Topics

No output QCX 40 output drains show 1.6 watts in receive


George Korper
 

Hi,
 I replaced the three BS 170's  in the amp and using
internal wattmeter show no output and 1.6 watts on the drains during receive..
I replaced Q5 and no difference. Not sure which voltages to check.
I realize there should be no watts on the drain in receive as I checked my QCX 20.
Thanks,
George


Alan G4ZFQ
 

 I replaced the three BS 170's  in the amp and using
internal wattmeter show no output
George,

and 1.6 watts on the drains during receive..
The wattmeter only gives sensible results on the output when going into a dummy load. All other checks should be with the voltmeter.

I replaced Q5 and no difference.
Check Q6 voltages. Your "1.6 watts" seems to show that is faulty.
Also check IC3 voltages.
>Not sure which voltages to check.
As in the manual.

Do you know what happened to cause this? Any observations?

73 Alan G4ZFQ
I realize there should be no watts on the drain in receive as I checked my QCX 20.
Thanks,


George Korper
 

Thank you Alan,
Ok so far. First I have a QRL dummy load and it is plugged in. 
I went ahead and replaced Q6. No change. 
I will try to get voltages on IC3, but I didn't see the voltages listed in the list, are they somewhere else?
May I remove the LCD do get to to IC3 and still take the voltages?
The QCX was running fine, but my straight key which was plugged my have
come on while the OLG was connected and running WSPR. I looked at the key and a tiny, tiny speck
of some material was caught in the minute  gap and it took a piece of paper to remove it. If it can happen it will happen I guess.
That is one supposition. In my collection of cables I pulled the key when I realized what was happening and the plug hit something
on the open end of the QCX and some sparks flew. After I cleaned it up, thinking all was lost I checked the QCX and I did see output,
when I realized I had high SWR for some reason, and it turned out what ever happened back in the rat's nest the MFJ SDR switch
was no longer working. The QCX seemed fine, at least in my nervous condition but now I was rattled and decided I should to wait until
morning. I was wrong, now there was no output. The bottom line is at sometime the QCX was operating with the WSPR running and the key shorted, As for the MFG which has an RF sensor that may have just been bad for a while and causing the high SWR. I  noticed that the high SWR caused the QCX to go up very high in power. So as for the cause it is murky!
I have read Han's manual over and over and I do wish I had just settled for seeing that it is better off running at 2 to 3 watts out on my wattmeter
which is 5 watts into a dummy load using the internal rf probe. I would have saved the groups time and a lot of anguish adjusting toroids, etc.

I'd change Q4 but first I will await your reply on IC3 and the removal of the LCD.

.


On Tue, Dec 10, 2019 at 10:56 AM Alan G4ZFQ <alan4alan@...> wrote:
>   I replaced the three BS 170's  in the amp and using
> internal wattmeter show no output

George,

>and 1.6 watts on the drains during
> receive..

The wattmeter only gives sensible results on the output when going into
a dummy load. All other checks should be with the voltmeter.

> I replaced Q5 and no difference.

Check Q6 voltages.  Your "1.6 watts" seems to show that is faulty.
Also check IC3 voltages.
  >Not sure which voltages to check.
As in the manual.

Do you know what happened to cause this? Any observations?

73 Alan G4ZFQ
> I realize there should be no watts on the drain in receive as I checked
> my QCX 20.
> Thanks,
>




Alan G4ZFQ
 

I went ahead and replaced Q6. No change.
George,

Replacing things blindly may not work. It is not unusual for several components to blow in the PA, replacing one component may blow it again. Voltage readings are important. Also check voltages after you remove a suspect but before you renew it.

I will try to get voltages on IC3, but I didn't see the voltages listed in the list, are they somewhere else?
http://www.qrp-labs.com/qcx/qcxtrouble.html#transmit
May I remove the LCD do get to to IC3 and still take the voltages?
Yes

The QCX was running fine.......
Quite a story:-) Settle down do it slowly. Measure voltages, remove anything suspect, measure voltages.. Report here.

