Microphonic Mesa Tremoverb

JD50

so my amp is making an awful whine..... it's been like this since I bought a couple months ago but only just got round to playing the pre amp valve swap game until today.

put a new valve in V1 a Brand new premium selected and have been sawaping out the other 5 position one by one but no dice.

The whining noise is kind of tolerable in the clean setting and as I go through vintage gain / blues/ modern high gain it gets worse. 

Makes no no difference whether reverb is on or off.

The whine is briefly magnified when I switch the amp off.

I am taking it in for service in September after my hols but if any of you good folk have any suggestion meanwhile?

Thanks

ICBM

Is it affected by the controls at all? If so, which ones?

Does it still do it if the rectifier is set to Diode (solid state)?

JD50

Been through all controls and switched between bold/spongy and no difference.

Tap tested all the valves incl power/rectifier and no unexpected noise. 

ICBM

Curious… none of the controls affecting it would seem to indicate a power stage issue, but if it gets worse as you go through the gain modes then it sounds more like the preamp.

I wonder if it's something like a filtering failure in the LT power supply which is then being amplified through the LDR switches? Random guess!

Definitely one for the experienced tech if it's not a valve, anyway - these are not easy amps to troubleshoot, as you'll probably know if you've ever looked inside it. Unfortunately I don't have mine any more, or I could try testing some things.

JD50

ICBM said:

Curious… none of the controls affecting it would seem to indicate a power stage issue, but if it gets worse as you go through the gain modes then it sounds more like the preamp.

I wonder if it's something like a filtering failure in the LT power supply which is then being amplified through the LDR switches? Random guess!

Definitely one for the experienced tech if it's not a valve, anyway - these are not easy amps to troubleshoot, as you'll probably know if you've ever looked inside it. Unfortunately I don't have mine any more, or I could try testing some things.

No worries thanks for your help. It's going in for a service in a month so hopefully an easy/not too expensive fix.
Am taking it to John Kelly who has a good rep and decades of experience so he should be able to find the fault.

Thanks again!

DJH83004

Would be interested to hear what your tech finds on this one, the ones I have repaired in the past have all had problems with the LDRs, (which are effectively optocouplers), causing channel fade and similar symptoms. But as stated by IC, they are difficult to work on, so I hope it is a cheap / easy fix, but wouldn't Bank on it