to reduce), the overwhelming majority is coming from the disposal of TV CRTs and monitors, which can contain up to 2 kg of lead per tube, not from circuit board assemblies, by a massive ratio of 9 to 1.

To reduce the amount of lead in landfills, they went after the tiny amount of lead in solder, and increased the amount of junk in total that would go to the landfills because of the lower lifetime.

Some industry chatter that may be informative.
https://www.aviationtoday.com/2012/07/01/system-design-death-by-tin-whiskers/ 
https://nepp.nasa.gov/WHISKER/background/  (I think this one is worth reading)
https://nepp.nasa.gov/whisker/dendrite/index.html


73,
Bob
--
W4ATM - 35 Miles south of the Kennedy Space Center
Retired RF Design Engineer
Now able to play with all the hobbies I never had enough time for


Re: Help me fix my latest IC7000 failure

Dan Smith - KK7DS
 

I've got to tell you, in about 40 years in the electronics manufacturing industry including the last 25 working with chip components, I can't recall seeing a single shorted resistor.

Congrats on finding that!
Wow, this makes me nervous that I'm wrong! I mean, replacing it definitely fixed it, but...

As noted in the post, I measured it in-circuit, then with the ribbon cable disconnected. With the cable disconnected, I got a different measurement to ground than with it connected, so I was quite sure that freed up one end. Once it was out I again measured it as shorted on the bench. Unfortunately, after that I went to pick it up with the tweezers and shot it across the room never to be found again, so I can't go back and re-re-confirm.

Is this like "it happens but it's rare" or "it doesn't/can't happen"?

--Dan


Re: Help me fix my latest IC7000 failure

montanaaardvark
 

On Sun, Jul 25, 2021 at 05:37 PM, Dan Smith - KK7DS wrote:
hope I'm not bothering anyone with this, but I think I've resolved this power meter issue as well. Details here:

http://www.danplanet.com/blog/2021/07/25/resolving-an-icom-ic-7000-power-meter-problem/

tl;dr: another problem resistor, this time shorted, in the ALC circuit.

--Dan
I've got to tell you, in about 40 years in the electronics manufacturing industry including the last 25 working with chip components, I can't recall seeing a single shorted resistor.  

Congrats on finding that!


73,
Bob
--
W4ATM - 35 Miles south of the Kennedy Space Center
Retired RF Design Engineer
Now able to play with all the hobbies I never had enough time for


Re: Help me fix my latest IC7000 failure

Michael Forsythe
 

thanks for all the information. 

On Sun, 25 Jul 2021 at 17:37, Dan Smith - KK7DS via groups.io <dsmith=danplanet.com@groups.io> wrote:
I hope I'm not bothering anyone with this, but I think I've resolved this power meter issue as well. Details here:

http://www.danplanet.com/blog/2021/07/25/resolving-an-icom-ic-7000-power-meter-problem/

tl;dr: another problem resistor, this time shorted, in the ALC circuit.