73 Alan G4ZFQ


George Korper
 

IC3 Voltages LCD unplugged:
some values rounded off.
1) 5
2) 5
3) 5
4) .02
5) .01
6) 5
7) 0
8) 5
9) 0
10) 0
 11) 0
12) 5
13) 5
14) 5

On Tue, Dec 10, 2019 at 4:31 PM Alan G4ZFQ <alan4alan@...> wrote:
> I went ahead and replaced Q6. No change.

George,

Replacing things blindly may not work. It is not unusual for several
components to blow in the PA, replacing one component may blow it again.
Voltage readings are important. Also check voltages after you remove a
suspect but before you renew it.

> I will try to get voltages on IC3, but I didn't see the voltages listed
> in the list, are they somewhere else?

http://www.qrp-labs.com/qcx/qcxtrouble.html#transmit
> May I remove the LCD do get to to IC3 and still take the voltages?
Yes

> The QCX was running fine.......

Quite a story:-) Settle down do it slowly. Measure voltages, remove
anything suspect, measure voltages.. Report here.

73 Alan G4ZFQ




George Korper
 

I sent you receive voltages. Thanks for the link, I forgot to reread the trouble shooting section.
There was no change in voltages in transmit, so
I can see the 12 Volts is not on the pins in transmit.
In transmit nothing on the IC3 changes.


On Tue, Dec 10, 2019 at 4:59 PM George Korper via Groups.Io <georgekorper=gmail.com@groups.io> wrote:
IC3 Voltages LCD unplugged:
some values rounded off.
1) 5
2) 5
3) 5
4) .02
5) .01
6) 5
7) 0
8) 5
9) 0
10) 0
 11) 0
12) 5
13) 5
14) 5

On Tue, Dec 10, 2019 at 4:31 PM Alan G4ZFQ <alan4alan@...> wrote:
> I went ahead and replaced Q6. No change.

George,

Replacing things blindly may not work. It is not unusual for several
components to blow in the PA, replacing one component may blow it again.
Voltage readings are important. Also check voltages after you remove a
suspect but before you renew it.

> I will try to get voltages on IC3, but I didn't see the voltages listed
> in the list, are they somewhere else?

http://www.qrp-labs.com/qcx/qcxtrouble.html#transmit
> May I remove the LCD do get to to IC3 and still take the voltages?
Yes

> The QCX was running fine.......

Quite a story:-) Settle down do it slowly. Measure voltages, remove
anything suspect, measure voltages.. Report here.

73 Alan G4ZFQ




George Korper
 

Alan,  I checked pin 3 again and it is still showing 5 volts. which I see shouldn't be 5 but zero.
The transmit voltages are not changed but the same as receive.


On Tue, Dec 10, 2019 at 5:30 PM George Korper via Groups.Io <georgekorper=gmail.com@groups.io> wrote:
I sent you receive voltages. Thanks for the link, I forgot to reread the trouble shooting section.
There was no change in voltages in transmit, so
I can see the 12 Volts is not on the pins in transmit.
In transmit nothing on the IC3 changes.


On Tue, Dec 10, 2019 at 4:59 PM George Korper via Groups.Io <georgekorper=gmail.com@groups.io> wrote:
IC3 Voltages LCD unplugged:
some values rounded off.
1) 5
2) 5
3) 5
4) .02
5) .01
6) 5
7) 0
8) 5
9) 0
10) 0
 11) 0
12) 5
13) 5
14) 5

On Tue, Dec 10, 2019 at 4:31 PM Alan G4ZFQ <alan4alan@...> wrote:
> I went ahead and replaced Q6. No change.

George,

Replacing things blindly may not work. It is not unusual for several
components to blow in the PA, replacing one component may blow it again.
Voltage readings are important. Also check voltages after you remove a
suspect but before you renew it.

> I will try to get voltages on IC3, but I didn't see the voltages listed
> in the list, are they somewhere else?

http://www.qrp-labs.com/qcx/qcxtrouble.html#transmit
> May I remove the LCD do get to to IC3 and still take the voltages?
Yes

> The QCX was running fine.......

Quite a story:-) Settle down do it slowly. Measure voltages, remove
anything suspect, measure voltages.. Report here.

