Date   

Re: Dead 7603

Jim Ford
 

Thanks, Harvey.

So I checked out the 8 V supply feeding the 5 V supply - it looks really bad! Similar waveform to the 5 V rail but dips from a high of maybe 14 V down to about 2 V. That's at the junction of the cathodes of rectifiers CR820 and C821, C821, R821, and the collectors of Q829 and Q835 on the Rectifier Board.

Then I checked at the anodes of CR820 and CR821; more convenient to look across C820. I saw about a 30 Vp-p near-sinewave there, with the anode of CR820 180 degrees out of phase with the anode of CR821. That seemed OK, but the output is just wrong!

I tried to measure C821 (18,000 uF) in-circuit with my cheapo Chinese transistor/resistor/diode/capacitor checker, but it couldn't get a reading. Ditto for C820 (0.1 uF, 100 V). I assume the transformer effectively presents a short and throws off the checker.

Also, R821, from the cap/diode cathodes/transistor collectors point to GND, reads 5.5k ohms, when it's supposed to be 4.7k +/-10%. I was surprised to see it read high; most times the sneak paths make resistors read low in-circuit. Not that 5.5k probably makes a difference.

Anyway, should I suspect the cap C821 or one of the diodes CR820 or CR821? Or something else altogether?

Thanks, everybody.

Jim

------ Original Message ------
From: "Harvey White" <madyn@...>
To: TekScopes@groups.io
Sent: 7/15/2018 6:16:20 PM
Subject: Re: [TekScopes] Dead 7603

On Sun, 15 Jul 2018 23:32:06 +0000, you wrote:

OK, here's where I am now: Power light comes on, and all LV DC voltages
are within tolerance except +5 V, which reads ~+4.4 V.
suspicious

Ripple is out of
spec on all except for +130 V. +5 V rail looks like a high duty ratio
dipping from 5 V down to about 2 V periodically, synchronous with the AC
mains.
DING DING DING!

Problem here. Possible that one of two things is at fault (maybe
both, but not likely). FIRST: suspect the bulk capacitor. SECOND:
suspect the bridge rectifier. (On a 5440, had the same thing, as well
as a toasted resistor in the 15 volt supply. filter capacitor (10000
uf, 12 vols) read extremely high esr (couldn't measure), and did not
tell me what the capacitance was.)

Replacing main capacitor, will mention what the result was, bridge
tested OK.

I figured a tantalum capacitor on the 5 V rail was a nominal
short, but I don't see any tantalums anywhere in this scope, a late
model 7603, Serial Number B345179. Just ceramic discs and aluminum
electrolytics.
Could be an aluminum electrolytic, but high ripple on a supply points
you at either the main filter capacitor *or* the rectifier. I'm
betting on the capacitor.



Any ideas on where to look? I figure the crap on the 5 V rail may be
messing up the others - make sense?
The ripple may be causing all sorts of problems. Regulators do expect
voltages at their inputs that never drop below the output voltage.
(most of the ones in TEK equipment being series regulators,
effectively).


Harvey


Thanks.

Jim

------ Original Message ------
From: "Al Holt" <@wd4ah>
To: TekScopes@groups.io
Sent: 6/25/2018 4:21:40 AM
Subject: Re: [TekScopes] Dead 7603

You've got a dead 7603 with no lights. Definitely look at the low
voltages first. Check the 0.15A (150mA) fuse, F855, just because its
'filament' is so delicate it can easily become disconnected from its
end caps from heat and age. In my case this wasn't the 'magic bullet'
to fixing my 7603, but losing the 130V line kills the HV system.

Getting the front panel power indicator to light would be the next
challenge. The LV regulators are interconnected in a way that will
prevent this lamp from lighting if one of them is bad. I can't remember
how it all hangs together now, but there are a number of posts here
that spell it out.

Sorry, about being too vague, but I'm writing this from memory. I think
the LV rectifier board is going to be the key to this, and it's worth
the time to pull it, give it a visual and check the condition of the
electrolytic caps. And be sure to mark the ribbon cables as you
disassemble things!

Good luck!

