Fisher X-101st schematic

Well it's running and sounding very sweet.

My X-1000 schematic doesn't list any voltages so I'd like to ask for opinions of where there at.

AC after single CL80 - 117 VAC

Plates - 375 volts

Screens - 328 volts before the 100 ohm resistors and 326 volts after.

Cathode voltage - 18 volts

Cathode current - 33 ma

AC heaters - 6.2 VAC

DC heaters - 9.2 VDC (V1 & V6)

Looks like the EL84M matched quad are dissipating 12.37 Watts each.

Please provide feedback and clue as to why the DC filament voltage is so low. I don't have a TT but want to be able to use one.

R92 is 10K and I replaced it with a 1% carbon film. R93 is 6.8k and checks good and is carbon comp.

20220117_202735.jpg
 
using this schematic right?

1961 Fisher Executive V and VI Console Service Manual Page (fisherconsoles.com)

Voltages and current look reasonable on the output stage.

The V1 and V6 heater voltages are just what they are because it powers off the cathode. Split that 18v in half and thats what you get per-tube. Not really an easy way to bump that without either beating the output tubes up pretty badly or making things a lot more complicated than they need to be. If those tubes are healthy it should be OK even at those voltages. Weaker tubes won't be happy though.
 
Thanks gadget!

I had the voltage page and forgot about it untill you brought it to my attention.

I'm happy with the voltages, cathode current and dissipation. I'm also very pleased with the sound. When the time comes to hook up a TT, I'll experiment with different tubes in V1 & V6 positions.

Thanks to everyone who contributed to the resurrection of this fine little amp!
 
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I would probably stick with old production just so you have a known quantity on the heater. I have no idea if modern tube heaters are as tightly controlled as old ones, and changing things there will not do the output tubes any favors.
 
When I recieved the amp, the only old production tubes were in V1 & V6. Everything else was GT (Groove Tubes) including the Rectifier.

I'm running vintage Mullard & Telefunken ECC83's, Sovtek EL84M matched quad from Jim McShane and a vintage Mullard GZ34.

On another note:
I'm guessing there is no easy was to adjust the phase inverter pots with a meter like the 400, 500, 800, Etc.? I would at least like to clean/lubricate them. I thought about disconnecting them and noting the resistance readings and reconnecting them.
How close could they possibly be after replacing all those components?

Thoughts?
 
yeah can adjust it the same basic way. Measure the value of R72, then measure from pin 3 of V3 to ground. Adjust the pot until those numbers match. On the other channel its R75 and V8.
 
R72 & R75 are both 100K. R72 is reading 104K while R75 is reading 108K. The pots pin 3 is approximately 111K. I'll change them both and make adjustments accordingly.

Thanks gadget!
 
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