73 Alan G4ZFQ




George Korper
 

I understand with the voltage on the gate of the output transistor, it is consistent  with the output on the drain.
but is the IC3 bad? My electronics education is not deep enough to come up with it ( hi hi) Everything was working fine so at least I can rule out
bad soldering, but replacing the output transistors was stupid. I NOW HAVE LEARNED WHY YOU INSIST ON VOLTAGE MEASUREMENT FIRST. Thanks for being a good Elmer. 


On Tue, Dec 10, 2019 at 10:37 PM George Korper via Groups.Io <georgekorper=gmail.com@groups.io> wrote:
Alan,  I checked pin 3 again and it is still showing 5 volts. which I see shouldn't be 5 but zero.
The transmit voltages are not changed but the same as receive.


On Tue, Dec 10, 2019 at 5:30 PM George Korper via Groups.Io <georgekorper=gmail.com@groups.io> wrote:
I sent you receive voltages. Thanks for the link, I forgot to reread the trouble shooting section.
There was no change in voltages in transmit, so
I can see the 12 Volts is not on the pins in transmit.
In transmit nothing on the IC3 changes.


On Tue, Dec 10, 2019 at 4:59 PM George Korper via Groups.Io <georgekorper=gmail.com@groups.io> wrote:
IC3 Voltages LCD unplugged:
some values rounded off.
1) 5
2) 5
3) 5
4) .02
5) .01
6) 5
7) 0
8) 5
9) 0
10) 0
 11) 0
12) 5
13) 5
14) 5

On Tue, Dec 10, 2019 at 4:31 PM Alan G4ZFQ <alan4alan@...> wrote:
> I went ahead and replaced Q6. No change.

George,

Replacing things blindly may not work. It is not unusual for several
components to blow in the PA, replacing one component may blow it again.
Voltage readings are important. Also check voltages after you remove a
suspect but before you renew it.

> I will try to get voltages on IC3, but I didn't see the voltages listed
> in the list, are they somewhere else?

http://www.qrp-labs.com/qcx/qcxtrouble.html#transmit
> May I remove the LCD do get to to IC3 and still take the voltages?
Yes

> The QCX was running fine.......

Quite a story:-) Settle down do it slowly. Measure voltages, remove
anything suspect, measure voltages.. Report here.

73 Alan G4ZFQ




Charles W. Powell
 

Start tracing your audio chain. You can use a screwdriver to “inject” hum into the op amp if you are careful not to short pins.   I have had several QCX units I have repaired that had a fault near IC8.  It’s worth checking.  You can figure out where you lose signal this way and separate an audio fault from something upstream.   You said you don’t HEAR the alignment tone, but did you get a meter peak when you adjusted C1?

73,

Charles

On Dec 10, 2019, at 6:58 PM, George Korper <georgekorper@...> wrote:

I understand with the voltage on the gate of the output transistor, it is consistent  with the output on the drain.
but is the IC3 bad? My electronics education is not deep enough to come up with it ( hi hi) Everything was working fine so at least I can rule out
bad soldering, but replacing the output transistors was stupid. I NOW HAVE LEARNED WHY YOU INSIST ON VOLTAGE MEASUREMENT FIRST. Thanks for being a good Elmer. 


On Tue, Dec 10, 2019 at 10:37 PM George Korper via Groups.Io <georgekorper=gmail.com@groups.io> wrote:
Alan,  I checked pin 3 again and it is still showing 5 volts. which I see shouldn't be 5 but zero.
The transmit voltages are not changed but the same as receive.


On Tue, Dec 10, 2019 at 5:30 PM George Korper via Groups.Io <georgekorper=gmail.com@groups.io> wrote:
I sent you receive voltages. Thanks for the link, I forgot to reread the trouble shooting section.
There was no change in voltages in transmit, so
I can see the 12 Volts is not on the pins in transmit.
In transmit nothing on the IC3 changes.


On Tue, Dec 10, 2019 at 4:59 PM George Korper via Groups.Io <georgekorper=gmail.com@groups.io> wrote:
IC3 Voltages LCD unplugged:
some values rounded off.
1) 5
2) 5
3) 5
4) .02
5) .01
6) 5
7) 0
8) 5
9) 0
10) 0
 11) 0
12) 5
13) 5
14) 5

On Tue, Dec 10, 2019 at 4:31 PM Alan G4ZFQ <alan4alan@...> wrote:
> I went ahead and replaced Q6. No change.