--Al



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Re: 7A29 attenuator fault corrosion issue

Adrian
 

Hi George,

Glad it worked for you too! I guess you may have figured this out as well but when it comes to re-engaging the slots in the SMA connector with the stripline I found the springy stripline position seemed to be offset from centre a bit. I assume this is to ensure good contact with the slot in the pin.

I found that by leaving the screws holding the top plate slightly loose and angling the SMA plate a small amount away from the bottom plate it was possible to use the SMA plate to push down on the top plate a tiny amount and still just see (with a good light!) the end of the stripline and the slot to align them and then 'hinge' the SMA plate into position before tightening the top plate fully.

As to what caused the problem my guess is that the corrosion is galvanic in nature as it was very local to the contact area of the resistor ground connection. I couldn't figure out what that contact 'lip' was made from though - I thought it looked like some sort of elastomer in color but on mine at least it seemed pretty hard for that?

I notice there's I guy selling a dozen or so 7A29s on the 'bay tonight - 60 bucks each or offers, would be a good deal if I wasn't on the wrong side of the Atlantic these days! he has them all listed as 'TA29' for some (typographical?) reason.

Adrian

On 7/20/2018 12:53 PM, glkinst@... wrote:
As you mentioned, it is really important to remove the SMA connectors first before removing of the bottom plastic plate that has the gold-plated fingers and tabs. The tabs fit in the slot on the SMA connector. Re-assembly requires patience, don't force for it or you will damage the connection.


Re: 7A29 attenuator fault corrosion issue

cmjones01
 

On Fri, Jul 20, 2018 at 04:53 AM, <glkinst@...> wrote:
Also, I found cracks on the plastic cams on the shaft. The cams are still
secure, but I wonder if the cracks will cause problems at some point.
Yes, both of my 7A29s are like that. On one of them a couple of cams had rotated so the attenuator settings no longer made sense. I added a fillet of epoxy at each side of each cam (I used Loctite 3430 because it's what I have in the lab, but other would probably do fine) to support the cams on the shaft. Time will tell whether it works long-term, but they've been OK for a couple of years now.

Chris


Re: 7A29 attenuator fault corrosion issue

glkinst@...
 

Adrian,
I was able to restore one and now two of my 7A29 units following your procedure! It is definitely a ground contact issue between the resistors and aluminum block. One more to go. It is indeed a tedious and a delicate operation. As you mentioned, it is really important to remove the SMA connectors first before removing of the bottom plastic plate that has the gold-plated fingers and tabs. The tabs fit in the slot on the SMA connector. Re-assembly requires patience, don't force for it or you will damage the connection.

Also, I found cracks on the plastic cams on the shaft. The cams are still secure, but I wonder if the cracks will cause problems at some point.

George


Re: My "new" Tek 485 with opt 4

Reginald Beardsley
 

Not sure it will work, but I'm attaching a scan of the 465 manual pages describing the option. It's basic SMPS EMI filtering plus a mesh screen on the face of the CRT. I'm guessing the mesh screen was removed from mine at some point.


Re: My "new" Tek 485 with opt 4

Kevin Oconnor
 

My 585 manual says “with 485 EMI mod option 4 meets mil 1-618D req: power line conducted, 150khz -25mhz; radiated , 150khz-GHz [sic].
Don’t know what the mod is though. If someone knows, please post.

Sent from kjo iPhone


Re: Looking at a broken 2440

Jim Ford
 

Ah, the HP 54503A must be similar to the 400 MHz 54504A DSO that we have
unused in the storage area at work. Came from a power supply vendor who
went out of business, but we have more modern Tek TDS3034's and 3054's
to do the job it used to do, and theyr'e easily portable to boot. The
hardware lead said he wants the 54504A thrown in the trash. I said,
don't do that, give it to me for my garage lab! Would be nice to have a
digital sampling scope to "stop time". Analog scopes like my 7904, 7603
(still working on nursing that one back to health), and 5103N/D10 are
great, but since I don't want to fool with analog storage scopes, I
don't have a way to get screen persistence. Until the lab manager fills
out the paperwork - the bane of those who work for big companies like me
(Raytheon).

