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installed QMX Rev 2 diode mod, now it is deaf

k9pz
 

I installed the diode and two days later started experiencing the audio issues others have been reporting.

The audio sweeps on 20m and 30m are erratic and 70db down. The sweeps on 80, 60, and 40m retain the correct shape but are about 50db down.

Power out is unstable on 20m via diagnostics, fluctuates between 3.5 and 4.5w.

I uninstalled the diode and nothing changed.

If i touch the windings on L401 audio improves on 40m.

I really screwed it up good this time!

Any tips would be greatly appreciated, i will see what else i can dig up.

Thanks

73 Brandon K9PZ
 

Check L503 for continuity. It may have been damaged.

JZ KJ4A

On Tue, Jan 16, 2024 at 3:46?PM k9pz <kd9okx@...> wrote:
I installed the diode and two days later started experiencing the audio issues others have been reporting.

The audio sweeps on 20m and 30m are erratic and 70db down. The sweeps on 80, 60, and 40m retain the correct shape but are about 50db down.

Power out is unstable on 20m via diagnostics, fluctuates between 3.5 and 4.5w.

I uninstalled the diode and nothing changed.

If i touch the windings on L401 audio improves on 40m.

I really screwed it up good this time!

Any tips would be greatly appreciated, i will see what else i can dig up.

Thanks

73 Brandon K9PZ

k9pz
 

No continuity. Thanks JZ. I'm new to this surface mount stuff. I can see it now. Will try to find a replacement. Hopefully thats all i broke.
 

Brandon, I recommend you install an SMD diode SOD323 style. 1N4148 or 1N4448. The leaded glass diode is difficult to install w/o breaking something. The leads are too strong. Good luck...JZ KJ4A


On Tue, Jan 16, 2024 at 4:19?PM k9pz <kd9okx@...> wrote:
No continuity. Thanks JZ. I'm new to this surface mount stuff. I can see it now. Will try to find a replacement. Hopefully thats all i broke.

k9pz
 

Thank you again.

It was very difficult to install, i think there was insufficient clearance with the case causing the damage.

I was able to goober enough solder on to L503 to regain continuity. 80,60,and 40m are all back in spec.

Tx is stable.

Audio and rf sweeps on 20 and 30m are still terrible.

73 K9PZ
 

Next, recheck the solder joints at L401. There may be some unremoved enamel remaining on the wires...JZ

On Tue, Jan 16, 2024 at 5:00?PM k9pz <kd9okx@...> wrote:
Thank you again.

It was very difficult to install, i think there was insufficient clearance with the case causing the damage.

I was able to goober enough solder on to L503 to regain continuity. 80,60,and 40m are all back in spec.

Tx is stable.

Audio and rf sweeps on 20 and 30m are still terrible.

73 K9PZ

k9pz
 

I did a recheck of L401. Everything seems good. QMX was A+ 100% beofrw i attempted the diode mod.

The issues on 20m and 30m are new, after diode mod attempt.

73 K9PZ
k9pz
 

Now my swr sweeps show flat lines at 10. No power out when tuning in diagnostics. Swr protection trips. Dummy load attached.

Yikes. I really broke something.
k9pz
 

And now it works, rf filter sweeps keep changing.
 

¿ªÔÆÌåÓý

Is it true that the diode mod is only needed on the Rev 2 boards?

Paul -- AI7JR

On 1/16/24 14:48, k9pz wrote:
And now it works, rf filter sweeps keep changing. 
-- 
Paul -- AI7JR
 

Are you in practice mode? If you turned on practice mode, there will be no signal generated, the RF sweep won't work properly.
--
73, de BD8BTE
op: Lun Yang
k9pz
 

It's true. Last line of Rev 2 mod page.
k9pz
 

I think i didnt have my dummy load attached all the way.
Still lots of issues. I need to replace C508 and L503 at minimum. Any recommendations?

I have 2 ceramic disk capacitors in parallel replacing C508 currently. L503 is damaged but seems to work? Maybe?

Tx is half power on all bands.

80,60, and 40m are ok but rx is down 10db or so from before botched mod. 20 and 30m are terribly out of spec.

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