Anan 100 mic in audio fault?

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Stu
Posts: 17
Joined: Tue Feb 06, 2018 9:21 pm

Anan 100 mic in audio fault?

Postby Stu » Sun Mar 11, 2018 10:13 pm

Sorry for posting here again but i cant really see a group for hardware faults!

Hi All
I was using the Anan 2 days ago and suddenly my tx audio went very distorted and very low.
I tried cycling power etc but it was still distorted.
I then left it switched off for a short while and swapped microphones then tried again and all worked fine.

The same thing has happened this evening but this was with the 2nd microphone.
I immediately swapped mic's again but same problem.
So without switching off I enabled VAC and plugged the same mic into the PC and everything worked fine
Swapped back to the mic in socket and it was distorted again.
Swapped back to PC audio with VAC and it was fine again..

It looks like I have an intermittent fault on the front panel mic in audio path.
Possibly related to the Hermes board warming up after some use.

Looking at the schematic I would suspect U2 or an intermittent solder joint around U2 or the few passive components between the mic in socket and U2.

Would you say my conclusions are correct or could it be something else?
Thanks
Stu
Stu
Posts: 17
Joined: Tue Feb 06, 2018 9:21 pm

Re: Anan 100 mic in audio fault?

Postby Stu » Mon Mar 12, 2018 11:42 am

I've done some more testing and i'm sure this is heat related.
From cold the transmit audio is perfect via the mic in jack.
If I monitor transmit audio as the Anan warms up you can hear the audio starting to degrade and distort,.
Then within a few minutes there is virtually no audio at all.

While like this i have tried swapping mic's and no difference.

If I switch to VAC and plug the mic into the computer it works perfectly.

If i switch off and let the Anan cool down the mic in works fine again.

The more i think about it the more I'm convincing myself there is a problem with U2.
Stu
Posts: 17
Joined: Tue Feb 06, 2018 9:21 pm

Re: Anan 100 mic in audio fault?

Postby Stu » Mon Mar 12, 2018 2:54 pm

So further testing -

Removed front panel
Got the fault to happen again.
Put a 40mm fan appx over U2 (Its not too far from the front)
While the fan was running the audio started to recover.

So I'm pretty sure it is a heat related problem with U2, either the chip itself or a bad solder joint.

I guess next job will be to re-solder U2 pins and if that doesnt work replace U2
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w-u-2-o
Posts: 1304
Joined: Fri Mar 10, 2017 1:47 pm

Re: Anan 100 mic in audio fault?

Postby w-u-2-o » Mon Mar 12, 2018 3:30 pm

Post photos of the surgery ;)

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