George,

Replacing things blindly may not work. It is not unusual for several
components to blow in the PA, replacing one component may blow it again.
Voltage readings are important. Also check voltages after you remove a
suspect but before you renew it.

> I will try to get voltages on IC3, but I didn't see the voltages listed
> in the list, are they somewhere else?

http://www.qrp-labs.com/qcx/qcxtrouble.html#transmit
> May I remove the LCD do get to to IC3 and still take the voltages?
Yes

> The QCX was running fine.......

Quite a story:-) Settle down do it slowly. Measure voltages, remove
anything suspect, measure voltages.. Report here.

73 Alan G4ZFQ











George Korper
 

Hi Charles,
My problem is no output receive is okay. 
Thanks, 
George. 

On Tue, Dec 10, 2019, 7:34 PM Charles W. Powell via Groups.Io <doctorcwp=yahoo.com@groups.io> wrote:
Start tracing your audio chain. You can use a screwdriver to “inject” hum into the op amp if you are careful not to short pins.   I have had several QCX units I have repaired that had a fault near IC8.  It’s worth checking.  You can figure out where you lose signal this way and separate an audio fault from something upstream.   You said you don’t HEAR the alignment tone, but did you get a meter peak when you adjusted C1?

73,

Charles

On Dec 10, 2019, at 6:58 PM, George Korper <georgekorper@...> wrote:

I understand with the voltage on the gate of the output transistor, it is consistent  with the output on the drain.
but is the IC3 bad? My electronics education is not deep enough to come up with it ( hi hi) Everything was working fine so at least I can rule out
bad soldering, but replacing the output transistors was stupid. I NOW HAVE LEARNED WHY YOU INSIST ON VOLTAGE MEASUREMENT FIRST. Thanks for being a good Elmer. 


On Tue, Dec 10, 2019 at 10:37 PM George Korper via Groups.Io <georgekorper=gmail.com@groups.io> wrote:
Alan,  I checked pin 3 again and it is still showing 5 volts. which I see shouldn't be 5 but zero.
The transmit voltages are not changed but the same as receive.


On Tue, Dec 10, 2019 at 5:30 PM George Korper via Groups.Io <georgekorper=gmail.com@groups.io> wrote:
I sent you receive voltages. Thanks for the link, I forgot to reread the trouble shooting section.
There was no change in voltages in transmit, so
I can see the 12 Volts is not on the pins in transmit.
In transmit nothing on the IC3 changes.


On Tue, Dec 10, 2019 at 4:59 PM George Korper via Groups.Io <georgekorper=gmail.com@groups.io> wrote:
IC3 Voltages LCD unplugged:
some values rounded off.
1) 5
2) 5
3) 5
4) .02
5) .01
6) 5
7) 0
8) 5
9) 0
10) 0
 11) 0
12) 5
13) 5
14) 5

On Tue, Dec 10, 2019 at 4:31 PM Alan G4ZFQ <alan4alan@...> wrote:
> I went ahead and replaced Q6. No change.

George,

Replacing things blindly may not work. It is not unusual for several
components to blow in the PA, replacing one component may blow it again.
Voltage readings are important. Also check voltages after you remove a
suspect but before you renew it.

> I will try to get voltages on IC3, but I didn't see the voltages listed
> in the list, are they somewhere else?

http://www.qrp-labs.com/qcx/qcxtrouble.html#transmit
> May I remove the LCD do get to to IC3 and still take the voltages?
Yes

> The QCX was running fine.......

Quite a story:-) Settle down do it slowly. Measure voltages, remove
anything suspect, measure voltages.. Report here.

73 Alan G4ZFQ











Charles W. Powell
 

Alright.  I hadn’t been following the thread all that well.

73,

Charles - NK8O

On Dec 10, 2019, at 7:49 PM, George Korper <georgekorper@...> wrote:

Hi Charles,
My problem is no output receive is okay. 
Thanks, 
George. 

On Tue, Dec 10, 2019, 7:34 PM Charles W. Powell via Groups.Io <doctorcwp=yahoo.com@groups.io> wrote:
Start tracing your audio chain. You can use a screwdriver to “inject” hum into the op amp if you are careful not to short pins.   I have had several QCX units I have repaired that had a fault near IC8.  It’s worth checking.  You can figure out where you lose signal this way and separate an audio fault from something upstream.   You said you don’t HEAR the alignment tone, but did you get a meter peak when you adjusted C1?