Jim

------ Original Message ------
From: "Kevin Oconnor" <@KO3Y>
To: TekScopes@groups.io
Sent: 7/19/2018 8:25:16 PM
Subject: Re: [TekScopes] Looking at a broken 2440

The 2440 can be a real craps shoot. I had one on the shelf for many
years that was failing self tests so bad that it would never boot to
even crippled functionality. One of the failures, as I recall, was one
of the custom ADC chips. Since I already had a 500mhz HP 54503A & a
Tek485, I sold the 2440 off as a parts mule.
I remember opening it several times trying to muster the energy to fix
it. I remain to this day amazed at the quantity of thru hole ICs on all
4 sides ! Hats off to those who are willing to work on these scopes!

Sent from kjo iPhone



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Re: Looking at a broken 2440

Kevin Oconnor
 

The 2440 can be a real craps shoot. I had one on the shelf for many years that was failing self tests so bad that it would never boot to even crippled functionality. One of the failures, as I recall, was one of the custom ADC chips. Since I already had a 500mhz HP 54503A & a Tek485, I sold the 2440 off as a parts mule.
I remember opening it several times trying to muster the energy to fix it. I remain to this day amazed at the quantity of thru hole ICs on all 4 sides ! Hats off to those who are willing to work on these scopes!

Sent from kjo iPhone


Re: OT: +19.5 V connector on laptop computers

Leon Robinson
 

I just got a 19.5 volt 45 watt HP supply today.
The connector is a large 3 contact coaxial, Positive Center pin, Negative Outside Sleve
and Voltage control on the Inside Sleeve.
Voltage measured 13.4 from Outside to Center Pin with the Inside Sleeve open.

Voltage measured 22.2 from Outside to Center Pin with the Inside Sleeve shorted to the Center Pin.
I will probably cut the connector off for my use, because the Supply will be mounted
inside the case along with the other circuitry. Leon Robinson    K5JLR

Political Correctness is a Political Disease.

From: Jeff Urban <@JURB>
To: TekScopes@groups.io
Sent: Thursday, July 19, 2018 9:12 PM
Subject: Re: [TekScopes] OT: +19.5 V connector on laptop computers

On Mon, Jul 16, 2018 at 05:08 PM, Harvey White wrote:


I've seen a standardization to several end destinations. One is that
the voltage rating seems to determine the size of the barrel
connector. That's now, from what I can see.
You mean the outer diameter ? It seems the pin is more based on the current. this laptop, I can plug its adapter into a smaller and older laptop, but the for it will not plug into this one because of the pin diameter.

I'm going to conclude that there's an evolving standard out there, and
I have no idea of what it is.

Now, that is completely screwed up by the "DELL" standard, which
apparently includes some HP laptops.

Dell has a 3 wire cable to the power supply brick. The inner pin is
apparently an I2C connector. The inner and outer shells are power and
ground (suggest that the outer is ground). In a DELL computer, if the
power block does not identify itself as a "genuine" power adaptor,
then the battery will not charge.
Typical corporate behavior.  Captive market is king. If they continue this and sell enough of them like that then a market will be created for aftermarket chargers. It is not all that difficult. Just a matter of a custom tailored current output and their batteries are not of any brand new technology that doesn't exist yet.

Those adaptors (and don't ask me what I think of them) work with a
different standard. Not sure what the effective voltage and current
limits are in this case.
That's why we have test equipment. Take all OEM parts and let them work together a couple of times, Measure everything. Would I do a one off for myself ? No, I would get rid of the thing. I almost didn't buy these Gateways but the price was right. Large screen, full keyboard and 2 HD bays. But though there are multiple connection on the batteries (I have 3 I think) but the adapter only has 2, so there is none of that captive market shit.

I  used to build all my own PCs, and some for others, but you really can't do that with a laptop.

Actually for Jim's needs, there are probably surplus VCR power supplies that would do the job. For a one off it might be free on Craigslist or whatever. They fry out but with a new chopper, sometimes another transistor and changing the caps they can definitely do the job. Inmost the 3 major caps they need are those in the pi filter for the 5 volts because it feeds the feedback loop, and there is one in the snubber without which the chopper will short. Very rarely any other parts except do change a bunch more caps.

It's a thought.


