Date   

Re: QCX 20 No output...New build

James Daldry W4JED
 

Hi, Steve

Paul is reading a short to ground from the collector of Q6. Replacing Q6 by itself, in this situation, would lead to the spectacular destruction of a new Q6, unless he's fused his power supply.

Jim W4JED

On 1/27/19 2:31 PM, Steve in Okinawa wrote:
There have been several unexplained sudden failures of Q6, and coincidentally I am about to delete the photo of my spectacularly exploded one. You can replace it with any PNP but if suggest using one with a significantly higher current and voltage rating. Almost any beta will do the job.


Re: QCX 20 No output...New build

James Daldry W4JED
 

Hi, Paul

I wish I could lend you my Weller desoldering iron. It's a solder pencil, temperature controlled to 800 degrees F with a Curie effect thermostat, with a hollow tip and a vacuum pump. Surround the transistor leg with the tip, move it around until the wire wiggles, hit the switch on the pump and the solder goes away. Transistor falls out. No damage. Oh, well, if wishes were horses......

Anyhow - pull Q1 thru Q3. Check for short from Q6 to ground. If the short is gone, replace all 4 - Q1, Q2, Q3, Q6. Even if there is only one shorted FET, replace them all. In several thousand of these rigs that have been sold so far, I have heard of no C30's failed.

Jim W4JED

On 1/27/19 12:51 PM, Paul wrote:
Hi Jim

Well I am glad I pointed out which pin and location as it appears I was wrong in my original post thinking pin1 was the emitter.

I have had a good look around Q1 to 3 for any whiskers and can’t see any. C30 looks good as well but the right hand side is to ground, is that correct?

If it is then is the next step to source replacements for Q1 to 3 and Q6?
Will pulling any of the above in any order give any indication to which one is faulty?

All my TX tests have been done into a dummy load with power/swr bridge in line, except the first test which was into the antenna.

Paul

From: <QRPLabs@groups.io> on behalf of James Daldry W4JED <jim@...>
Reply-To: "QRPLabs@groups.io" <QRPLabs@groups.io>
Date: Sunday, 27 January 2019 at 14:58
To: "QRPLabs@groups.io" <QRPLabs@groups.io>
Subject: Re: [QRPLabs] QCX 20 No output...New build

Hi, Paul

OK. Pin 1, the collector, is shorted to ground. Either you are sorta lucky and have a wire clipping or solder whisker around Q1, 2, or 3 shorting their drains to ground, or you have one or more shorted transistors in the Q1 thru 3 bunch. It is also possible that C30 is the short, but that's grasping at straws. Most likely the fix will be replacing Q1, Q2, Q3, and Q6.

These radios have been tested outputting into both open and shorted antenna connectors without damage, but there may be a "magic" value of antenna reactance that results in excessive voltage or current in the final stage, and a few unlucky people have managed to find that reactance value. I would suggest that, once you have a full set of good transistors, that you do any testing into a couple 100 ohm 2 watt resistors in parallel. Once you have output into the resistors, put together a resistive swr bridge to check the antenna. While a bridge made up of nothing but resistors isn't a "perfect" way of testing an antenna, it's close enough for gummint work, and the radio never "sees" a match worse than 2:1 during testing, regardless of how bad the antenna is.

Jim W4JED

On 1/27/19 7:04 AM, Paul wrote:
Hi Jim

Thanks for taking the time to answer my question.
Just so I don’t make any “newbie” incorrect assumptions here is what I have done following your suggestion.
Using a separate multimeter one probe on the negative 12v input.
2nd probe checked for continuity on all 3 points of Q6 with the radio powered off.
To clarify I am looking at the back of the board with the BNC connector top left.
I think I am right with my pin layout, pin1 top, 2 middle and 3 bottom?
Readings are
Pin1 0 ohms 
Pin2 .47 ohms
Pin3 open circuit

