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CJ 1.4: Power tubes are working but drivers not ! Help please.

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Hello,

I am the owner of a Conrad Johnson Premier Four amplifier. Power tubes (EL34) are working (light, hot) but drivers tubes (5751, 6CG7) are not working (no light, cold). No sound in speakers ( no little noise like it works). Schematics I have on 1.4: only 3. Someone have an idea ?
Thank you very much !
 
Hi,

Well firstly check the heaters are working on the driver tubes. get the pinout from the net (TDSL duncan amps is a good place) and set your DMM to AC and measure accross the heater pins.
If you read 6.3Vish (im guessing these tubes are 6.3v?) then it may be that the filament has expired.
Pull them out of the amp when its off and measure resistance accross the same heater terminals of the tube, it should be near short circuit, if its open circuit then theyre fried and youll need a new set of driver tubes.

Thats a starting point, there may be a reason the heaters are gone so see what happens here before you replace the tubes.

--One more thing be very careful when going inside the amplifier! make sure you use one hand when possible and dont brush any parts when probing.
 
Thank you very much for these informations. I have another set of drivers tubes. I try with them but with no result. The thing I don't completely understand is why the four tubes are not working. Power problem ? Schematics diagrams I have download are not complete. Perhaps a bad solder...
 
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