Trouble shooting help!

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13. October 2025, 17:30:14

Diskussions- und Newsboard des DARC-Ortsverbandes I40 | allgemeine Kategorie | mcHF Projekt Deutsch / English (here you can discuss everything related to mcHF) (Moderators: DF8OE, DL1PQ) | Topic: Trouble shooting help!

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WD8BXS
alter Hase

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Trouble shooting help!
« on: 07. October 2025, 12:52:32 »

Hello everyone, I hope everyone is OK, it's been awhile, hi hi .. I haven't worked on the Mchf much lately, so I am rusty.
I have one here with no transmit. I started checking a C7 - C8 on the UI board, but I am getting nothing there/. I have replaced the Codec chip but to no avail.. Any ideas where to look next??

TNX Chuck, WD8BXS, VY 73

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Thanks,
De WD8BXS vy 73

DF8OE
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Stellvertr. OVV I40, Jugend / Nachwuchsreferent

Re:Trouble shooting help!
« Reply #1 on: 08. October 2025, 04:46:52 »

Hi Chuck,

nice to read from you again and see you are quite active with mcHF

You have to control the complete signal path and see where something is lost. While transmitting (test tone is appreciated) you must see signals from TX codec output to quadrature mixer (both I and Q). Second signal pair is I/Q mixing from oscillator arriving at mixer. If all 4 (!) are present it can be missing TX-DC-signal or mixer is completely dead. Use a scope for analyzing signals. Good luck - please provide result if you have fixed it!

vy 73
Andreas

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WD8BXS
alter Hase

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Re:Trouble shooting help!
« Reply #2 on: 08. October 2025, 15:58:12 »

Hello Andreas!! Nice hearing from you!

I am still active although the eyes aren't as good as they were, hi hi

It looks like this mystery just got better, I went back to the bench and it was working fine, then 5 minutes later it quit again.

Now the hunt for an intermittent problem ensues!!

Thanks, Chuck

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De WD8BXS vy 73

DF8OE
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Re:Trouble shooting help!
« Reply #3 on: 09. October 2025, 04:57:29 »

This are the problems which cost much time to fix. I know them very good, we are "best friends"

. Devices are working fine when they are opened on my table, but if I close the cases 10 minutes later they get broken again...

Good luck! I apply some "test points" in the middle of the row and so I can decide if the issue exists before or after my testpoint, when issue pops up. Then I put new testpoint in the middle of the remaining part where the issue is and so I got a decreasing amount of possible causes... Takes time, but works.

vy 73
Andreas

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