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Post subject: Re: '64 Twin Reverb voltage question
Posted: Sun Mar 16, 2014 3:24 pm
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Aspiring Musician
Aspiring Musician

Joined: Sun Oct 27, 2013 7:11 am
Posts: 318
BMW2002Ti wrote:
upnorth wrote:
I did some research and it's been explained that PI grids can't be measured properly with DMM because of bootstrapping? (long tailed pair). There's supposed to be another way to measure it, across the resistors maybe, I need to do more research.


Which parameter can't be read at the PI grids? Fender has the pertinent voltages on their schematic. +98VDC (grid to ground point) and +100VDC (cathodes). With no signal input, you should have very little (like mV) of VAC (really should be zero VAC).


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I was measuring from the PI 12AT7 grids to ground, which loads the circuit with a DMM. I needed to measure grid to cathode which gives me -1.98v's, which is close to what it should be. I've got all the voltages really close now so the problem has to be a tranny.

Thanks for the help guys, I really appreciate it.


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