I just finished aleph1.2 clones and am getting nearly no sound at all from it. I measure the same values when I measure left and right channel, see schematics.
Everything is as the schematics say except the MPSA 18 are replaced with BC 550 (yes I do know about the reversed pins, so they are turned 180 degrees)
Her are some facts/measures:
- amp built as per schematics (KK-PCB)
- hear very low signal trough amps
- The mosfets are matched within 0,015V, but will not heat up
- I measure 69 Volts over mosfets (no voltage drop at all), but no volts over R40-51
- Powersupply with testload measured 58V
- BC 550 used (not MPSA 18), otherwise original parts
- Q1, Q2 and Q3 are hot (but not to hot)
any help would be MUCH appreciated,
cheers,
Ole Bjørn
Everything is as the schematics say except the MPSA 18 are replaced with BC 550 (yes I do know about the reversed pins, so they are turned 180 degrees)
Her are some facts/measures:
- amp built as per schematics (KK-PCB)
- hear very low signal trough amps
- The mosfets are matched within 0,015V, but will not heat up
- I measure 69 Volts over mosfets (no voltage drop at all), but no volts over R40-51
- Powersupply with testload measured 58V
- BC 550 used (not MPSA 18), otherwise original parts
- Q1, Q2 and Q3 are hot (but not to hot)
any help would be MUCH appreciated,
cheers,
Ole Bjørn
Attachments
for start - instead R11 put 100R resistor in series with 100R pot ,then try to set pot to have nearer to 4V across R14 , chasing 0,5V across source resistors of output mosfets
to my eyes - you don't have enough current through input LTP (Q1,Q2) , so not enough current through R14 , so not enough voltage across it to open enough lower bank of output mosfets ;
one thing you didn't measured - output DC voltage ; I can bet that you have there near +55V
to my eyes - you don't have enough current through input LTP (Q1,Q2) , so not enough current through R14 , so not enough voltage across it to open enough lower bank of output mosfets ;
one thing you didn't measured - output DC voltage ; I can bet that you have there near +55V
Zen Mod said:
I can bet that you have there near +55V
Thats normal you're pita, sorry pithia of BaC afterall...
Naaah, just sincerely admirative how you can do ferndiagnose ...
You know what I mean...
I am always fascinated how some issues (when then solved) can bring so much understanding in a given matter...
Manu
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.