Thanks again Paul

From: <QRPLabs@groups.io> on behalf of James Daldry W4JED <jim@...>
Reply-To: "QRPLabs@groups.io" <QRPLabs@groups.io>
Date: Saturday, 26 January 2019 at 21:05
To: "QRPLabs@groups.io" <QRPLabs@groups.io>
Subject: Re: [QRPLabs] QCX 20 No output...New build

Hi, Paul

Q6 either is open, its collector is shorted to ground, or both. Check for zero ohms to ground from the collector. It should check open. If short, you either have a "whisker" short or one or more shorted FET's. If the collector reads shorted to ground pull the FET's and see if the short goes away. Once the short is cleared you'll need to replace Q6.

Jim W4JED

On 1/26/19 3:19 PM, paul.hadfield@... wrote:
This is the first kit of any kind I have built and everything has been a vertical learning curve.
On completion everything appears to work as expected just no power out.
I have checked continuity and re soldered all toroids, and they are fine.
Using the built in power meter I have checked for output at Q1,2 and 3 as suggested in the manual. No output at these points.
Having spent most of Saturday afternoon searching through posts to point me in the right direction I have been looking at the voltages with Q6.
Now I think something is wrong here but but not sure, and don't know where to begin correcting the situation if it is wrong.
Using the built in V meter I am seeing
Pin1 Emmiter , 11.45v key on or off
Pin2 Base, 11.1v key off and 7.46v keydown
Pin3 Collector 0v key on or off.

Any help would be appreciated as I would love to get it all working 100%

Paul


Re: PA 10 HF linear

ajparent1/KB1GMX
 

On Sun, Jan 27, 2019 at 11:35 AM, Jerry Gaffke wrote:
When you get around to driving that amp with some RF, here's a few notes:
Gain of this amp has been said to be around 26dB, equally divided between the BS170 driver
and IRF510 final.  We expect an output of 10watts = 10*log10(10000mw/1mw) = 40dBm.
Drive into the amp should be around  40dBm - 26dB = 14dBm  =  10**(14/10) = 25mW,
but that must be efficiently coupled into the roughly 200 ohm input impedance
(not measured, and will vary with frequency) of the BS170 driver.<<<<

There are  few errors there. While the amp was designed for a geater than 50ohm
driver to make the prospective driver happy driving it at 50 ohms has relatively little
loss.

At around 7 mhx the input impedance is roughly 200 ohms and for a 50 ohm driver the 
load SWR is only 4:1, there are a few yabuts...

First the MOSFET (BS170) driver is a voltage driven system so however you impress the needed 
voltage you get the power out.  The lower impedance is the result of two already built in resistors
to manage stability, gain, and input impedance.

Second the power loss assumed by many is based on conjugate match and which is harder
to define.  As it happens a lower impedance driver into a higher impedance load has less loss
than is expected. Typically less than 3db. The reason is that most low impedance drivers are
class A and the output voltage is not greatly load sensitive when one deviates from 50 ohms
especially to the higher impedance.

Adding  parallel resistor is mostly for heating the resistor.  It does not improve the performance
of the system as to gain or any other direct parameter unless the pre-driver has issues or
odd requirements.

FYI: typical pre-driver stages at that (under 100mW) level are often built for 100-200 ohms
and its been discussed since MOSFETs are typically capacitive loads the input impedance
will vary considerably from the 1.8 to 29.999mhz design range.  So 200 ohms was a median
value for acceptable R,jx total.  Simplistic assumptions work for spot frequencies but over wide
bandwidths analysis requires a more critical evaluation.

However none of this solves Toni's basic issues.  That requires a critical examination of the
assembly for shorts, misplaced parts or even a missing one.  The board is very compact
and a solder whisker can produce hard to see defects.

Allison




Re: Battery icon

Curt M.
 

