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QDX Troubleshooting Help Needed

 

Hello,
I just put together the QDX yesterday. When I did some testing and upgraded the firmware to 1.05, I get 5 watts out on 80, 5 watts out on 60, nothing notable on 40 but I did make several QSO's on 40, about 1.5 watts on 30 and not showing anything on 20. From looking at the schematic, obviously the PA is working. I did continuity tests at the cathodes of the pin diodes to verify LPF connections. The 40 LPF was near 1 ohm and the other two were .2 ohms. After reheating the toroid connections, 40 is now showing .2 ohms, but still no power out. Its strange that I was able to work TX, SC, VA and FL on 40 but showing no power out. I guess QRP does work LOL?

Thanks for any advice in advance,
Gary, NY9R
 

Gary,?
Have you tried checking the Terminal Application sweeps? If so how do the bands look? The RF Filter sweep will be the most telling.?

A nice matrix of cathode voltages has been posted here and I can't find it at the moment. I'm going to try and recreate it here:

? ? ? ? ? ? D1? ? ?D2? ? ?D3? ? ?D4? ? ?D5? ? ?D6
80m? ? ? L? ? ? ? H? ? ? ?H? ? ? ?L? ? ? ?H? ? ? ?H? ? ? ?
40m? ? ? H? ? ? ?L? ? ? ? H? ? ? ?H? ? ? ?L? ? ? ?H
30m? ? ? H? ? ? ?H? ? ? ?L? ? ? ? H? ? ? ?H? ? ? ?L
20m? ? ? H? ? ? ?H? ? ? ?L? ? ? ? H? ? ? ?H? ? ? ?L

L or Low is ~0V
H or High is around the voltage you built your kit for.

These are from my QDX testing and I'm almost sure they agree with what's been posted.

The measurements are made while in the terminal program in the RF Filter Sweep test.

You may need to reflow the diode connections.

Hope it helps!

--Al
WD4AH
 

Al,
Thanks for the reply. I will check this. I ran the sweep on all bands, but really didn't know what I was looking for, but all waveforms were very similar in shape except for 20 and it had a different pattern.?
I will be out of town over the weekend,? so it will be a few days before I can do further testing.?

Thanks again,?
Gary. NY9R?
 

Look for 2 of the 4 BS 170s blown and also a failed act08.
Just worked on one that did the exact same thing.

NOTE: replace all 4 BS170s for safety.

If you scoping it look at the output of the act08 for each pair
of the? BS170s, one will have very different looking drive
if any at all.


Allison
------------------
Post online only, please no email.
 

Al,
I finally got some time to do some troubleshooting on the QDX. From the chart you posted, all of the logic was correct. I scoped waveforms into and out of the LPF's and everything looked normal....even waveforms on the bands with issues. I decided to try another watt meter and I was showing output on the other meter. It appears that when I bypassed a 3 position coax switch, all bands were putting out fine. 80,60,40, 30,20 = 5 watts. I have no idea why going through the coax switch was allowing 80 and 60 to show 5 watts and the other bands nearly nothing, but hey, its working!
I had some issues with the coax switch before, but I thought I had solved the issues.....might be time to toss it.
Anyway, thanks again for you help and hope to work you on the air someday!
Gary, NY9R
 

Gary,
Good to hear you are up and running! Thanks for the follow-up info!!
73,

--Al
 

¿ªÔÆÌåÓý

Gary, et al,

Coax switches are just switches, somewhat like a light switch. ?With RF they are a little more fiddly and I have found they get dirty, corrode, and just plain fail. ?I take my coax switches apart about once a year and clean them and make sure they are making good contact. ?Same with the roller inductor in my antenna tuner. ?They all need maintenance. RF isn¡¯t just connectivity like a battery and a light bulb. ?It needs more care. ?And sometimes just to see I take the antenna switch out of the circuit¡­.. and voila, things sometimes work better. ?If the switch is working then I check the pieces of coax used to connect to the switch. They fail too. ?This is all part of what the experience of 62 years has taught me. ?Just because switches and pieces of coax and coax connectors are all plugged into each other doesn¡¯t mean at all that they are doing what we think they are, especially with RF. ?

Dave K8WPE?

David J. Wilcox¡¯s iPad

On Oct 11, 2022, at 5:31 PM, Gary Stout <pwrbasc@...> wrote:

?Al,
I finally got some time to do some troubleshooting on the QDX. From the chart you posted, all of the logic was correct. I scoped waveforms into and out of the LPF's and everything looked normal....even waveforms on the bands with issues. I decided to try another watt meter and I was showing output on the other meter. It appears that when I bypassed a 3 position coax switch, all bands were putting out fine. 80,60,40, 30,20 = 5 watts. I have no idea why going through the coax switch was allowing 80 and 60 to show 5 watts and the other bands nearly nothing, but hey, its working!
I had some issues with the coax switch before, but I thought I had solved the issues.....might be time to toss it.
Anyway, thanks again for you help and hope to work you on the air someday!
Gary, NY9R

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