Had one blown Z44 in PS and one blown 540 in the output.
Rebuilt PS and it is making 82vdc. when using my low amp 12v supply.
Have all 4 outputs in.
When I put it on my high amp 12v PS it tries to cycle on (pegs amp meter on supply then goes back to low draw again and again) but I don't think outputs are starting to switch.
I can read full rail on one speaker output and the other is at ground.
Rebuilt PS and it is making 82vdc. when using my low amp 12v supply.
Have all 4 outputs in.
When I put it on my high amp 12v PS it tries to cycle on (pegs amp meter on supply then goes back to low draw again and again) but I don't think outputs are starting to switch.
I can read full rail on one speaker output and the other is at ground.
Rectifier and outputs are ok
Assumed it was drive. If I take outputs out still get the 82v dc offset on the outputs.
All drive transistors check ok, will keep looking.
Assumed it was drive. If I take outputs out still get the 82v dc offset on the outputs.
All drive transistors check ok, will keep looking.
Not seeing any drive.
Doesnt seem the 4427 is getting any input. It does have Vcc.
Do we know what drives the 4427?
Doesnt seem the 4427 is getting any input. It does have Vcc.
Do we know what drives the 4427?
OK, the transistors likely drive the high-side. It's been several years since I've worked on one.
If you shorted an output fet, the 4427 drive IC often dies right with it. If you don't have drive, that would be my next replacement. You can verify if you have a scope, in my experience there's often a logic level square wave present at the 4427 input pins but nothing leaving.
Attached are pics of the 4 output gate drives (fets out of circuit).
Final pic is Q506 and Q507 gate drive together.
I powered amp up with this drive and it shorted all 4 fets.
Should I put another set of outputs in and pulse the remote and see what the drives do?
Final pic is Q506 and Q507 gate drive together.
I powered amp up with this drive and it shorted all 4 fets.
Should I put another set of outputs in and pulse the remote and see what the drives do?
Attachments
Do the output filter inductors show any signs of overheating like the yellow tape starting to melt?
Intermittent 4.7 resistor on the Hi side drive. Have it stable now but have 18v dc offset on the the outputs.
If you measured 18v across the outputs with the amp on, I think you have another intermittent problem. You should have 40v on all speaker terminals and well under 1v when measuring between the positive and negative speaker terminals.
The legs on the output inductors often broke between the inductor body and the board. This could cause intermittent problems.
As a side note, many times when the inductors overheat, the copper color of the windings can readily be seen through the tape. Yours don't look like they have overheated.
The legs on the output inductors often broke between the inductor body and the board. This could cause intermittent problems.
As a side note, many times when the inductors overheat, the copper color of the windings can readily be seen through the tape. Yours don't look like they have overheated.