Hello all
This orange has had me puzzled .
Came in for sounding bad. Found on the EL84 been gassed. Tested all the pre amp tubes and replaced all the EL84
Sounded good. On Bias test i found that one test point was 10.40v TP6 but TP7 is at 8.20v
So i tried 2 other new sets of new tubes all the same
So tested with 2 x New sets of TAD EL84 and 1 x New set of Marshall selected JJ EL84 ( all New and Matched )
All the same issue.. Checked over the board for soldering or cracks on the pcb. Tube bases look fine
Orange_TH-30 Twin Channel Amplifier.pdf
So i changed both 220uf and the 120R, didn't expect there to be any change and there wasn't
Ive had the amp on and working all sounds ok, But there is a problem there
Taken some voltages reads of bias and Plate
Full power with 4 tubes
V6 10.4v - 313v
V7 8.3v -314v
V8 10.4v - 309v
V9 8.3v - 309v
Full power with 2 tubes
V6 21v - 330v
V7 8.7v -330v
V8 21v - 324v
V9 8.3v - 324v
I have checked the 2-4 tube switch that's ok. all outputs are working, with a brief test all sounded ok
Im a little baffled to whats going on
many thanks
This orange has had me puzzled .
Came in for sounding bad. Found on the EL84 been gassed. Tested all the pre amp tubes and replaced all the EL84
Sounded good. On Bias test i found that one test point was 10.40v TP6 but TP7 is at 8.20v
So i tried 2 other new sets of new tubes all the same
So tested with 2 x New sets of TAD EL84 and 1 x New set of Marshall selected JJ EL84 ( all New and Matched )
All the same issue.. Checked over the board for soldering or cracks on the pcb. Tube bases look fine
Orange_TH-30 Twin Channel Amplifier.pdf
So i changed both 220uf and the 120R, didn't expect there to be any change and there wasn't
Ive had the amp on and working all sounds ok, But there is a problem there
Taken some voltages reads of bias and Plate
Full power with 4 tubes
V6 10.4v - 313v
V7 8.3v -314v
V8 10.4v - 309v
V9 8.3v - 309v
Full power with 2 tubes
V6 21v - 330v
V7 8.7v -330v
V8 21v - 324v
V9 8.3v - 324v
I have checked the 2-4 tube switch that's ok. all outputs are working, with a brief test all sounded ok
Im a little baffled to whats going on
many thanks
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