--Dan

> On Jul 23, 2021, at 13:25, Dan Smith - KK7DS via groups.io <dsmith=danplanet.com@groups.io> wrote:
>
> Unfortunately, the saga continues. Would love some ideas on next steps.
>
> After DigiKey and FedEx conspired against me, I finally received the replacement regulator and resistor that I needed to get the radio back together. I did that, and it happily powers up and seems to behave like normal -- on receive.
>
> Now, when I transmit, I get weird behavior. On SSB with no modulation, power output reads almost half scale. However, on RTTY I get about 80% with RF power set to 100%.
>
> The "power out with no modulation" behavior on SSB makes me think of self-oscillation, but I don't think it explains the RTTY "not full power" behavior. I pulled the covers off and re-sprung the ground springy things, but no difference. I wonder if the microprocessor resistor failure was actually a secondary effect of something in the TX path...
>
> Any ideas?
>
> --Dan
>
>> On Jul 11, 2021, at 9:37 PM, Dan Smith - KK7DS via groups.io <dsmith=danplanet.com@groups.io> wrote:
>>
>> Well, sorry to be that guy that replies to his own emails. Further analysis for the archives:
>>
>> I think I've got it worked out. Initially I was assuming there was something on the logic board that was drawing down the 3.3v line. So, I tried feeding the regulator input directly with the logic board not seated in the main board. That worked fine, with the regulator output at 3.3v and the input holding where I was feeding it. So, I thought maybe it was something on the main board drawing it to ground between the logic board connector and the head connector. There was no path to ground between pin 2 on the head connector that I could measure, so I seated the logic board back in the main board, with the main DC power disconnected and direct-fed the regulator on the logic board again. With that, I got a solid 3.3v at the head connector. However, if I powered the unit through the main DC connector, I'd get the same deal: low regulator HV input line, low regulator output, and low voltage at the head connector.
>>
>> This led to me to think there was a high resistance in the path feeding the HV line. With no load, it would measure 14v, but under load it would draw down. I traced that to the PA board, where the HV line passes through EP703 (RFI choke I think) and R723, which I assume is a current limiting resistor to protect the always-on HV line. Measuring in-circuit, the choke was zero ohms (as expected), and R723 measured 52 ohms. It's marked in the service manual as 4.7. So, I bypassed R723 with a big and ugly 1/4 watt resistor of the lowest value from my stash (10 ohm) and...IT WORKED.
>>
>> I haven't done any more checking on things other than that it now powers up and seems to be okay otherwise, but hopefully that's it. So, I've got to replace the regulator I removed, and get real good at microsurgery real fast so I can replace R723.
>>
>> Longer-term I need to figure out if I want to keep this thing around once I get it patched up. I love it, but it seems like a ticking time bomb.
>>
>> Still happy to hear any commentary on this and the previous analysis. Maybe all the issues I've had have something in common and fixing that would help this thing live a long life?
>>
>> --Dan
>>
>>
>>> On Jul 11, 2021, at 13:46, Dan Smith - KK7DS via groups.io <dsmith=danplanet.com@groups.io> wrote:
>>>
>>> Hi all,
>>>
>>> I'm looking for some help with my IC7000. I apologize for being wordy, it's in my nature and I can't help it. I'll provide a little background, in case it's relevant. If not, just skip to the problem description.
>>>
>>> === Background ===
>>>
>>> I've used it quite a bit off an on over the years, but we have a bit of a dysfunctional relationship. I used to use it for a lot of portable (early days of SOTA) work in all kinds of conditions. It never got really wet or anything, and doesn't show any corrosion anywhere, but it has been outside quite a bit. Many years ago, it started doing this thing where it would just go deaf (all HF bands at least) on and off. Like, it would be sitting there in RX, showing S5 background noise, then ... silent S0 for ten minutes or so, then back to S5 like nothing happened. No touching, no external stimulus. I made a private youtube video showing it happen, wrote up a bunch of diagnosis and details, and sent it to Icom. They called me back, saying that they couldn't reproduce the problem, refused to look at the video, and thus were just sending it back to me with the ribbon cables reseated. I was super frustrated with this response (it was actually worse than I describe), so when I got it back, I literally put it on a shelf. A couple years later, I pulled it out to use it and got just the click-click-of-death thing. Back on the shelf, but later I diagnosed the shorted tantalum cap in the head, replaced, and it would power up. Back on the shelf without much use. Recently got it back out, and spent a day working it pretty hard on several bands and was thrilled to have my old friend back. Until it let me down again. On to the problem description:
>>>
>>> === Problem Description ===
>>>
>>> Yesterday while working it, it started to power off when I would transmit. At one point it got into a really weird reboot loop where the relay that clicks on when you power it up would click on and off, on and off whenever it had external power. Click, click, click .. until I pull the power cable. No head input would stop it. Left it unplugged for a while and then it powered back on normally. Worked it for another hour and then it shut off again during transmit -- for would be the last time. After this, I get no click-click when I hit the power button, no activity at all when it is given power. Just totally dead like a brick. No burning smell either, for what it's worth.
>>>
>>> === Diagnosis ===
>>>
>>> After much pouring over the service manual and tracing things out inside, I arrived at the IC1251 3.3v regulator on the logic unit. This (AFAICT) takes the 14v HV line and regulates it down to 3.3v to power the CPU and is required for the PWRK circuit to initiate the startup. This regulator was showing about 2.7v on the input and 2.4v on the output leg. Confirmed on the head connector pin 2 (with the head detached) that it's sitting at 2.4v instead of what I would expect to be 3.3v. I can probe the HV line on the main board right by the connector that feeds the logic board, and see that it sits at 14v when the logic board is out, and drops to 3.7v or so with the logic board in place. This indicates to me that something on the logic board is pulling that down real far.
>>>
>>> I did what I could to check the bypass caps along the input and output lines to that regulator, but they're, uh, real small and stuff. So, I decided that a sane course of action would be to pop the regulator out so I could isolate before and after it. I got it out clean (although I pulled a leg off it so I'll have to replace that at least). As soon as I did, the HV line went back up to 14v, so I was hopeful that the regulator was bad. However, I wedged a TO-220 3.3v regulator from my parts box into the spot just to test, and it does the same thing. Without the output leg of the regulator connected to the board, it sits at 3.3v and the input sits at 14v. When I connect it to the output pad, it drops down and pulls the input with it, just like the original one.
>>>
>>> As I mentioned, I tried to check what I could that is downstream of that regulator, specifically bypass caps C1252, C1317, C1317 although the latter two are so dang small I have no idea if I'm really on them. But, they don't seem to be shorted, best I can tell. The battery diode D1301 seems fine, and the battery voltage is 3.1v. Other than that, I'm at a bit of a dead end.
>>>
>>> I assume I'm correct that ~2.4v at the head connector and output of the regulator is too low, and that the input shouldn't be pulled down that low, if not for something drawing a lot of current. Is that correct?
>>>
>>> What else could I reasonably do to poke? Wild guesses, as well as informed ones, are welcomed.
>>>
>>> Thanks!
>>>
>>> --Dan
>>>
>>>
>>>
>>
>>
>>
>>
>
>
>
>








--
Mike Forsythe
Managing Director
(242) 359 0797 


Re: Help me fix my latest IC7000 failure

Don Rolph
 

I read your blog posts on this.

Your effort was truly impressive!

My hat is off to you!

I will remember this if my IC7000 acts up.

Thanks!

On Sun, Jul 25, 2021 at 5:37 PM Dan Smith - KK7DS via groups.io <dsmith=danplanet.com@groups.io> wrote:
I hope I'm not bothering anyone with this, but I think I've resolved this power meter issue as well. Details here:

http://www.danplanet.com/blog/2021/07/25/resolving-an-icom-ic-7000-power-meter-problem/

tl;dr: another problem resistor, this time shorted, in the ALC circuit.

