Hi all,
I have a hifonics alpha 3000.1D that goes directly into protect upon connection of remote power. Nothing on the board looks bad to the naked eye. All of the FETs measure OK.
This amp uses the TL494 for the power supply. I've checked all the SOT23-3 transistors near it and they all "measure" OK. Of course they could've failed in an open state.
I'll check the voltages going into the 2 opamps of the TL494 tomorrow. Does anyone have a schematic for this guy?
Attached some pictures of the amp.
I have a hifonics alpha 3000.1D that goes directly into protect upon connection of remote power. Nothing on the board looks bad to the naked eye. All of the FETs measure OK.
This amp uses the TL494 for the power supply. I've checked all the SOT23-3 transistors near it and they all "measure" OK. Of course they could've failed in an open state.
I'll check the voltages going into the 2 opamps of the TL494 tomorrow. Does anyone have a schematic for this guy?
Attached some pictures of the amp.
Attachments
I don't have a diagram.
What's the part number on the IC U108(?) adjacent to the output driver IC?
What's the part number on the IC U108(?) adjacent to the output driver IC?
Copy and paste the following list and fill in the blanks. If there is no blank space after the colon, add one between the colon and the numbers you enter. It makes it much easier to read.
DCV on all terminals of the TL494.
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:
DCV on all terminals of the TL494.
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:
Pin 1: 2.65V
Pin 2: 4.47V
Pin 3: 4.64V
Pin 4: 4.17V
Pin 5: 1.46V
Pin 6: 3.70V
Pin 7: 0V
Pin 8: 14.03V
Pin 9: 0V
Pin 10: 0V
Pin 11: 14.03V
Pin 12: 13.28V
Pin 13: 5.03V
Pin 14: 5.03V
Pin 15: 5.03V
Pin 16: 10.09V
Pin 2: 4.47V
Pin 3: 4.64V
Pin 4: 4.17V
Pin 5: 1.46V
Pin 6: 3.70V
Pin 7: 0V
Pin 8: 14.03V
Pin 9: 0V
Pin 10: 0V
Pin 11: 14.03V
Pin 12: 13.28V
Pin 13: 5.03V
Pin 14: 5.03V
Pin 15: 5.03V
Pin 16: 10.09V
IUf you lift Q604, does the amp power up?
Be careful, this should disable part of the protection circuit.
Be careful, this should disable part of the protection circuit.
It powers with Q604 removed!
I see rail-rail oscillation before the LC filter as well. But there doesn't seem to be any modulation when I input audio. I can trace that tomorrow but what would cause it to be in protect like that?
I see rail-rail oscillation before the LC filter as well. But there doesn't seem to be any modulation when I input audio. I can trace that tomorrow but what would cause it to be in protect like that?
Do you have supply voltage across the PS pins of U108?
IS there a burned component just behind the RCA jacks?
IS there a burned component just behind the RCA jacks?
This amp has some similarities with yours (different/missing output stage).
https://www.diyaudio.com/community/threads/ir2010-burnt-traces.402358/post-7477196
https://www.diyaudio.com/community/threads/ir2010-burnt-traces.402358/post-7477196
I removed the filter after the RCAs and jumpered them. The amp plays music fine, I can drive it into clipping and the waveform looks clean all the way up.
It seems that the issue is now isolated to the protection circuit on the TL494.
It seems that the issue is now isolated to the protection circuit on the TL494.
Reconnect the protection circuit to see if it still has a problem now that you jumped the inductors.