Here is picture of where to jumper 


Re: Battery icon

Ken Graham <k5id@...>
 

Need to jumper pin 1 to the pin 3 to get the battery level, as stated in the manual. These are the pins above and below the”rf and voltmeter” pin. Ken.  k5id


On Jan 27, 2019, at 1:38 PM, Steve in Okinawa <sfab43@...> wrote:

I have the same problem. My qcx works perfectly, except that the battery icon is always "hollow", and the S-meter icon disappears after i make any other setting change. Possibly these are related issues? 
 JS6TMW


Re: QCX 20 No output...New build

Paul
 

Thanks for your input Steve.

Am I right in thinking that if I pull Q6 out and the hole for pin1 is open circuit then Q6 is definitely my issue?

Paul 

From: <QRPLabs@groups.io> on behalf of Steve in Okinawa <sfab43@...>
Reply-To: "QRPLabs@groups.io" <QRPLabs@groups.io>
Date: Sunday, 27 January 2019 at 19:31
To: "QRPLabs@groups.io" <QRPLabs@groups.io>
Subject: Re: [QRPLabs] QCX 20 No output...New build

There have been several unexplained sudden failures of Q6, and coincidentally I am about to delete the photo of my spectacularly exploded one. You can replace it with any PNP but if suggest using one with a significantly higher current and voltage rating. Almost any beta will do the job.


Re: I Burned Up My U3S

Brian Summers
 

Let me suggest a preventive measure. Obtain the 5V supply from an LM7805 regulator mounted where the power input is for your U3S. I have it bolted to the DB-9 connector on the rear of the custom case. 

The majority of us use 12V power supplies in the radio room so this is a no brainer. It also has the benefit of providing a clean well regulated 5V for the U3S. I would also recommend a diode in series with the regulator, 1N4001 or similar, to protect against reverse voltage.

No prizes for guessing why mine are configured this way........

Brian VE7JKZ



On 1/27/2019 7:45 AM, n0mpm wrote:
Thanks for the hints.  Hans’ FAQ info was reassuring that all is not lost!  I am planning to flash a new ATMega and hoping that will do the trick.  
mike


Re: PA 10 HF linear

ajparent1/KB1GMX
 

Review your soldering and parts placement.


Allison


Battery icon

Steve in Okinawa
 

I have the same problem. My qcx works perfectly, except that the battery icon is always "hollow", and the S-meter icon disappears after i make any other setting change. Possibly these are related issues? 
 JS6TMW


Re: PA 10 HF linear

Jerry Gaffke
 

I didn't measure it accurately, but the analog meter on my 12.0 vdc power supply
showed around 15ma when I first powered up, this rose to around 60ma when TX was grounded.
The difference of roughly 60-15=45ma was due to the BS170 quiescent current in the driver,
I saw about 2.7v on the BS170 gates. 

Looking at the BS170 biasing circuit, I'd expect the total quiescent current through
the BS170's to be 3*0.7vbe/33ohms = 64ma, not the 45ma I wrote down.
My power supply meter could well have been off by that much.

I suggest you leave R211 and R215 fully counter-clockwise (minimum) until you figure out 
where that extra 200ma is going.
Does the current fall to around 15ma when you do not have TX grounded?
Is anything getting hot (especially the BS170's in the driver, the 7805 regulator, the IRF510's)?
The gates of the IRF510's should both be zero volts dc, are they?
What voltage do you see on the gates of the BS170's in the driver?

When you get around to driving that amp with some RF, here's a few notes:
Gain of this amp has been said to be around 26dB, equally divided between the BS170 driver
and IRF510 final.  We expect an output of 10watts = 10*log10(10000mw/1mw) = 40dBm.
Drive into the amp should be around  40dBm - 26dB = 14dBm  =  10**(14/10) = 25mW,
but that must be efficiently coupled into the roughly 200 ohm input impedance
(not measured, and will vary with frequency) of the BS170 driver.

