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The gain controls make a really loud scratchy sound (not a bad pot) and don't control the gain. All three channels are really weak in the gain department. I've tracked the problem down to the first triode of the second preamp tube, my voltages are way off.
On the plate I get 200v, cathode 1.8v, grid 33mv,
Should be 277 on the plate, 2 on the cathode, nothing on the grid...
This stage isnt capacitor coupled, and has a couple of transistors going across the grid resistor. I honestly don't know crap about transistors, but I'm suspecting one of these (j175) might be bad. I have checked the plate resistor, it is ok and I get the proper voltage (400v) on the other side of it, and the cathode caps and resistor are fine as well. I have a schematic if you guys need it, but have any of you seen a problem like this before?
I also noticed in the schematic they have a note:
"1. Mute circuit J-FET'S. There are three of these in the signal chain. See that
the gate voltage is momentarily dipping low at the instant of switching to Mute
signal path.
2. Look for any amount of DC leakage onto V2A grid from the J-FET that is
bypassing the 475K series resistor"
The 475k resistor is connected to the grid of v2a... On the schematic it says either j176 or j175, I can't tell which, but I'm thinking it's a 176 since the datasheet picture of those looks like it.
On the plate I get 200v, cathode 1.8v, grid 33mv,
Should be 277 on the plate, 2 on the cathode, nothing on the grid...
This stage isnt capacitor coupled, and has a couple of transistors going across the grid resistor. I honestly don't know crap about transistors, but I'm suspecting one of these (j175) might be bad. I have checked the plate resistor, it is ok and I get the proper voltage (400v) on the other side of it, and the cathode caps and resistor are fine as well. I have a schematic if you guys need it, but have any of you seen a problem like this before?
I also noticed in the schematic they have a note:
"1. Mute circuit J-FET'S. There are three of these in the signal chain. See that
the gate voltage is momentarily dipping low at the instant of switching to Mute
signal path.
2. Look for any amount of DC leakage onto V2A grid from the J-FET that is
bypassing the 475K series resistor"
The 475k resistor is connected to the grid of v2a... On the schematic it says either j176 or j175, I can't tell which, but I'm thinking it's a 176 since the datasheet picture of those looks like it.
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