No Input to VC2

[Keith S]

Hello Ted and all. I have a VC2 that I use regularly in my studio for vocal tracking. In a session last night, it suddenly stopped working. The unit still powers up but will not pass audio through the mic input and there is no action on the meter. If I plug the mic into the line input, I do get a low level signal as one would expect.

This is with a dynamic mic so I know it’s not a phantom power issue. The mic and cable check out OK on another preamp. Are there any known issues that would cause such a failure?

Thank you

Keith

[Ted Fletcher]

Hi Keith, this is an odd one….. is there a front panel jack on this model? I can’t remember. If there is then that is where the problem is. If not, drop me an email.

[Keith S]

Hi Ted. There is no front panel jack. I noticed that the phantom power started to get noisy (sounded like 60 cycle hum) about a week before it stopped working. I thought at first the 48vdc failed but dynamic mics do not work either. When it failed, there was no pop, bang, buzz or any other noise, it just stopped passing audio and there is no action on the meter.

On Saturday, I dropped it off with a local tech along with your hand-written schematic

[Ted Fletcher]

Hmm, sounds like a failure of the input capacitors on the input stage, it’s likely that replacing them will fix it.

But let’s see what your tech says.

Ted

[Keith S]

The tech got it working. Says he thinks it was some oxidation on the TRS insert which he cleaned. I never use the insert so I can see how the contact could be broken from oxidation over time. Wouldn’t this also affect the line-in as well?

[Ted Fletcher]

Yes, this will probably affect line in as well….. it’s a common fault, but reasonably easily fixed.

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