Epiphone EA-15RVT treble control

[Amplodyte]

I am trying to repair/restore a 1964 Epiphone EA-15RVT Zephyr amp. It is exactly the same as a Gibson GA-25RVT Hawk using this schematic: https://drive.google.com/file/d/0Bxdn1sco9YrwNlo2VG43cVVZUjA/view
It appears to me that the treble pot on each channel is intended to have 93VDC on the wiper. Is this correct or is there a mistake on the schematic?
Thanks.

[Latole]

Most of the time, capacitor is before the pot.

With DC on pot, pot will be scratched , noisy.

[PRR]

> have 93VDC on the wiper.

Yes. Since DC has no path to go *through* the pot, scratch is unlikely. Pot shaft is well insulated, and metal shaft in metal bushing on grounded metal chassis should divert shock.

[Amplodyte]

Thank you for confirming my observation, I'll make sure that I have intact plastic knobs on the treble controls.
It seems like a fundamentally flawed design, is there a straightforward tweak that can be made to the circuit that removes the VDC from the pot? Or should I continue to attempt fixing the rest of the amp and see how the tonestack functions if I can the amp working?


 

[Latole]

> have 93VDC on the wiper.

Yes. Since DC has no path to go *through* the pot, scratch is unlikely. Pot shaft is well insulated, and metal shaft in metal bushing on grounded metal chassis should divert shock.

I won't trust that wiring. All tubes amps tone circuits I know use a capacitor before the pots

Why not to reverse cap and pot wiring ? Tone will work and no voltage at pot.

Fews modern pots with plastic shaft I used, don't last long.

[PRR]

I don't understand why you think this is shocking. Half a million tube home radios did this.

It does not need plastic knob, a plastic shaft is no safer than a metal shaft in a grounded metal bushing.

Yes, you can reverse the Pot and C if you like.

[Latole]

Safety was not same 60 years ago.