Re: OT: +19.5 V connector on laptop computers

Harvey White
 

On Thu, 19 Jul 2018 19:11:56 -0700, you wrote:

On Mon, Jul 16, 2018 at 05:08 PM, Harvey White wrote:


I've seen a standardization to several end destinations. One is that
the voltage rating seems to determine the size of the barrel
connector. That's now, from what I can see.
You mean the outer diameter ? It seems the pin is more based on the current. this laptop, I can plug its adapter into a smaller and older laptop, but the for it will not plug into this one because of the pin diameter.
The outer diameter. I've seen 6, 9 and 12 volt adaptors where the
plugs will not go into something with the "wrong" voltage requirement.
The older ones seem to standardize on one thing and it's up to you to
hit the right voltage.

I design all my stuff with polarity protection, and the voltage
limiting/protection is starting to be a design feature, too.


I'm going to conclude that there's an evolving standard out there, and
I have no idea of what it is.

Now, that is completely screwed up by the "DELL" standard, which
apparently includes some HP laptops.

Dell has a 3 wire cable to the power supply brick. The inner pin is
apparently an I2C connector. The inner and outer shells are power and
ground (suggest that the outer is ground). In a DELL computer, if the
power block does not identify itself as a "genuine" power adaptor,
then the battery will not charge.
Typical corporate behavior. Captive market is king. If they continue this and sell enough of them like that then a market will be created for aftermarket chargers. It is not all that difficult. Just a matter of a custom tailored current output and their batteries are not of any brand new technology that doesn't exist yet.
Now ask what happens if the MOTHERBOARD won't recognize a valid power
adaptor.

Now ask if I buy any more DELL computers.


Those adaptors (and don't ask me what I think of them) work with a
different standard. Not sure what the effective voltage and current
limits are in this case.
That's why we have test equipment. Take all OEM parts and let them work together a couple of times, Measure everything. Would I do a one off for myself ? No, I would get rid of the thing. I almost didn't buy these Gateways but the price was right. Large screen, full keyboard and 2 HD bays. But though there are multiple connection on the batteries (I have 3 I think) but the adapter only has 2, so there is none of that captive market shit.
Not a connection on the battery. Didn't look and didn't at that time
care. Power brick and laptop.

Harvey



I used to build all my own PCs, and some for others, but you really can't do that with a laptop.

Actually for Jim's needs, there are probably surplus VCR power supplies that would do the job. For a one off it might be free on Craigslist or whatever. They fry out but with a new chopper, sometimes another transistor and changing the caps they can definitely do the job. Inmost the 3 major caps they need are those in the pi filter for the 5 volts because it feeds the feedback loop, and there is one in the snubber without which the chopper will short. Very rarely any other parts except do change a bunch more caps.

It's a thought.



Re: OT: +19.5 V connector on laptop computers

 

On Mon, Jul 16, 2018 at 05:08 PM, Harvey White wrote:


I've seen a standardization to several end destinations. One is that
the voltage rating seems to determine the size of the barrel
connector. That's now, from what I can see.
You mean the outer diameter ? It seems the pin is more based on the current. this laptop, I can plug its adapter into a smaller and older laptop, but the for it will not plug into this one because of the pin diameter.

I'm going to conclude that there's an evolving standard out there, and
I have no idea of what it is.

Now, that is completely screwed up by the "DELL" standard, which
apparently includes some HP laptops.

Dell has a 3 wire cable to the power supply brick. The inner pin is
apparently an I2C connector. The inner and outer shells are power and
ground (suggest that the outer is ground). In a DELL computer, if the
power block does not identify itself as a "genuine" power adaptor,
then the battery will not charge.
Typical corporate behavior. Captive market is king. If they continue this and sell enough of them like that then a market will be created for aftermarket chargers. It is not all that difficult. Just a matter of a custom tailored current output and their batteries are not of any brand new technology that doesn't exist yet.

Those adaptors (and don't ask me what I think of them) work with a
different standard. Not sure what the effective voltage and current
limits are in this case.
That's why we have test equipment. Take all OEM parts and let them work together a couple of times, Measure everything. Would I do a one off for myself ? No, I would get rid of the thing. I almost didn't buy these Gateways but the price was right. Large screen, full keyboard and 2 HD bays. But though there are multiple connection on the batteries (I have 3 I think) but the adapter only has 2, so there is none of that captive market shit.

I used to build all my own PCs, and some for others, but you really can't do that with a laptop.

