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Build help and troubleshooting => MP573 Microphone preamplifier => Topic started by: reezmaz on April 25, 2023, 04:49:49 PM

Title: MP573 failed setup guide check after running for 2 years
Post by: reezmaz on April 25, 2023, 04:49:49 PM

Hello!

I built my MP573 2 years or so ago, got it up and running sounding great. However, this week it has started having big issues. The signal is very quiet, distorts quickly, and only has the frequencies of an old telephone. 

I took the unit out of my rack, and found that it now fails the first check on the 'MP573-setup-guide', indicating that there is a short circuit. I get a reading between OV and V+, but no reading before V- and OV - I don't know what to do next, is anyone able to please advise?

Many thanks in advance,
Rhys

Title: Re: MP573 failed setup guide check after running for 2 years
Post by: JPK on April 26, 2023, 03:06:48 PM

I get a reading between OV and V+
What resistance value do you get? If it is in kohms, then not an issue.
Check the supply voltage between TP2 and V+ : 24V.

Title: Re: MP573 failed setup guide check after running for 2 years
Post by: reezmaz on April 27, 2023, 12:46:33 PM

Thanks for this - 

The reading between 0V and V+ flashes only for couple seconds before increasing into a non reading, so I guess that's all good.

Just checked the supply voltage between TP2 and V+ and found it is indeed 24V

Any other thoughts?

Thanks again

Title: Re: MP573 failed setup guide check after running for 2 years
Post by: reezmaz on April 28, 2023, 10:38:05 AM

P.S. worth noting I also completed the 'usual suspects' and DC voltage checks across the board listed on 'In case your MP573 doesn't work as expected (https://www.soundskulptor.com/forum/index.php?topic=5.msg5#msg5)'  and got all the correct readings

Title: Re: MP573 failed setup guide check after running for 2 years
Post by: JPK on April 29, 2023, 10:11:09 AM

Now you need to follow the signal do find out where it stops.
I have added some of the values you should get in the post (https://www.soundskulptor.com/forum/index.php?topic=5.msg5#msg5).

Title: Re: MP573 failed setup guide check after running for 2 years
Post by: reezmaz on May 01, 2023, 11:52:50 AM

With a sine signal sitting around 0.5VAC between pins 2/3 of the input xlr, I'm getting no reading at all from pin 7 on the input transformer. TP2 is giving me a tiny reading of 0.06VAC, and the output transformer yellow wire is reading at 48V

Title: Re: MP573 failed setup guide check after running for 2 years
Post by: JPK on May 03, 2023, 08:28:44 AM

the output transformer yellow wire is reading at 48V
??? AC or DC? You may have an issue with your meter. Check the battery.

Check the solder joints on both transformers.
Do you get the same issue from the DI input?

Title: Re: MP573 failed setup guide check after running for 2 years
Post by: reezmaz on May 03, 2023, 11:48:11 PM

48 VAC - my meter appears to be working fine and giving me accurate readings on everything else

Same issue on the DI yes

I have however started getting issues on other slots in my API rack, and so starting to worry that the this is where the fault lies. Does this sound to you like something that could be a more general power supply issue? It's an API 500 6B.. I fear I will be unable to fully diagnose the issue myself at this stage

Title: Re: MP573 failed setup guide check after running for 2 years
Post by: JPK on May 04, 2023, 09:39:41 AM

Does this sound to you like something that could be a more general power supply issue?
If the DC voltage on V+ (24V against TP2) is correct, then it is not a PSU issue.
If you want us to check it, please contact me here (https://www.soundskulptor.com/en/content/6-contact).