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I've got a Crate Vintage Club 50 that's suffering from a lack of power. Here's what I've done to trouble shoot so far:
The voltages are off by 80-90V, but they're off in the power amp stage as well, which leads me to believe that that's not the issue here. Anyone have any ideas to give me a shove in the right direction?
Crate Vintage Club 50 - Schematic.pdf
- Checked continuity across the legs of the effects loop jack with no plug. Everything checked out, I went ahead and gave a good spray down with some contact cleaner just to be sure.
- Plugged straight into the effects loop. The sound is full and powerful when I plug in here...leads me to believe the issue is in the preamp stage.
- Checked out values on the opto-couplers. I'd read that these tend to go bad. When the respective channels were on I was reading from 600 to 1K on the "resistor" side, which is right where they should be based on my calculations.
- Measured B+ voltages. This is where I'm seeing a pretty big discrepancy from the testpoints labeled on the schematic (which I've attached).
Test Point - Chart - Measured
TP18 - 381V - 461V
TP19 - 391V - 471V
TP6 - 308V - 397V
TP5 - 290V - 379V
The voltages are off by 80-90V, but they're off in the power amp stage as well, which leads me to believe that that's not the issue here. Anyone have any ideas to give me a shove in the right direction?
Crate Vintage Club 50 - Schematic.pdf