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Substitute for PCC86 in Model 90-T Anniversary

CZ4A

CZ4A

Active Member
I bought a Fisher Model 90-T Anniversary tuner as a recap project. It also needs a couple of new tubes. One of the tube sockets is marked on the chassis as "V50067." I found a service manual that says the V50067 is a PCC86. I think it is the FM RF amplification tube.

The PCC86 is pretty much unobtainium. What would be the best way to substitute for it? Can I use a different frame grid tube like a 7DJ8 or 7ES8? Or should I lower the filament voltage on that pin to 6.3V and run a 6GM8 (ECC86)?
 
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Wow,now that is a really strange place to see this tube type! They are running the plate voltage ( 160 & 85,in cascode configuration) far higher than the Design Center spec of 30 volts,and they also seem to be blowing away the heater-cathode max (30 volts) also. Very strange that they would choose this type,go to the trouble of incorporating a filament tap just for this one tube,and then run it at ''conventional'' voltage levels.

This tube (at it's specified operating voltages) has a much lower transconductance than the DJ8 or AQ8. Maybe at the levels it was operating at in this circuit,they may be comparable. Again,what a weird design choice!
 
actually the v50067 is a pcc88 or a 7dj8 run on a 6v heater circuit. it's a 6dj8 with a 7v heater which would help it last longer. you can sub a 6dj8 but it won't last as long, but should perform samilarly. put a 6dj8 in my 80-R and it runs fine
 
larryderouin said:
actually the v50067 is a pcc88 or a 7dj8 run on a 6v heater circuit. it's a 6dj8 with a 7v heater which would help it last longer. you can sub a 6dj8 but it won't last as long, but should perform samilarly. put a 6dj8 in my 80-R and it runs fine
Click to expand...

My mistake! In my defense, it's a bit hard to make out the last digit of "PCC88" in the schematic and a Google search does have vacuum-tube related results for PCC86. That tube looks to be very obscure, though. That would also explain the high operating voltages Arts mentioned - I don't think a 6GM8-type would last very long!
 
Ok,I also got burned on this one.I read ''PCC86'' on the schematic as well; it really does look like a 6:confused: On a positive note,this should make your project a little easier.
 
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