--Dan

> On Jul 23, 2021, at 13:25, Dan Smith - KK7DS via groups.io <dsmith=danplanet.com@groups.io> wrote:
>
> Unfortunately, the saga continues. Would love some ideas on next steps.
>
> After DigiKey and FedEx conspired against me, I finally received the replacement regulator and resistor that I needed to get the radio back together. I did that, and it happily powers up and seems to behave like normal -- on receive.
>
> Now, when I transmit, I get weird behavior. On SSB with no modulation, power output reads almost half scale. However, on RTTY I get about 80% with RF power set to 100%.
>
> The "power out with no modulation" behavior on SSB makes me think of self-oscillation, but I don't think it explains the RTTY "not full power" behavior. I pulled the covers off and re-sprung the ground springy things, but no difference. I wonder if the microprocessor resistor failure was actually a secondary effect of something in the TX path...
>
> Any ideas?
>
> --Dan
>
>> On Jul 11, 2021, at 9:37 PM, Dan Smith - KK7DS via groups.io <dsmith=danplanet.com@groups.io> wrote:
>>
>> Well, sorry to be that guy that replies to his own emails. Further analysis for the archives:
>>
>> I think I've got it worked out. Initially I was assuming there was something on the logic board that was drawing down the 3.3v line. So, I tried feeding the regulator input directly with the logic board not seated in the main board. That worked fine, with the regulator output at 3.3v and the input holding where I was feeding it. So, I thought maybe it was something on the main board drawing it to ground between the logic board connector and the head connector. There was no path to ground between pin 2 on the head connector that I could measure, so I seated the logic board back in the main board, with the main DC power disconnected and direct-fed the regulator on the logic board again. With that, I got a solid 3.3v at the head connector. However, if I powered the unit through the main DC connector, I'd get the same deal: low regulator HV input line, low regulator output, and low voltage at the head connector.
>>
>> This led to me to think there was a high resistance in the path feeding the HV line. With no load, it would measure 14v, but under load it would draw down. I traced that to the PA board, where the HV line passes through EP703 (RFI choke I think) and R723, which I assume is a current limiting resistor to protect the always-on HV line. Measuring in-circuit, the choke was zero ohms (as expected), and R723 measured 52 ohms. It's marked in the service manual as 4.7. So, I bypassed R723 with a big and ugly 1/4 watt resistor of the lowest value from my stash (10 ohm) and...IT WORKED.
>>
>> I haven't done any more checking on things other than that it now powers up and seems to be okay otherwise, but hopefully that's it. So, I've got to replace the regulator I removed, and get real good at microsurgery real fast so I can replace R723.
>>
>> Longer-term I need to figure out if I want to keep this thing around once I get it patched up. I love it, but it seems like a ticking time bomb.
>>
>> Still happy to hear any commentary on this and the previous analysis. Maybe all the issues I've had have something in common and fixing that would help this thing live a long life?
>>
>> --Dan
>>
>>
>>> On Jul 11, 2021, at 13:46, Dan Smith - KK7DS via groups.io <dsmith=danplanet.com@groups.io> wrote:
>>>
>>> Hi all,
>>>
>>> I'm looking for some help with my IC7000. I apologize for being wordy, it's in my nature and I can't help it. I'll provide a little background, in case it's relevant. If not, just skip to the problem description.
>>>
>>> === Background ===
>>>
>>> I've used it quite a bit off an on over the years, but we have a bit of a dysfunctional relationship. I used to use it for a lot of portable (early days of SOTA) work in all kinds of conditions. It never got really wet or anything, and doesn't show any corrosion anywhere, but it has been outside quite a bit. Many years ago, it started doing this thing where it would just go deaf (all HF bands at least) on and off. Like, it would be sitting there in RX, showing S5 background noise, then ... silent S0 for ten minutes or so, then back to S5 like nothing happened. No touching, no external stimulus. I made a private youtube video showing it happen, wrote up a bunch of diagnosis and details, and sent it to Icom. They called me back, saying that they couldn't reproduce the problem, refused to look at the video, and thus were just sending it back to me with the ribbon cables reseated. I was super frustrated with this response (it was actually worse than I describe), so when I got it back, I literally put it on a shelf. A couple years later, I pulled it out to use it and got just the click-click-of-death thing. Back on the shelf, but later I diagnosed the shorted tantalum cap in the head, replaced, and it would power up. Back on the shelf without much use. Recently got it back out, and spent a day working it pretty hard on several bands and was thrilled to have my old friend back. Until it let me down again. On to the problem description:
>>>
>>> === Problem Description ===
>>>
>>> Yesterday while working it, it started to power off when I would transmit. At one point it got into a really weird reboot loop where the relay that clicks on when you power it up would click on and off, on and off whenever it had external power. Click, click, click .. until I pull the power cable. No head input would stop it. Left it unplugged for a while and then it powered back on normally. Worked it for another hour and then it shut off again during transmit -- for would be the last time. After this, I get no click-click when I hit the power button, no activity at all when it is given power. Just totally dead like a brick. No burning smell either, for what it's worth.
>>>
>>> === Diagnosis ===
>>>
>>> After much pouring over the service manual and tracing things out inside, I arrived at the IC1251 3.3v regulator on the logic unit. This (AFAICT) takes the 14v HV line and regulates it down to 3.3v to power the CPU and is required for the PWRK circuit to initiate the startup. This regulator was showing about 2.7v on the input and 2.4v on the output leg. Confirmed on the head connector pin 2 (with the head detached) that it's sitting at 2.4v instead of what I would expect to be 3.3v. I can probe the HV line on the main board right by the connector that feeds the logic board, and see that it sits at 14v when the logic board is out, and drops to 3.7v or so with the logic board in place. This indicates to me that something on the logic board is pulling that down real far.
>>>
>>> I did what I could to check the bypass caps along the input and output lines to that regulator, but they're, uh, real small and stuff. So, I decided that a sane course of action would be to pop the regulator out so I could isolate before and after it. I got it out clean (although I pulled a leg off it so I'll have to replace that at least). As soon as I did, the HV line went back up to 14v, so I was hopeful that the regulator was bad. However, I wedged a TO-220 3.3v regulator from my parts box into the spot just to test, and it does the same thing. Without the output leg of the regulator connected to the board, it sits at 3.3v and the input sits at 14v. When I connect it to the output pad, it drops down and pulls the input with it, just like the original one.
>>>
>>> As I mentioned, I tried to check what I could that is downstream of that regulator, specifically bypass caps C1252, C1317, C1317 although the latter two are so dang small I have no idea if I'm really on them. But, they don't seem to be shorted, best I can tell. The battery diode D1301 seems fine, and the battery voltage is 3.1v. Other than that, I'm at a bit of a dead end.
>>>
>>> I assume I'm correct that ~2.4v at the head connector and output of the regulator is too low, and that the input shouldn't be pulled down that low, if not for something drawing a lot of current. Is that correct?
>>>
>>> What else could I reasonably do to poke? Wild guesses, as well as informed ones, are welcomed.
>>>
>>> Thanks!
>>>
>>> --Dan
>>>
>>>
>>>
>>
>>
>>
>>
>
>
>
>








--

73,
AB1PH
Don Rolph


Re: Help me fix my latest IC7000 failure

Dan Smith - KK7DS
 

I hope I'm not bothering anyone with this, but I think I've resolved this power meter issue as well. Details here:

http://www.danplanet.com/blog/2021/07/25/resolving-an-icom-ic-7000-power-meter-problem/

tl;dr: another problem resistor, this time shorted, in the ALC circuit.

