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Mesa Prodigy
http://forum.grailtone.com/viewtopic.php?f=14&t=70357
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Author:  markstuk [ Sun Aug 30, 2015 6:10 am ]
Post subject:  Mesa Prodigy

Hi

Got hold of my Prodigy four:88 a few weeks ago - my first all valve amp in 25 odd years (last was a Hiwatt DR201)

Playing it through either a Barefaced Super 12T or a Tecamp L810..

I'm liking it a lot, but it seems to get louder throughout a gig - such that I have to keep turning it down.. Is this normal?

Also does anyone know where I can get the FC.PROD footcontroller in the UK or Europe? Noone seems to have any stock..

Regards



Mark

Author:  soundguruman [ Sun Aug 28, 2016 9:39 am ]
Post subject:  Re: Mesa Prodigy

First, it's not an all valve amp - it's 1/2 solid state. The preamp EQ and driver are all transistors...combined with tubes.
We call this a "Hybrid" amplifier.

Second - volume fluctuation
I suspect the 2 MOSFET transistors in the phase inverter driver stage need replacing. OR clean / replace the VOICE switch.

Also, try swapping the preamp tubes, one at a time with a new 12AX7, and retest the amp each time.
Plug a guitar cable between effects send and effects return jacks...and re-test. The jacks have internal switches which can corrode and fail. This will cause fluctuations or it may stop working completely.
Whether or not you use the effects loop - the audio goes thru the effects jack switches. If the switch oxidizes the volume can cut in and out.

Plugging a guitar cable between send and return bypasses the jack switches. This is a good test to see if those switch contacts are failing.

No, you do not work on this amp yourself.
It requires EXPERT skill and professional soldering equipment.

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