Most of us will just put a 68 ohm resistor across the input in parallel with that 200 ohms,
so our source of RF will see a load of 68*200/(68+200) = 50 ohms.
And then increase the drive up from 25mW to compensate for the loss of power
in the 68 ohm resistor.  The 68 ohm resistor will draw about   200/68 = 3 times
as much current as the 200 ohm resistor, and thus three times as much of the
available power.  Total power from the exciter is thus 4 times what goes into
the 200 ohm driver stage, so about 4*25mw = 100mW for 10 watts out.
I have not yet made careful measurements of my power gain at various
frequencies, but that should be in the ballpark.

Be careful that the big nut used as a spacer between the board and the heatsink
does not short out the cathode 1n4004 diode.  Turn that nut such that a flat edge
faces the diode.  Though if it were shorted, I'd expect this to cut BS170 bias current
from my 45ma (or 64ma) down to zero, without damaging anything.

Jerry, KE7ER


On Sun, Jan 27, 2019 at 10:16 AM, Toni Cossio wrote:
I have completed the assembly of the "PA 10 HF linear".
I proceeded to calibrate the two trimmer R211 and R215, adjusted completely to the left as indicated in the manual.
I connected "/ TX" to GND immediately obtaining a reading of  260 mA, so without the possibility of making any adjustment on each single trimmer.
You can give me some information to correct any errors.
Thanks for your help.
73 de IV3XHM, Antonio Cossio


Re: QCX 20 No output...New build

Steve in Okinawa
 

There have been several unexplained sudden failures of Q6, and coincidentally I am about to delete the photo of my spectacularly exploded one. You can replace it with any PNP but if suggest using one with a significantly higher current and voltage rating. Almost any beta will do the job.


PA 10 HF linear

Toni Cossio
 

I have completed the assembly of the "PA 10 HF linear".
I proceeded to calibrate the two trimmer R211 and R215, adjusted completely to the left as indicated in the manual.
I connected "/ TX" to GND immediately obtaining a reading of  260 mA, so without the possibility of making any adjustment on each single trimmer.
You can give me some information to correct any errors.
Thanks for your help.
73 de IV3XHM, Antonio Cossio


Re: QCX 20 No output...New build

Paul
 

Hi Jim

Well I am glad I pointed out which pin and location as it appears I was wrong in my original post thinking pin1 was the emitter.

I have had a good look around Q1 to 3 for any whiskers and can’t see any. C30 looks good as well but the right hand side is to ground, is that correct?

If it is then is the next step to source replacements for Q1 to 3 and Q6?
Will pulling any of the above in any order give any indication to which one is faulty?

All my TX tests have been done into a dummy load with power/swr bridge in line, except the first test which was into the antenna.

Paul

From: <QRPLabs@groups.io> on behalf of James Daldry W4JED <jim@...>
Reply-To: "QRPLabs@groups.io" <QRPLabs@groups.io>
Date: Sunday, 27 January 2019 at 14:58
To: "QRPLabs@groups.io" <QRPLabs@groups.io>
Subject: Re: [QRPLabs] QCX 20 No output...New build

Hi, Paul

OK. Pin 1, the collector, is shorted to ground. Either you are sorta lucky and have a wire clipping or solder whisker around Q1, 2, or 3 shorting their drains to ground, or you have one or more shorted transistors in the Q1 thru 3 bunch. It is also possible that C30 is the short, but that's grasping at straws. Most likely the fix will be replacing Q1, Q2, Q3, and Q6.

These radios have been tested outputting into both open and shorted antenna connectors without damage, but there may be a "magic" value of antenna reactance that results in excessive voltage or current in the final stage, and a few unlucky people have managed to find that reactance value. I would suggest that, once you have a full set of good transistors, that you do any testing into a couple 100 ohm 2 watt resistors in parallel. Once you have output into the resistors, put together a resistive swr bridge to check the antenna. While a bridge made up of nothing but resistors isn't a "perfect" way of testing an antenna, it's close enough for gummint work, and the radio never "sees" a match worse than 2:1 during testing, regardless of how bad the antenna is.