Actually for Jim's needs, there are probably surplus VCR power supplies that would do the job. For a one off it might be free on Craigslist or whatever. They fry out but with a new chopper, sometimes another transistor and changing the caps they can definitely do the job. Inmost the 3 major caps they need are those in the pi filter for the 5 volts because it feeds the feedback loop, and there is one in the snubber without which the chopper will short. Very rarely any other parts except do change a bunch more caps.

It's a thought.


R7103 Available (Re: [TekScopes] Looking at a broken 2440)

Artekmedia <manuals@...>
 

Speaking of the 7104 I have a very nice R7103 ( rack mount 3 slot version of 7104) that as Harvey says I no longer wonder why I need it .....I dont!!

_*Make an offer*_ , pick up ONLY in Tampa FL area. Includes 7A29, 7A19 and 7B92A P-I's. I will NOT SHIP ..dont ask

Dave
manuals@...

On 7/19/2018 9:47 PM, Harvey White wrote:
On Thu, 19 Jul 2018 14:02:28 -0700, you wrote:

I think I'm going to pass it up. I need to start being selective on my scope choices. I think my next scope will be one I really want. Which is a 2467 or 7104 with a MCP CRT.
I have a 7104. I use it only when I need the MCP or the 1 GHZ
bandwidth. That requires either a direct coax input or a 1 GHz probe
(and, for that matter, something where the bandwidth is needed).

Having one, I wouldn't give it up. Not having one, I'd wonder if I
need it. (mostly my use would be digital stuff, and looking at pulses
there. I've got an HP 16702B that helps here).

Harvey



On Thu, Jul 19, 2018 at 01:23 PM, goran parezanovich wrote:

Personally I would offer less - in addition to power supply caps and
possible damage to the traces under the caps there is a possibility
that the NVRAMs will have to be changed ( dead batteries ) .


<-----Original Message----->
From: lop pol via Groups.Io [the_infinite_penguin=yahoo.com@groups.io]
Sent: 7/19/2018 2:04:37 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Looking at a broken 2440

?I'm looking at a 2440 that won't power on for $85. Worth it or not?
What is
the likelihood of just power supply issues and no IC problems?
Thanks fellas



--
Dave
Manuals@...
www.ArtekManuals.com


Re: Looking at a broken 2440

Harvey White
 

On Thu, 19 Jul 2018 14:02:28 -0700, you wrote:

I think I'm going to pass it up. I need to start being selective on my scope choices. I think my next scope will be one I really want. Which is a 2467 or 7104 with a MCP CRT.
I have a 7104. I use it only when I need the MCP or the 1 GHZ
bandwidth. That requires either a direct coax input or a 1 GHz probe
(and, for that matter, something where the bandwidth is needed).

Having one, I wouldn't give it up. Not having one, I'd wonder if I
need it. (mostly my use would be digital stuff, and looking at pulses
there. I've got an HP 16702B that helps here).

Harvey




On Thu, Jul 19, 2018 at 01:23 PM, goran parezanovich wrote:


Personally I would offer less - in addition to power supply caps and
possible damage to the traces under the caps there is a possibility
that the NVRAMs will have to be changed ( dead batteries ) .


<-----Original Message----->
From: lop pol via Groups.Io [the_infinite_penguin=yahoo.com@groups.io]
Sent: 7/19/2018 2:04:37 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Looking at a broken 2440

?I'm looking at a 2440 that won't power on for $85. Worth it or not?
What is
the likelihood of just power supply issues and no IC problems?
Thanks fellas




Re: My "new" Tek 485 with opt 4

Artekmedia <manuals@...>
 

The 1982 catalog lists Option 04 for the 485 indeed as EMC option
-DC
manuals@...

On 7/19/2018 4:25 PM, Reginald Beardsley via Groups.Io wrote:
I just got a nicely refurbished 485 which lists "opt4" under the SN. I could find no information despite several searches. I was surprised at how little information there was at the w140.com/Tekwiki. My 465 manual says opt 4 is EMI environmental. Is that true of the 485 also?

It came with a CD of the service manual, but I'd like to get a nice hard copy original if anyone has one they are willing to part with. I can offer a 465 and RM45 manuals in good condition in exchange.


