orange OR15

[Valvehead]

Weird issue... The amp is working after re-tensioning the PI socket. It would cut out moving the PI tube . But strangely , the Treble pot is now acting as a " master volume " control and the mid and bass pots have zero effect on the signal. The MV and Gain pots work normal . treble on 0 and the amp has no signal. Anyone seen this issue ?? The amp has never been apart. Possibly a bad Treble pot? I can loosen the nut and move it and signal doesnt cut out so I think the solder joints are ok at the pot. I tried clean/ lube on the treble pot .

Orange OR15 SCH 115V-230V.pdf Orange OR15 SCH 115V-230V.pdf

[Jon Snell]

Bad connection or pin 1 connected to ground with a splash of solder .... who knows.
Socket issues are normally caused by incorrectly inserted valves. Check the receptacles are still receiving the pins in the centre, not down the side.
Treble issue ...
Not a lot to check here. R17 O/C?

[g1]

Does pin1 of mid pot have good ground connection? What is resistance of each pin of treble pot to ground?

[Valvehead]

Bad connection or pin 1 connected to ground with a splash of solder .... who knows.
Socket issues are normally caused by incorrectly inserted valves. Check the receptacles are still receiving the pins in the centre, not down the side.
Treble issue ...
Not a lot to check here. R17 O/C?

I corrected the PI socket. Its good and so are the rest of the tube sockets. Im going to pull the pcb and inspect the bottom

[Valvehead]

Does pin1 of mid pot have good ground connection? What is resistance of each pin of treble pot to ground?

Mid pot has good ground.

treble pot has 83 ohm / 84 ohm -leg 1 (turning pot)

84 ohm -190k (turning the pot) leg 2

190k- 245k ( turning pot )

[x-pro]

John Snell: "Not much to check here R17 O/C"
Have you checked?

[Valvehead]

John Snell: "Not much to check here R17 O/C"
Have you checked?

47k in / out of circuit .



Do those resistance measurements 100% rule out the treble pot itself ?

[x-pro]

If this resistor does not have a connection on the printed circuit board in the circuit (break, misconnection), then there will be no tone controls, and the treble control will partially become a level control.

[Valvehead]

If this resistor does not have a connection on the printed circuit board in the circuit (break, misconnection), then there will be no tone controls, and the treble control will partially become a level control.

ok. To fully check that area i will have to pull the pcb...no way to access the caps on top

[g1]

treble pot has 83 ohm / 84 ohm -leg 1 (turning pot)

If this is from treble pot to ground, that is definitely a problem. Minimum from treble leg 1 to ground should be 25K.

[Valvehead]

If this is from treble pot to ground, that is definitely a problem. Minimum from treble leg 1 to ground should be 25K.

ok...im pulling pcb tonight . Got a 250k pot ordered in case .

[Jon Snell]

Don't throw spares at it, fault find!
Measure the resistance between pin 1 of RV4 and ground, from your fault description, that is where your issue is; Short to ground.

[Valvehead]

Thanks guys--it was the Treble pot. works great now