--Dan

On Jul 23, 2021, at 13:25, Dan Smith - KK7DS via groups.io <dsmith=danplanet.com@groups.io> wrote:

Unfortunately, the saga continues. Would love some ideas on next steps.

After DigiKey and FedEx conspired against me, I finally received the replacement regulator and resistor that I needed to get the radio back together. I did that, and it happily powers up and seems to behave like normal -- on receive.

Now, when I transmit, I get weird behavior. On SSB with no modulation, power output reads almost half scale. However, on RTTY I get about 80% with RF power set to 100%.

The "power out with no modulation" behavior on SSB makes me think of self-oscillation, but I don't think it explains the RTTY "not full power" behavior. I pulled the covers off and re-sprung the ground springy things, but no difference. I wonder if the microprocessor resistor failure was actually a secondary effect of something in the TX path...

Any ideas?

--Dan

On Jul 11, 2021, at 9:37 PM, Dan Smith - KK7DS via groups.io <dsmith=danplanet.com@groups.io> wrote:

Well, sorry to be that guy that replies to his own emails. Further analysis for the archives:

I think I've got it worked out. Initially I was assuming there was something on the logic board that was drawing down the 3.3v line. So, I tried feeding the regulator input directly with the logic board not seated in the main board. That worked fine, with the regulator output at 3.3v and the input holding where I was feeding it. So, I thought maybe it was something on the main board drawing it to ground between the logic board connector and the head connector. There was no path to ground between pin 2 on the head connector that I could measure, so I seated the logic board back in the main board, with the main DC power disconnected and direct-fed the regulator on the logic board again. With that, I got a solid 3.3v at the head connector. However, if I powered the unit through the main DC connector, I'd get the same deal: low regulator HV input line, low regulator output, and low voltage at the head connector.

This led to me to think there was a high resistance in the path feeding the HV line. With no load, it would measure 14v, but under load it would draw down. I traced that to the PA board, where the HV line passes through EP703 (RFI choke I think) and R723, which I assume is a current limiting resistor to protect the always-on HV line. Measuring in-circuit, the choke was zero ohms (as expected), and R723 measured 52 ohms. It's marked in the service manual as 4.7. So, I bypassed R723 with a big and ugly 1/4 watt resistor of the lowest value from my stash (10 ohm) and...IT WORKED.

I haven't done any more checking on things other than that it now powers up and seems to be okay otherwise, but hopefully that's it. So, I've got to replace the regulator I removed, and get real good at microsurgery real fast so I can replace R723.

Longer-term I need to figure out if I want to keep this thing around once I get it patched up. I love it, but it seems like a ticking time bomb.

Still happy to hear any commentary on this and the previous analysis. Maybe all the issues I've had have something in common and fixing that would help this thing live a long life?

--Dan


On Jul 11, 2021, at 13:46, Dan Smith - KK7DS via groups.io <dsmith=danplanet.com@groups.io> wrote:

Hi all,

I'm looking for some help with my IC7000. I apologize for being wordy, it's in my nature and I can't help it. I'll provide a little background, in case it's relevant. If not, just skip to the problem description.

=== Background ===

I've used it quite a bit off an on over the years, but we have a bit of a dysfunctional relationship. I used to use it for a lot of portable (early days of SOTA) work in all kinds of conditions. It never got really wet or anything, and doesn't show any corrosion anywhere, but it has been outside quite a bit. Many years ago, it started doing this thing where it would just go deaf (all HF bands at least) on and off. Like, it would be sitting there in RX, showing S5 background noise, then ... silent S0 for ten minutes or so, then back to S5 like nothing happened. No touching, no external stimulus. I made a private youtube video showing it happen, wrote up a bunch of diagnosis and details, and sent it to Icom. They called me back, saying that they couldn't reproduce the problem, refused to look at the video, and thus were just sending it back to me with the ribbon cables reseated. I was super frustrated with this response (it was actually worse than I describe), so when I got it back, I literally put it on a shelf. A couple years later, I pulled it out to use it and got just the click-click-of-death thing. Back on the shelf, but later I diagnosed the shorted tantalum cap in the head, replaced, and it would power up. Back on the shelf without much use. Recently got it back out, and spent a day working it pretty hard on several bands and was thrilled to have my old friend back. Until it let me down again. On to the problem description:

=== Problem Description ===

Yesterday while working it, it started to power off when I would transmit. At one point it got into a really weird reboot loop where the relay that clicks on when you power it up would click on and off, on and off whenever it had external power. Click, click, click .. until I pull the power cable. No head input would stop it. Left it unplugged for a while and then it powered back on normally. Worked it for another hour and then it shut off again during transmit -- for would be the last time. After this, I get no click-click when I hit the power button, no activity at all when it is given power. Just totally dead like a brick. No burning smell either, for what it's worth.