Jim W4JED

On 1/27/19 7:04 AM, Paul wrote:
Hi Jim

Thanks for taking the time to answer my question.
Just so I don’t make any “newbie” incorrect assumptions here is what I have done following your suggestion.
Using a separate multimeter one probe on the negative 12v input.
2nd probe checked for continuity on all 3 points of Q6 with the radio powered off.
To clarify I am looking at the back of the board with the BNC connector top left.
I think I am right with my pin layout, pin1 top, 2 middle and 3 bottom?
Readings are
Pin1 0 ohms 
Pin2 .47 ohms
Pin3 open circuit

Thanks again Paul

From: <QRPLabs@groups.io> on behalf of James Daldry W4JED <jim@...>
Reply-To: "QRPLabs@groups.io" <QRPLabs@groups.io>
Date: Saturday, 26 January 2019 at 21:05
To: "QRPLabs@groups.io" <QRPLabs@groups.io>
Subject: Re: [QRPLabs] QCX 20 No output...New build

Hi, Paul

Q6 either is open, its collector is shorted to ground, or both. Check for zero ohms to ground from the collector. It should check open. If short, you either have a "whisker" short or one or more shorted FET's. If the collector reads shorted to ground pull the FET's and see if the short goes away. Once the short is cleared you'll need to replace Q6.

Jim W4JED

On 1/26/19 3:19 PM, paul.hadfield@... wrote:
This is the first kit of any kind I have built and everything has been a vertical learning curve.
On completion everything appears to work as expected just no power out.
I have checked continuity and re soldered all toroids, and they are fine.
Using the built in power meter I have checked for output at Q1,2 and 3 as suggested in the manual. No output at these points.
Having spent most of Saturday afternoon searching through posts to point me in the right direction I have been looking at the voltages with Q6.
Now I think something is wrong here but but not sure, and don't know where to begin correcting the situation if it is wrong.
Using the built in V meter I am seeing
Pin1 Emmiter , 11.45v key on or off
Pin2 Base, 11.1v key off and 7.46v keydown
Pin3 Collector 0v key on or off.

Any help would be appreciated as I would love to get it all working 100%

Paul


Re: Group storage

TrueBlue
 

On Sat, Jan 26, 2019 at 02:05 PM, Chopper wrote:
> Like this: https://i.imgur.com/pj8eVJS.png"

I am not a fan of this as I would never open this tiny url type link as way too many contain viruses
It's not a TinyURL link,  It's directly to Imgur's site and it's a .PNG file.


Re: Prog Rock board voltages

Alan G4ZFQ
 

My only remaining question is whether the decreased resistance at R2 will negatively affect anything else.
Hans says the higher voltages have never been known to do any harm, give a little more power out when used in the U3. (I have wondered how little.)
On the other hand I use a 1.8V TCXO with a maximum rating of 3.3V so I have reduced voltage further so my 3.3V is actually 3.1.
I have never thought this a problem.

73 Alan G4ZFQ


Re: Prog Rock board voltages

KI7MWA
 

So, just for fun, I added a 47KOhm resistor in parallel with the 3K at position R2 (for a net of 2.82K, theoretically). The fitted resistances are now 0.968K and 2.66K, and the board voltages are 5.15V and 3.57V.

My only remaining question is whether the decreased resistance at R2 will negatively affect anything else.


Re: I Burned Up My U3S

n0mpm
 

Thanks for the hints.  Hans’ FAQ info was reassuring that all is not lost!  I am planning to flash a new ATMega and hoping that will do the trick.  
mike


Re: Group storage

jjpurdum
 

It's $10/month, or $110 for a year for 10Gb.

Jack, W8TEE

On Sunday, January 27, 2019, 4:47:25 AM EST, Alan Richmond <richmond@...> wrote:


Is the cost of extra storage a one-off cost, or an annual one?

