Topics

QCX+ alignment SNAFU


Lloyd K3ESE
 

the situation thus far: I completed construction, and began alignment. When I got to 8.7 "HIT SELECT," and did, I could hear a tone in the headphones, but very slight; not loud. Adjusting C1 allowed me to peak the volume of sound heard - it never got really loud, but it clearly gets louder at a certain point - but the display never changed at all, while I was adjusting C1. 

This was where I stopped. Help!!!


Mike Besemer - WM4B
 

Check the soldering on T1 with an ohmmeter.  Make sure you touch it to the pads or the solder and not the wire.  This will also help you verify that you’ve got all the leads in the correct spot.

 

Mike

WM4B

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Lloyd K3ESE
Sent: Sunday, October 18, 2020 12:24 PM
To: QRPLabs@groups.io
Subject: [QRPLabs] QCX+ alignment SNAFU

 

the situation thus far: I completed construction, and began alignment. When I got to 8.7 "HIT SELECT," and did, I could hear a tone in the headphones, but very slight; not loud. Adjusting C1 allowed me to peak the volume of sound heard - it never got really loud, but it clearly gets louder at a certain point - but the display never changed at all, while I was adjusting C1. 

This was where I stopped. Help!!!


Lloyd K3ESE
 

ok; just repeated this. good continuity; everything seems right with T1.


Ronald Taylor
 

Hi Lloyd. It sounds from the symptoms you gave, like the problem is in the area from T1 to the outputs of IC6A and IC7A. If you haven't already done so, follow the great troubleshooting guidelines here: http://qrp-labs.com/qcx/qcxtrouble.html and see if you can locate the issue. Pay particular attention to the DC bias measurements on T1 and ICs 5,6 and 7. 

Good luck ... Ron

On Sun, Oct 18, 2020 at 9:48 AM Lloyd K3ESE <llachow@...> wrote:
ok; just repeated this. good continuity; everything seems right with T1.


Lloyd K3ESE
 

sadly, I have no o-scope, nor training to use one. Does this mean I'm 3/3 for failed QCX attempts??


Mike Besemer - WM4B
 

Can you post some good pictures of the solder side of the board?  And a couple of the component side too.

 

Mike

WM4B

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Lloyd K3ESE
Sent: Sunday, October 18, 2020 1:59 PM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] QCX+ alignment SNAFU

 

sadly, I have no o-scope, nor training to use one. Does this mean I'm 3/3 for failed QCX attempts??


Lloyd K3ESE
 

for some reason, I can't attach any pics here


Ronald Taylor
 

Lloyd, I’d you have a DVM, read the voltages at pins 1,2,3,5,6&7 of IC 5,6&7. Using you external DVM you should see about 3.5 volts at all these points. If you use the built in DVM they will be different. Refer to the values on the chart for that. This will help rule out some of the possible issues. 

Ron

On Sun, Oct 18, 2020 at 11:28 Lloyd K3ESE <llachow@...> wrote:
for some reason, I can't attach any pics here










Lloyd K3ESE
 

Yikes.

with a 13.8V supply

IC5
1  4.9V
2  .434V
3  10.8mV
5  111.4mV
6  .721V
7  1.31V

If I power up with no key plugged in, pin 1 is at around 12.5V, and all the other readings are also off.

IC6
1  1.40V
2  1.38V
3  1.36V
5  1.31V
6  1.33V
7  1.36V

IC7
1  4.77V
2  4.77V
3  4.77V
5  4.76V
6  4.76V
7  4.76V

something is terribly wrong - but what? My best guess is I have to redo T1. What size wire? Does anyone have an extra 6' they're willing to part with?


N3MNT
 

Can you post some good close up photos


Lloyd K3ESE
 

apparently not...I tried multiple times, earlier. mobile and desktop.


Ronald Taylor
 

Lloyd, before you do that, please look at page 18 of the instructions and check voltages at points 5,6,7 &8 on T1. Also make sure your R1 and R2 are properly inserted and soldered and of the correct value. You should see 2.5 volts on points 5,6,7&8 of T1. 

Ron

On Sun, Oct 18, 2020 at 1:02 PM N3MNT <bob@...> wrote:
Can you post some good close up photos


Lloyd K3ESE
 

Ron,

R1 and R2 are correct...but the readings on T1 aren't. 1-4 are all 0V, as they should be.
But

5  186mV
6  248mV
7  250mV
8  272mV


Ronald Taylor
 

OK. please check voltages on both sides of R1 and R2. One side of R2 should be 5 volts and the other should be 2.5 V. One side of R1 should be 2.5 V and the other side should be zero v (ground).

Ron

On Sun, Oct 18, 2020 at 1:25 PM Lloyd K3ESE <llachow@...> wrote:
Ron,

R1 and R2 are correct...but the readings on T1 aren't. 1-4 are all 0V, as they should be.
But

5  186mV
6  248mV
7  250mV
8  272mV


Lloyd K3ESE
 

Ron,

R1
top 5.4V
bot  249mV

R2
top 0V
bot 248mV


Ronald Taylor
 

Lloyd, it looks like something is wrong with R1. It appears to be open, either not soldered or a bad component. Please test that resistor and see what's going on with it... Ron


On Sun, Oct 18, 2020 at 1:38 PM Lloyd K3ESE <llachow@...> wrote:
Ron,

R1
top 5.4V
bot  249mV

R2
top 0V
bot 248mV


Ronald Taylor
 

Disregard the last note. I'm re-reading what you indicated... Standby ... Ron


On Sun, Oct 18, 2020 at 1:47 PM Ron Taylor <wa7gil@...> wrote:
Lloyd, it looks like something is wrong with R1. It appears to be open, either not soldered or a bad component. Please test that resistor and see what's going on with it... Ron

On Sun, Oct 18, 2020 at 1:38 PM Lloyd K3ESE <llachow@...> wrote:
Ron,

R1
top 5.4V
bot  249mV

R2
top 0V
bot 248mV


Ronald Taylor
 

Lloyd, sorry for the delay. I was confused for a moment because R1 on the schematic is actually R2 on the board. Please now, with the rig power removed, use your ohm meter and check resistance from T1 points 5,6,7&8 to ground. You should see about 5K ohms at all 4 points.... Ron


On Sun, Oct 18, 2020 at 1:50 PM Ronald Taylor via groups.io <wa7gil=gmail.com@groups.io> wrote:
Disregard the last note. I'm re-reading what you indicated... Standby ... Ron

On Sun, Oct 18, 2020 at 1:47 PM Ron Taylor <wa7gil@...> wrote:
Lloyd, it looks like something is wrong with R1. It appears to be open, either not soldered or a bad component. Please test that resistor and see what's going on with it... Ron

On Sun, Oct 18, 2020 at 1:38 PM Lloyd K3ESE <llachow@...> wrote:
Ron,

R1
top 5.4V
bot  249mV

R2
top 0V
bot 248mV


Lloyd K3ESE
 

Those four points are all 5.58K ohms.


Ronald Taylor
 

Well, I'm stumped. Can't see any shorts and resistors appear OK. Forgive me for asking, but is your DVM doing some kind of auto-ranging incorrectly? The 250 mV you see is exactly 10% of what you should be seeing. I don't know why that would be happening, but it may be leading us down the wrong path if it is. If you have another meter, it might be worth the time to try that before we proceed... Thanks .. Ron


On Sun, Oct 18, 2020 at 2:13 PM Lloyd K3ESE <llachow@...> wrote:
Those four points are all 5.58K ohms.