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Picked one of these up as a project and started going through it last night.
Replaced the can cap, disconnected and tested all other caps and replaced what was out out of spec.
Cleaned switches and pots.
Removed the old oil [which was clean in appearance but a little stinky] and applied enough new, proper oil to a level which I believe to be correct.
The unit already generally worked as a preamp but was a little noisy. Now it plays through very nicely and quietly and sounds nice as it gets turned up. The bass, treble and distortion switches all work fine.
The two level trim pots on the back of the preamp chassis work fine. The rotation of the motor/disc is barely audible so that tells me the can is at least “live”. The inside of the can is very clean and I’ve adjusted the heads to be 90° with the closest edge of the disc.
I’ve read the effect switches with an ohmeter and they are all working properly. The pots have drifted some but are generally working.
Haven’t found any broken wires, reading from end to end for continuity.
What should I be looking for next?
Click the thumbnail for the schematic and voltages at the tube sockets. Do the grid and cathode voltages look reasonable for the 2nd tube?
Replaced the can cap, disconnected and tested all other caps and replaced what was out out of spec.
Cleaned switches and pots.
Removed the old oil [which was clean in appearance but a little stinky] and applied enough new, proper oil to a level which I believe to be correct.
The unit already generally worked as a preamp but was a little noisy. Now it plays through very nicely and quietly and sounds nice as it gets turned up. The bass, treble and distortion switches all work fine.
The two level trim pots on the back of the preamp chassis work fine. The rotation of the motor/disc is barely audible so that tells me the can is at least “live”. The inside of the can is very clean and I’ve adjusted the heads to be 90° with the closest edge of the disc.
I’ve read the effect switches with an ohmeter and they are all working properly. The pots have drifted some but are generally working.
Haven’t found any broken wires, reading from end to end for continuity.
What should I be looking for next?
Click the thumbnail for the schematic and voltages at the tube sockets. Do the grid and cathode voltages look reasonable for the 2nd tube?