=== Diagnosis ===

After much pouring over the service manual and tracing things out inside, I arrived at the IC1251 3.3v regulator on the logic unit. This (AFAICT) takes the 14v HV line and regulates it down to 3.3v to power the CPU and is required for the PWRK circuit to initiate the startup. This regulator was showing about 2.7v on the input and 2.4v on the output leg. Confirmed on the head connector pin 2 (with the head detached) that it's sitting at 2.4v instead of what I would expect to be 3.3v. I can probe the HV line on the main board right by the connector that feeds the logic board, and see that it sits at 14v when the logic board is out, and drops to 3.7v or so with the logic board in place. This indicates to me that something on the logic board is pulling that down real far.

I did what I could to check the bypass caps along the input and output lines to that regulator, but they're, uh, real small and stuff. So, I decided that a sane course of action would be to pop the regulator out so I could isolate before and after it. I got it out clean (although I pulled a leg off it so I'll have to replace that at least). As soon as I did, the HV line went back up to 14v, so I was hopeful that the regulator was bad. However, I wedged a TO-220 3.3v regulator from my parts box into the spot just to test, and it does the same thing. Without the output leg of the regulator connected to the board, it sits at 3.3v and the input sits at 14v. When I connect it to the output pad, it drops down and pulls the input with it, just like the original one.

As I mentioned, I tried to check what I could that is downstream of that regulator, specifically bypass caps C1252, C1317, C1317 although the latter two are so dang small I have no idea if I'm really on them. But, they don't seem to be shorted, best I can tell. The battery diode D1301 seems fine, and the battery voltage is 3.1v. Other than that, I'm at a bit of a dead end.

I assume I'm correct that ~2.4v at the head connector and output of the regulator is too low, and that the input shouldn't be pulled down that low, if not for something drawing a lot of current. Is that correct?

What else could I reasonably do to poke? Wild guesses, as well as informed ones, are welcomed.

Thanks!

--Dan







Re: Help me fix my latest IC7000 failure

Dan Smith - KK7DS
 

Unfortunately, the saga continues. Would love some ideas on next steps.

After DigiKey and FedEx conspired against me, I finally received the replacement regulator and resistor that I needed to get the radio back together. I did that, and it happily powers up and seems to behave like normal -- on receive.

Now, when I transmit, I get weird behavior. On SSB with no modulation, power output reads almost half scale. However, on RTTY I get about 80% with RF power set to 100%.

The "power out with no modulation" behavior on SSB makes me think of self-oscillation, but I don't think it explains the RTTY "not full power" behavior. I pulled the covers off and re-sprung the ground springy things, but no difference. I wonder if the microprocessor resistor failure was actually a secondary effect of something in the TX path...

Any ideas?

--Dan

On Jul 11, 2021, at 9:37 PM, Dan Smith - KK7DS via groups.io <dsmith=danplanet.com@groups.io> wrote:

Well, sorry to be that guy that replies to his own emails. Further analysis for the archives:

I think I've got it worked out. Initially I was assuming there was something on the logic board that was drawing down the 3.3v line. So, I tried feeding the regulator input directly with the logic board not seated in the main board. That worked fine, with the regulator output at 3.3v and the input holding where I was feeding it. So, I thought maybe it was something on the main board drawing it to ground between the logic board connector and the head connector. There was no path to ground between pin 2 on the head connector that I could measure, so I seated the logic board back in the main board, with the main DC power disconnected and direct-fed the regulator on the logic board again. With that, I got a solid 3.3v at the head connector. However, if I powered the unit through the main DC connector, I'd get the same deal: low regulator HV input line, low regulator output, and low voltage at the head connector.

This led to me to think there was a high resistance in the path feeding the HV line. With no load, it would measure 14v, but under load it would draw down. I traced that to the PA board, where the HV line passes through EP703 (RFI choke I think) and R723, which I assume is a current limiting resistor to protect the always-on HV line. Measuring in-circuit, the choke was zero ohms (as expected), and R723 measured 52 ohms. It's marked in the service manual as 4.7. So, I bypassed R723 with a big and ugly 1/4 watt resistor of the lowest value from my stash (10 ohm) and...IT WORKED.

I haven't done any more checking on things other than that it now powers up and seems to be okay otherwise, but hopefully that's it. So, I've got to replace the regulator I removed, and get real good at microsurgery real fast so I can replace R723.

Longer-term I need to figure out if I want to keep this thing around once I get it patched up. I love it, but it seems like a ticking time bomb.

Still happy to hear any commentary on this and the previous analysis. Maybe all the issues I've had have something in common and fixing that would help this thing live a long life?

--Dan


On Jul 11, 2021, at 13:46, Dan Smith - KK7DS via groups.io <dsmith=danplanet.com@groups.io> wrote:

Hi all,

I'm looking for some help with my IC7000. I apologize for being wordy, it's in my nature and I can't help it. I'll provide a little background, in case it's relevant. If not, just skip to the problem description.

=== Background ===

I've used it quite a bit off an on over the years, but we have a bit of a dysfunctional relationship. I used to use it for a lot of portable (early days of SOTA) work in all kinds of conditions. It never got really wet or anything, and doesn't show any corrosion anywhere, but it has been outside quite a bit. Many years ago, it started doing this thing where it would just go deaf (all HF bands at least) on and off. Like, it would be sitting there in RX, showing S5 background noise, then ... silent S0 for ten minutes or so, then back to S5 like nothing happened. No touching, no external stimulus. I made a private youtube video showing it happen, wrote up a bunch of diagnosis and details, and sent it to Icom. They called me back, saying that they couldn't reproduce the problem, refused to look at the video, and thus were just sending it back to me with the ribbon cables reseated. I was super frustrated with this response (it was actually worse than I describe), so when I got it back, I literally put it on a shelf. A couple years later, I pulled it out to use it and got just the click-click-of-death thing. Back on the shelf, but later I diagnosed the shorted tantalum cap in the head, replaced, and it would power up. Back on the shelf without much use. Recently got it back out, and spent a day working it pretty hard on several bands and was thrilled to have my old friend back. Until it let me down again. On to the problem description:

=== Problem Description ===

Yesterday while working it, it started to power off when I would transmit. At one point it got into a really weird reboot loop where the relay that clicks on when you power it up would click on and off, on and off whenever it had external power. Click, click, click .. until I pull the power cable. No head input would stop it. Left it unplugged for a while and then it powered back on normally. Worked it for another hour and then it shut off again during transmit -- for would be the last time. After this, I get no click-click when I hit the power button, no activity at all when it is given power. Just totally dead like a brick. No burning smell either, for what it's worth.

