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Hey everyone!
Bought this second hand, long story short its now mine and I'm trying to make the best of it. The nearest tech is about 6 hours away so I've been trying to figure this out myself and I've hit a wall, hopefully you guys can help me.
So first time I turned it on there was a massive wave crashing sound when going in and out of standby, as well as crackles (no playing because of this - immediately powered off). Opened up the chassis and saw C68 had been leaking, so I had changed all 8 electrolytic caps on the main board. Popped everything back in and further realized the tone controls don't work and neither does the post lead (or rhythm) - the pre control functions though (lead and rhythm). So to further explain the tone controls have zero function at all, the post lead/rhythm have an odd change, with very small change (say from 0-0.5) it'll actually drop volume and become very fizzy then another tiny adjustment up (0.6 to 10) and its a large jump but almost seems like if I plugged into the return jack, almost no gain and the post control doesn't change if its on 0.6 or 10.
I busted out the oscilloscope to trace the signal and there's a sign wave present at nearly every step in the schematic until we reach the wiper of the post controls (there is signal in the treble wiper and the tone controls do shape the wave). I have signal INTO the pot but nothing leaving the pot. So I figured perhaps something is wrong with the pots, had a spare 1MA that I know is good, no change, peavey pot showed fine when tested out of circuit. Have continuity to ground on the lug, checked the tone stack for continuity to ground.
I tested voltage on the pre amp tubes and they are as follows (following the tube layout per the schematic)
V1a 154/170
V1b 191/225
V2a 206/310
V2b 168/175
V5b 148/187
V5a 193/247
V3b 304 (v2+)
V3a 252/285
V4a 300/320
V4b 287310
Not even sure what to check or where to go.
Bought this second hand, long story short its now mine and I'm trying to make the best of it. The nearest tech is about 6 hours away so I've been trying to figure this out myself and I've hit a wall, hopefully you guys can help me.
So first time I turned it on there was a massive wave crashing sound when going in and out of standby, as well as crackles (no playing because of this - immediately powered off). Opened up the chassis and saw C68 had been leaking, so I had changed all 8 electrolytic caps on the main board. Popped everything back in and further realized the tone controls don't work and neither does the post lead (or rhythm) - the pre control functions though (lead and rhythm). So to further explain the tone controls have zero function at all, the post lead/rhythm have an odd change, with very small change (say from 0-0.5) it'll actually drop volume and become very fizzy then another tiny adjustment up (0.6 to 10) and its a large jump but almost seems like if I plugged into the return jack, almost no gain and the post control doesn't change if its on 0.6 or 10.
I busted out the oscilloscope to trace the signal and there's a sign wave present at nearly every step in the schematic until we reach the wiper of the post controls (there is signal in the treble wiper and the tone controls do shape the wave). I have signal INTO the pot but nothing leaving the pot. So I figured perhaps something is wrong with the pots, had a spare 1MA that I know is good, no change, peavey pot showed fine when tested out of circuit. Have continuity to ground on the lug, checked the tone stack for continuity to ground.
I tested voltage on the pre amp tubes and they are as follows (following the tube layout per the schematic)
V1a 154/170
V1b 191/225
V2a 206/310
V2b 168/175
V5b 148/187
V5a 193/247
V3b 304 (v2+)
V3a 252/285
V4a 300/320
V4b 287310
Not even sure what to check or where to go.
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