--
Dave
Manuals@...
www.ArtekManuals.com


Re: Looking at a broken 2440

Craig Cramb
 

The 2400 series digital are pretty cool. What I’ve dealt with over the years of repairing them is yes the NVRAM batteries can be failed which adds up to replacement recalibrate. . But rebuilding the PS isnt too bad. You just need all the caps. Disassemble the scope remove PS module. Disassemble the rack assembly from off the PS and then replace the caps. Yes this is a process but can work out ok. The other issue with the 2400 digital I have dealt with is the CRT being shorted out. So right now I have 4 2400 digital scopes with shorted CRT removed and disposed of. So buying a cheap scope thinking repair will be apiece of cake isn’t always true. Many hours of work and unobtainable parts can be required to fix. Which is now you have to buy two scopes to maybe fix one. I currently have a nice working 2467 in my inventory if you are deciding to go another route.


My "new" Tek 485 with opt 4

Reginald Beardsley
 

I just got a nicely refurbished 485 which lists "opt4" under the SN. I could find no information despite several searches. I was surprised at how little information there was at the w140.com/Tekwiki. My 465 manual says opt 4 is EMI environmental. Is that true of the 485 also?

It came with a CD of the service manual, but I'd like to get a nice hard copy original if anyone has one they are willing to part with. I can offer a 465 and RM45 manuals in good condition in exchange.


Re: Looking at a broken 2440

Jeff Woolsey
 

On 7/19/18 1:06 PM, lop pol via Groups.Io wrote:
I'm looking at a 2440 that won't power on for $85. Worth it or not? What is the likelihood of just power supply issues and no IC problems?
Thanks fellas
I'd say that could be likely.  I bought a 2440 at a flea market for
more, and it was stone dead when I got it home.  With the help of people
on this list, I got it running.  The archives should contain the saga. 
It has some small nits that I live with.  I bought a second one with a
self-test failure to use as a parts mule, but the fix for that failure
was trivial...  It's my go-to scope now.

--
Jeff Woolsey {{woolsey,jlw}@jlw,first.last@{gmail,jlw}}.com
Nature abhors straight antennas, clean lenses, and empty storage.
"Delete! Delete! OK!" -Dr. Bronner on disk space management
Card-sorting, Joel. -Crow on solitaire


Re: Looking at a broken 2440

Brendan
 

I think I'm going to pass it up. I need to start being selective on my scope choices. I think my next scope will be one I really want. Which is a 2467 or 7104 with a MCP CRT.

On Thu, Jul 19, 2018 at 01:23 PM, goran parezanovich wrote:


Personally I would offer less - in addition to power supply caps and
possible damage to the traces under the caps there is a possibility
that the NVRAMs will have to be changed ( dead batteries ) .


<-----Original Message----->
From: lop pol via Groups.Io [the_infinite_penguin=yahoo.com@groups.io]
Sent: 7/19/2018 2:04:37 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Looking at a broken 2440

?I'm looking at a 2440 that won't power on for $85. Worth it or not?
What is
the likelihood of just power supply issues and no IC problems?
Thanks fellas



Re: Looking at a broken 2440

goran parezanovich
 

Just remembered something - there is also a safety circuit designed to
stop powering up in the case of short for any of DC voltages rails - so
theoretically if there is a short at some other board the unit will not
start and power supply is still working correctly .

<-----Original Message----->
From: lop pol via Groups.Io [the_infinite_penguin=yahoo.com@groups.io]
Sent: 7/19/2018 2:04:37 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Looking at a broken 2440

?I'm looking at a 2440 that won't power on for $85. Worth it or not?
What is
the likelihood of just power supply issues and no IC problems?
Thanks fellas



Re: Looking at a broken 2440

goran parezanovich
 

Personally I would offer less - in addition to power supply caps and
possible damage to the traces under the caps there is a possibility
that the NVRAMs will have to be changed ( dead batteries ) .

<-----Original Message----->
From: lop pol via Groups.Io [the_infinite_penguin=yahoo.com@groups.io]
Sent: 7/19/2018 2:04:37 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Looking at a broken 2440

?I'm looking at a 2440 that won't power on for $85. Worth it or not?
What is
the likelihood of just power supply issues and no IC problems?
Thanks fellas