=== Diagnosis ===

After much pouring over the service manual and tracing things out inside, I arrived at the IC1251 3.3v regulator on the logic unit. This (AFAICT) takes the 14v HV line and regulates it down to 3.3v to power the CPU and is required for the PWRK circuit to initiate the startup. This regulator was showing about 2.7v on the input and 2.4v on the output leg. Confirmed on the head connector pin 2 (with the head detached) that it's sitting at 2.4v instead of what I would expect to be 3.3v. I can probe the HV line on the main board right by the connector that feeds the logic board, and see that it sits at 14v when the logic board is out, and drops to 3.7v or so with the logic board in place. This indicates to me that something on the logic board is pulling that down real far.

I did what I could to check the bypass caps along the input and output lines to that regulator, but they're, uh, real small and stuff. So, I decided that a sane course of action would be to pop the regulator out so I could isolate before and after it. I got it out clean (although I pulled a leg off it so I'll have to replace that at least). As soon as I did, the HV line went back up to 14v, so I was hopeful that the regulator was bad. However, I wedged a TO-220 3.3v regulator from my parts box into the spot just to test, and it does the same thing. Without the output leg of the regulator connected to the board, it sits at 3.3v and the input sits at 14v. When I connect it to the output pad, it drops down and pulls the input with it, just like the original one.

As I mentioned, I tried to check what I could that is downstream of that regulator, specifically bypass caps C1252, C1317, C1317 although the latter two are so dang small I have no idea if I'm really on them. But, they don't seem to be shorted, best I can tell. The battery diode D1301 seems fine, and the battery voltage is 3.1v. Other than that, I'm at a bit of a dead end.

I assume I'm correct that ~2.4v at the head connector and output of the regulator is too low, and that the input shouldn't be pulled down that low, if not for something drawing a lot of current. Is that correct?

What else could I reasonably do to poke? Wild guesses, as well as informed ones, are welcomed.

Thanks!

--Dan





Re: Stays in Transmit

Steve Norris W5KI
 

Thanks JD.  WIth my not so young eyes, hands, etc ... it's probably going to be too deep a dive.  I will check the suggestions made here, including yours....  and decide as I find some of those answers.  I've done some SMD on things like a Steppir controller, etc.  But going too far into the 7000 is likely beyond my comfort range.

Steve, W5KI

On 7/20/2021 1:18 PM, J.D. Barron wrote:
How serious are you about digging into the IC-7000?
Are you comfortable working on little bitty SMD devices and taking the radio apart?
I ask because working all through the drawings and troubleshooting does take a bit of effort.
The schematics are posted here I believe and tracking down the suggestion on the pull up resistor is a good start. 
However if the tracking is not going to be productive...
You could check the voltage on the PTT line on the accessory plug. If it is not high there then it can't be high deeper in the radio.
The same would apply to the mike PTT on the front and back. 
Data socket pin 3, Acc socket pin 3 HSEND pin 7 VSEND.
Pin 9 on the acc is the key line to the AT-180.
I think pin 6 on the mike jack.
The most likely points of failure are where the radio communicated with the outside world.


Re: Stays in Transmit

 

How serious are you about digging into the IC-7000?
Are you comfortable working on little bitty SMD devices and taking the radio apart?
I ask because working all through the drawings and troubleshooting does take a bit of effort.
The schematics are posted here I believe and tracking down the suggestion on the pull up resistor is a good start. 
However if the tracking is not going to be productive...
You could check the voltage on the PTT line on the accessory plug. If it is not high there then it can't be high deeper in the radio.
The same would apply to the mike PTT on the front and back. 
Data socket pin 3, Acc socket pin 3 HSEND pin 7 VSEND.
Pin 9 on the acc is the key line to the AT-180.
I think pin 6 on the mike jack.
The most likely points of failure are where the radio communicated with the outside world.


Re: Stays in Transmit

Steve Norris W5KI
 

Thanks to all three replies.

W3AHL:  Yes, all the in shack cable, inter-connections between rigs, PC, accessories were connected.

KE1B:  No, it is literally in transmit mode.  Red LED and no receive at any time.  PTT as if it is keyed.  FM/RTTY, if selected sends out signal.  CW sends out signal properly when paddle pressed, but not break-in, like semi, always in TX mode.

IW0HEX:  Thanks for idea.  Will work through checking that possibility.

Steve, W5KI


Re: Stays in Transmit

Pasquale S
 

Some times ago I repaird an IC-7000 with the same iusse, Led TX Red always on.

The owner said me that issue was during a storm with lightning and he used a item link on ACC port. I thought there is a issue on logic board and it was right.

Check on SEND line to ACC port from logic board (CPU), you will find a pullup resistor; I found this resistor opened so SEND line in RX wasn’t on 5 volt but 0 and the result was LED TX on.

Sorry for my english.

Regards

Pasquale IW0HEX

 

 

Sent from Mail for Windows 10

 

From: Steve Norris W5KI
Sent: lunedì 19 luglio 2021 21:06
To: ic7000@groups.io
Subject: [ic7000] Stays in Transmit

 

Hi.  Looked for any past posts, but didn't find them. 

Before the problem below developed, all control cables and coax disconnected (due to approaching storms), I have a disconnect area outside the house about 20 feet away.  I place the "house" bundle about 2 feet way from antenna area bundle of coax and various control lines to rotor, switches, etc.  SUSTAINED a lightning strike on the densely wooded hill behind me, may have hit an antenna, all 150 feet away.  But you could smell burnt wood, so some tree was hit.  Steep, rocky climb so not been up there yet. 