73,

Charles

On Dec 10, 2019, at 6:58 PM, George Korper <georgekorper@...> wrote:

I understand with the voltage on the gate of the output transistor, it is consistent  with the output on the drain.
but is the IC3 bad? My electronics education is not deep enough to come up with it ( hi hi) Everything was working fine so at least I can rule out
bad soldering, but replacing the output transistors was stupid. I NOW HAVE LEARNED WHY YOU INSIST ON VOLTAGE MEASUREMENT FIRST. Thanks for being a good Elmer. 


On Tue, Dec 10, 2019 at 10:37 PM George Korper via Groups.Io <georgekorper=gmail.com@groups.io> wrote:
Alan,  I checked pin 3 again and it is still showing 5 volts. which I see shouldn't be 5 but zero.
The transmit voltages are not changed but the same as receive.


On Tue, Dec 10, 2019 at 5:30 PM George Korper via Groups.Io <georgekorper=gmail.com@groups.io> wrote:
I sent you receive voltages. Thanks for the link, I forgot to reread the trouble shooting section.
There was no change in voltages in transmit, so
I can see the 12 Volts is not on the pins in transmit.
In transmit nothing on the IC3 changes.


On Tue, Dec 10, 2019 at 4:59 PM George Korper via Groups.Io <georgekorper=gmail.com@groups.io> wrote:
IC3 Voltages LCD unplugged:
some values rounded off.
1) 5
2) 5
3) 5
4) .02
5) .01
6) 5
7) 0
8) 5
9) 0
10) 0
 11) 0
12) 5
13) 5
14) 5

On Tue, Dec 10, 2019 at 4:31 PM Alan G4ZFQ <alan4alan@...> wrote:
> I went ahead and replaced Q6. No change.

George,

Replacing things blindly may not work. It is not unusual for several 
components to blow in the PA, replacing one component may blow it again. 
Voltage readings are important. Also check voltages after you remove a 
suspect but before you renew it.

> I will try to get voltages on IC3, but I didn't see the voltages listed 
> in the list, are they somewhere else?

http://www.qrp-labs.com/qcx/qcxtrouble.html#transmit
> May I remove the LCD do get to to IC3 and still take the voltages?
Yes

> The QCX was running fine.......

Quite a story:-) Settle down do it slowly. Measure voltages, remove 
anything suspect, measure voltages.. Report here.

73 Alan G4ZFQ














Alan G4ZFQ
 

In transmit nothing on the IC3 changes.
George,

IC3 looks as if it has failed. If pins 1,2 are high then pin 1 should be low.
What are the voltages on Q1,2,3?

Also it looks as if IC1 is not sending a TX signal to IC3 and that Clk2 is not turned on for TX.
Is it going into TX mode? Does IC1 pin 3 go low when the "Key" switch is pressed?

73 Alan G4ZFQ


IC3 Voltages LCD unplugged:
some values rounded off.
1) 5
2) 5
3) 5
4) .02
5) .01
6) 5
7) 0
8) 5
9) 0
10) 0
 11) 0
12) 5
13) 5
14) 5


George Korper
 

Alan,
The drain and gate on Q1 Q2 and Q3 are 5 v and the source 0. CLK 1 goes from 1.7 on receive to zero on transmit.
Not sure of pinout on IC1 directly. 
George






On Wed, Dec 11, 2019, 3:54 AM Alan G4ZFQ <alan4alan@...> wrote:
> In transmit nothing on the IC3 changes.

George,

IC3 looks as if it has failed. If pins 1,2 are high then pin 1 should be
low.
What are the voltages on Q1,2,3?

Also it looks as if IC1 is not sending a TX signal to IC3 and that Clk2
is not turned on for TX.
Is it going into TX mode? Does IC1 pin 3 go low when the "Key" switch is
pressed?