Alan

GU3ONJ


E & O E





Re: QCX 20 No output...New build

James Daldry W4JED
 

Hi, Paul

OK. Pin 1, the collector, is shorted to ground. Either you are sorta lucky and have a wire clipping or solder whisker around Q1, 2, or 3 shorting their drains to ground, or you have one or more shorted transistors in the Q1 thru 3 bunch. It is also possible that C30 is the short, but that's grasping at straws. Most likely the fix will be replacing Q1, Q2, Q3, and Q6.

These radios have been tested outputting into both open and shorted antenna connectors without damage, but there may be a "magic" value of antenna reactance that results in excessive voltage or current in the final stage, and a few unlucky people have managed to find that reactance value. I would suggest that, once you have a full set of good transistors, that you do any testing into a couple 100 ohm 2 watt resistors in parallel. Once you have output into the resistors, put together a resistive swr bridge to check the antenna. While a bridge made up of nothing but resistors isn't a "perfect" way of testing an antenna, it's close enough for gummint work, and the radio never "sees" a match worse than 2:1 during testing, regardless of how bad the antenna is.

Jim W4JED

On 1/27/19 7:04 AM, Paul wrote:
Hi Jim

Thanks for taking the time to answer my question.
Just so I don’t make any “newbie” incorrect assumptions here is what I have done following your suggestion.
Using a separate multimeter one probe on the negative 12v input.
2nd probe checked for continuity on all 3 points of Q6 with the radio powered off.
To clarify I am looking at the back of the board with the BNC connector top left.
I think I am right with my pin layout, pin1 top, 2 middle and 3 bottom?
Readings are
Pin1 0 ohms 
Pin2 .47 ohms
Pin3 open circuit

Thanks again Paul

From: <QRPLabs@groups.io> on behalf of James Daldry W4JED <jim@...>
Reply-To: "QRPLabs@groups.io" <QRPLabs@groups.io>
Date: Saturday, 26 January 2019 at 21:05
To: "QRPLabs@groups.io" <QRPLabs@groups.io>
Subject: Re: [QRPLabs] QCX 20 No output...New build

Hi, Paul

Q6 either is open, its collector is shorted to ground, or both. Check for zero ohms to ground from the collector. It should check open. If short, you either have a "whisker" short or one or more shorted FET's. If the collector reads shorted to ground pull the FET's and see if the short goes away. Once the short is cleared you'll need to replace Q6.

Jim W4JED

On 1/26/19 3:19 PM, paul.hadfield@... wrote:
This is the first kit of any kind I have built and everything has been a vertical learning curve.
On completion everything appears to work as expected just no power out.
I have checked continuity and re soldered all toroids, and they are fine.
Using the built in power meter I have checked for output at Q1,2 and 3 as suggested in the manual. No output at these points.
Having spent most of Saturday afternoon searching through posts to point me in the right direction I have been looking at the voltages with Q6.
Now I think something is wrong here but but not sure, and don't know where to begin correcting the situation if it is wrong.
Using the built in V meter I am seeing
Pin1 Emmiter , 11.45v key on or off
Pin2 Base, 11.1v key off and 7.46v keydown
Pin3 Collector 0v key on or off.

Any help would be appreciated as I would love to get it all working 100%

Paul


Re: Group storage

Andy G0FTD <punkbiscuit@...>
 

The price of success = group storage has run out.
Probably the first ever radio group to do so.
That'll teach young Hans to be so popular ;-)

Here's one idea, make an appeal for as many users as possible to delete their own posts / photo's in a mass act
of self moderation ?

If it's felt that something is unique or of good historical value then leave it, fair enough.

A group post and/or a group special message can be sent to all subscribers easily via the admin page to ask for this.

Once it appears to be down enough, Hans can get in and add his files into the files area.

I like using the group files area very much and it would be nice to still keep it as a one stop shop in addition to Hans's
own website.

73 de Andy