Results:  Wire damage and blown connector to the outdoor phone cable used.  This at the "disconnected end" of that remote switch run.  No other visible damage.  Inside, besides coming out of the chair from sound/flash from strike, no visible damage.  The lights barely blinked.  Multiple TVs, electronics in the house, and ALMOST all the equipment in the shack is still fine.  (1) The station PC is dead.  YES ... audio, data, etc cables, connect EVERYTHING else in the shack to that PC.  Not the power supply, so the motherboard and beyond suspected.  

But to the point, (2) the backup IC-7000 TX light stays lit RED, no sound out of speakers.   Output is fine.  CW keys.  SSB voice peaks show.  RTTY & FM go to normal power out.  All navigation through menus is normal.  I did a hard reset but same situation after that.  All connectors to the rig removed except for antenna coax -- and key during CW test, and Mic just for SSB test.

Any ideas?  Since all functioning of the unit otherwise looks good, power, processor, etc. ...  I hate to send it off before asking here.  Thanks.

Steve, W5KI

 


Re: Stays in Transmit

Rich Seifert
 

On Jul 19, 2021, at 10:38 AM, Steve Norris W5KI <w5ki@silverlarkcrafts.com> wrote:

Hi. Looked for any past posts, but didn't find them.

Before the problem below developed, all control cables and coax disconnected (due to approaching storms), I have a disconnect area outside the house about 20 feet away. I place the "house" bundle about 2 feet way from antenna area bundle of coax and various control lines to rotor, switches, etc. SUSTAINED a lightning strike on the densely wooded hill behind me, may have hit an antenna, all 150 feet away. But you could smell burnt wood, so some tree was hit. Steep, rocky climb so not been up there yet.

Results: Wire damage and blown connector to the outdoor phone cable used. This at the "disconnected end" of that remote switch run. No other visible damage. Inside, besides coming out of the chair from sound/flash from strike, no visible damage. The lights barely blinked. Multiple TVs, electronics in the house, and ALMOST all the equipment in the shack is still fine. (1) The station PC is dead. YES ... audio, data, etc cables, connect EVERYTHING else in the shack to that PC. Not the power supply, so the motherboard and beyond suspected.

But to the point, (2) the backup IC-7000 TX light stays lit RED, no sound out of speakers. Output is fine. CW keys. SSB voice peaks show. RTTY & FM go to normal power out. All navigation through menus is normal. I did a hard reset but same situation after that. All connectors to the rig removed except for antenna coax -- and key during CW test, and Mic just for SSB test.

Any ideas? Since all functioning of the unit otherwise looks good, power, processor, etc. ... I hate to send it off before asking here. Thanks.

Steve, W5KI
Is it just the LIGHT that stays red, i.e., can you RECEIVE (even though the TX light is red), and does PTT (or CW break-in) toggle between TX and RX properly? If so, it may be just an annoyance (perhaps the transistor that drives the LED to ground is shorted) and can be ignored.

Rich KE1B


Re: Stays in Transmit

Steve W3AHL
 

Were cables still connected to the 7K from the PC during the storm?  Which ones?

Steve, W3AHL


Stays in Transmit

Steve Norris W5KI
 

Hi.  Looked for any past posts, but didn't find them. 

Before the problem below developed, all control cables and coax disconnected (due to approaching storms), I have a disconnect area outside the house about 20 feet away.  I place the "house" bundle about 2 feet way from antenna area bundle of coax and various control lines to rotor, switches, etc.  SUSTAINED a lightning strike on the densely wooded hill behind me, may have hit an antenna, all 150 feet away.  But you could smell burnt wood, so some tree was hit.  Steep, rocky climb so not been up there yet. 

Results:  Wire damage and blown connector to the outdoor phone cable used.  This at the "disconnected end" of that remote switch run.  No other visible damage.  Inside, besides coming out of the chair from sound/flash from strike, no visible damage.  The lights barely blinked.  Multiple TVs, electronics in the house, and ALMOST all the equipment in the shack is still fine.  (1) The station PC is dead.  YES ... audio, data, etc cables, connect EVERYTHING else in the shack to that PC.  Not the power supply, so the motherboard and beyond suspected.  

But to the point, (2) the backup IC-7000 TX light stays lit RED, no sound out of speakers.   Output is fine.  CW keys.  SSB voice peaks show.  RTTY & FM go to normal power out.  All navigation through menus is normal.  I did a hard reset but same situation after that.  All connectors to the rig removed except for antenna coax -- and key during CW test, and Mic just for SSB test.

Any ideas?  Since all functioning of the unit otherwise looks good, power, processor, etc. ...  I hate to send it off before asking here.  Thanks.

Steve, W5KI



Re: Help me fix my latest IC7000 failure

Dan Smith - KK7DS
 

Whilst I had the top cover off I applied a slight pressure to various places on the boards but in particular to the logic board. What I found was that by applying a firm pressure to the corner of the logic board that is nearest to the two ribbons (closest right hand side when looking from the front of the radio) the problem went away and the radio performed as it should. I then pulled off the logic board and cleaned the two sets of contacts underneath but to no avail. I will investigate further when time permits but for now I have placed a small piece of rubber on top of the logic board so that the cover, when screwed down, places some permanent pressure.
The radio is working well at the moment but I know that in time I will need to look for a dry joint, bad track or the likes on the boards in that area to make a permanent repair. At least for now I have my right arm back. I mention all this because you are open to looking for areas to poke - Good Luck -
Thanks, that's a good tip. Those ribbon cables seem like a disaster waiting to happen. I've now un-seated and re-seated them several times in the process of checking things on both sides of the main board and I can tell they won't tolerate much more of it. They're incredibly delicate, so I guess I shouldn't be surprised that the connectors are prone to failure as well :/