73 Alan G4ZFQ


>     IC3 Voltages LCD unplugged:
>     some values rounded off.
>     1) 5
>     2) 5
>     3) 5
>     4) .02
>     5) .01
>     6) 5
>     7) 0
>     8) 5
>     9) 0
>     10) 0
>       11) 0
>     12) 5
>     13) 5
>     14) 5
>





George Korper
 

D!1 at output is 3.3 and IC1 pin 1 is  1.8 assuming that is top right pin.


On Wed, Dec 11, 2019 at 12:33 PM George Korper via Groups.Io <georgekorper=gmail.com@groups.io> wrote:
Alan,
The drain and gate on Q1 Q2 and Q3 are 5 v and the source 0. CLK 1 goes from 1.7 on receive to zero on transmit.
Not sure of pinout on IC1 directly. 
George






On Wed, Dec 11, 2019, 3:54 AM Alan G4ZFQ <alan4alan@...> wrote:
> In transmit nothing on the IC3 changes.

George,

IC3 looks as if it has failed. If pins 1,2 are high then pin 1 should be
low.
What are the voltages on Q1,2,3?

Also it looks as if IC1 is not sending a TX signal to IC3 and that Clk2
is not turned on for TX.
Is it going into TX mode? Does IC1 pin 3 go low when the "Key" switch is
pressed?

73 Alan G4ZFQ


>     IC3 Voltages LCD unplugged:
>     some values rounded off.
>     1) 5
>     2) 5
>     3) 5
>     4) .02
>     5) .01
>     6) 5
>     7) 0
>     8) 5
>     9) 0
>     10) 0
>       11) 0
>     12) 5
>     13) 5
>     14) 5
>





Alan G4ZFQ
 

CLK 1
goes from 1.7 on receive to zero on transmit.
George,

That's enough to tell it is going to TX mode.
You need to remove IC3 and test the voltages on it's pin 4 and pin 12 pads, RX and TX modes.

IC3 can be removed by carefully cutting each leg then removing each leg separately.

73 Alan G4ZFQ
IC3 looks as if it has failed. If pins 1,2 are high then pin 1
should be
low.
What are the voltages on Q1,2,3?
Also it looks as if IC1 is not sending a TX signal to IC3 and
that Clk2
is not turned on for TX.
Is it going into TX mode? Does IC1 pin 3 go low when the "Key"
switch is
pressed?


George Korper
 

Hi Alan,
Game over as I don't have a replacement for IC3.
I did order another 40 QCX and i will take all the experience
and now with skills at voltage checking, do better next time.
Again thanks and best 73's
George

On Wed, Dec 11, 2019 at 2:53 PM Alan G4ZFQ <alan4alan@...> wrote:
> CLK 1
>     goes from 1.7 on receive to zero on transmit.

George,

That's enough to tell it is going to TX mode.
You need to remove IC3 and test the voltages on it's pin 4 and pin 12
pads, RX and TX modes.

IC3 can be removed by carefully cutting each leg then removing each leg
separately.

73 Alan G4ZFQ
>
>         IC3 looks as if it has failed. If pins 1,2 are high then pin 1
>         should be
>         low.
>         What are the voltages on Q1,2,3?
>
>         Also it looks as if IC1 is not sending a TX signal to IC3 and
>         that Clk2
>         is not turned on for TX.
>         Is it going into TX mode? Does IC1 pin 3 go low when the "Key"
>         switch is
>         pressed?
>
>         




Alan G4ZFQ
 

Game over as I don't have a replacement for IC3.
George,

OK, although they should be easy to source. But I am thinking that further faults may be found if the voltages are checked.
Maybe look at again sometime, you learn more about how something works when it does not work!

73 Alan G4ZFQ


George Korper
 

Yes, I will take another look this morning, but I see a small hole in the top of IC1 under magnification.
So I will send it over tp AZ for a second opinion. When the next QCX gets here I have decided to assemble in
several better ways for my manner of operation, including better solder, sockets for iIC's and an enclosure.
Gracias Amigo. Oh, and a new respect for voltage measurement. 

On Thu, Dec 12, 2019 at 6:48 AM Alan G4ZFQ <alan4alan@...> wrote:
> Game over as I don't have a replacement for IC3.

George,

OK, although they should be easy to source. But I am thinking that
further faults may be found if the voltages are checked.
Maybe look at again sometime, you learn more about how something works
when it does not work!

73 Alan G4ZFQ