VHT Special 6 out of volume

[wole]

Sorry for delay - I've been away.


The idea of keeping the probe in one place was to check the continuity across the whole chain as well as the resistances. The total resistance you measure should be the sum of the resistance in the chain between the two probes.

No matter since you measured R22 as shorted. The boost switch shorts R22 in normal so you are in low gain mode. If the foot switch is connected, remove it and check the operation of the boost switch. Does it work the same on both amps?

Yes it works the same in both amps.. I can measure nothing in both when in normal mode (switch off) and 63K ohm in the good working amp and 64K in the bad working amp when in boost mode (switch on). Also I've checked that the loss of volume is noticeable with both a 16ohm speaker and a 8ohm speaker, so I don't think it's a problem of the output... what do you think at this point?

[nickb]

Yes it works the same in both amps.. I can measure nothing in both when in normal mode (switch off) and 63K ohm in the good working amp and 64K in the bad working amp when in boost mode (switch on). Also I've checked that the loss of volume is noticeable with both a 16ohm speaker and a 8ohm speaker, so I don't think it's a problem of the output... what do you think at this point?

We tested the output power roughly earlier on, we know that's OK.

All gains, ACV and DCV look good. I think you are saying the boost switch works properly. I would say it's working perfectly 'cept it isn't..

All I can suggest now is to get both amps side by side, set the controls fully clockwise and repeat the ACV measurements, note them and look for big differences. Make sure you have the same level of input signal at V101a pin 2 in both amps and same speaker load impedance before you start.

Note ACV at V101a-2, V101a-3, Wiper of Volume control, V101b-7, V101b-6, V102-5, V102-3