--Dan


Re: Help me fix my latest IC7000 failure

Dan Smith - KK7DS
 

Well, sorry to be that guy that replies to his own emails. Further analysis for the archives:

I think I've got it worked out. Initially I was assuming there was something on the logic board that was drawing down the 3.3v line. So, I tried feeding the regulator input directly with the logic board not seated in the main board. That worked fine, with the regulator output at 3.3v and the input holding where I was feeding it. So, I thought maybe it was something on the main board drawing it to ground between the logic board connector and the head connector. There was no path to ground between pin 2 on the head connector that I could measure, so I seated the logic board back in the main board, with the main DC power disconnected and direct-fed the regulator on the logic board again. With that, I got a solid 3.3v at the head connector. However, if I powered the unit through the main DC connector, I'd get the same deal: low regulator HV input line, low regulator output, and low voltage at the head connector.

This led to me to think there was a high resistance in the path feeding the HV line. With no load, it would measure 14v, but under load it would draw down. I traced that to the PA board, where the HV line passes through EP703 (RFI choke I think) and R723, which I assume is a current limiting resistor to protect the always-on HV line. Measuring in-circuit, the choke was zero ohms (as expected), and R723 measured 52 ohms. It's marked in the service manual as 4.7. So, I bypassed R723 with a big and ugly 1/4 watt resistor of the lowest value from my stash (10 ohm) and...IT WORKED.

I haven't done any more checking on things other than that it now powers up and seems to be okay otherwise, but hopefully that's it. So, I've got to replace the regulator I removed, and get real good at microsurgery real fast so I can replace R723.

Longer-term I need to figure out if I want to keep this thing around once I get it patched up. I love it, but it seems like a ticking time bomb.

Still happy to hear any commentary on this and the previous analysis. Maybe all the issues I've had have something in common and fixing that would help this thing live a long life?

--Dan

On Jul 11, 2021, at 13:46, Dan Smith - KK7DS via groups.io <dsmith=danplanet.com@groups.io> wrote:

Hi all,

I'm looking for some help with my IC7000. I apologize for being wordy, it's in my nature and I can't help it. I'll provide a little background, in case it's relevant. If not, just skip to the problem description.

=== Background ===

I've used it quite a bit off an on over the years, but we have a bit of a dysfunctional relationship. I used to use it for a lot of portable (early days of SOTA) work in all kinds of conditions. It never got really wet or anything, and doesn't show any corrosion anywhere, but it has been outside quite a bit. Many years ago, it started doing this thing where it would just go deaf (all HF bands at least) on and off. Like, it would be sitting there in RX, showing S5 background noise, then ... silent S0 for ten minutes or so, then back to S5 like nothing happened. No touching, no external stimulus. I made a private youtube video showing it happen, wrote up a bunch of diagnosis and details, and sent it to Icom. They called me back, saying that they couldn't reproduce the problem, refused to look at the video, and thus were just sending it back to me with the ribbon cables reseated. I was super frustrated with this response (it was actually worse than I describe), so when I got it back, I literally put it on a shelf. A couple years later, I pulled it out to use it and got just the click-click-of-death thing. Back on the shelf, but later I diagnosed the shorted tantalum cap in the head, replaced, and it would power up. Back on the shelf without much use. Recently got it back out, and spent a day working it pretty hard on several bands and was thrilled to have my old friend back. Until it let me down again. On to the problem description:

=== Problem Description ===

Yesterday while working it, it started to power off when I would transmit. At one point it got into a really weird reboot loop where the relay that clicks on when you power it up would click on and off, on and off whenever it had external power. Click, click, click .. until I pull the power cable. No head input would stop it. Left it unplugged for a while and then it powered back on normally. Worked it for another hour and then it shut off again during transmit -- for would be the last time. After this, I get no click-click when I hit the power button, no activity at all when it is given power. Just totally dead like a brick. No burning smell either, for what it's worth.

=== Diagnosis ===

After much pouring over the service manual and tracing things out inside, I arrived at the IC1251 3.3v regulator on the logic unit. This (AFAICT) takes the 14v HV line and regulates it down to 3.3v to power the CPU and is required for the PWRK circuit to initiate the startup. This regulator was showing about 2.7v on the input and 2.4v on the output leg. Confirmed on the head connector pin 2 (with the head detached) that it's sitting at 2.4v instead of what I would expect to be 3.3v. I can probe the HV line on the main board right by the connector that feeds the logic board, and see that it sits at 14v when the logic board is out, and drops to 3.7v or so with the logic board in place. This indicates to me that something on the logic board is pulling that down real far.

I did what I could to check the bypass caps along the input and output lines to that regulator, but they're, uh, real small and stuff. So, I decided that a sane course of action would be to pop the regulator out so I could isolate before and after it. I got it out clean (although I pulled a leg off it so I'll have to replace that at least). As soon as I did, the HV line went back up to 14v, so I was hopeful that the regulator was bad. However, I wedged a TO-220 3.3v regulator from my parts box into the spot just to test, and it does the same thing. Without the output leg of the regulator connected to the board, it sits at 3.3v and the input sits at 14v. When I connect it to the output pad, it drops down and pulls the input with it, just like the original one.

As I mentioned, I tried to check what I could that is downstream of that regulator, specifically bypass caps C1252, C1317, C1317 although the latter two are so dang small I have no idea if I'm really on them. But, they don't seem to be shorted, best I can tell. The battery diode D1301 seems fine, and the battery voltage is 3.1v. Other than that, I'm at a bit of a dead end.

I assume I'm correct that ~2.4v at the head connector and output of the regulator is too low, and that the input shouldn't be pulled down that low, if not for something drawing a lot of current. Is that correct?

What else could I reasonably do to poke? Wild guesses, as well as informed ones, are welcomed.

Thanks!

--Dan


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