It's a type 2 class D amplifier.
I've rebuild the whole driver board. New transistors, new caps, new ic, new diodes.
Even with no output mosfets in at the mainboard, the high side parallel emitter follower pair on the driver board are getting scorching hot in seconds and destroyed. No issues at the low side.
I've noticed also the cap in the red circle is getting bulged every time i power up the amp. I'm using 35v 47uf low esr cap, and there should not be so much voltage across it so it would bulge.
Driver Board Pin-Out are as they should be comparing it to the Perry's Manual.
With the driver board out, rail voltages, +-15, everything looks fine, i do have the proper sinewave at the +In:Audio input to the driver board.
I haven't changed only the ZD6, as I don't know what it is, but it measures just fine.
Any ideas where to look ?
I've rebuild the whole driver board. New transistors, new caps, new ic, new diodes.
Even with no output mosfets in at the mainboard, the high side parallel emitter follower pair on the driver board are getting scorching hot in seconds and destroyed. No issues at the low side.
I've noticed also the cap in the red circle is getting bulged every time i power up the amp. I'm using 35v 47uf low esr cap, and there should not be so much voltage across it so it would bulge.
Driver Board Pin-Out are as they should be comparing it to the Perry's Manual.
With the driver board out, rail voltages, +-15, everything looks fine, i do have the proper sinewave at the +In:Audio input to the driver board.
I haven't changed only the ZD6, as I don't know what it is, but it measures just fine.
Any ideas where to look ?
Attachments
No, no shadows, darkening, carbonization or burnt traces, board seems fine, I could not find any heat related damage to the driver board.
If you remove the 150 ohm resistor that connects the high and low-side drivers, do the A42s heat up?
Redid the whole board once again.
Now the low and high side drivers does not heat up even with mosfets in, but the amp is cycling in and out of protect, seems there is DC at the output.
Oddly I found that I do not have -15v once i do fit the driver board....i do have positive + 4.2v instead of -15v at the -15v pin of the driver board. But the op amps in the pre amplifier are having proper -15v, so i assume it's something at the driver board.
If i remove the driver board, the via for -15v is having the proper -15v. I suspect a leaky transistor ? The only ones that are getting hot are these at the attached photo. Especially the one at the edge of the board.
I've already pulled them out, tested them at the LCR meter, they show just fine with over Hfe>150 but that's not a clear indication they are fine....maybe they are leaky but once high voltage is applied to them ?
Sadly i do not have any more 2sc1027 or 2sc2383 (which i'm using right now)
I do have only some sony 2sc1670.
Now the low and high side drivers does not heat up even with mosfets in, but the amp is cycling in and out of protect, seems there is DC at the output.
Oddly I found that I do not have -15v once i do fit the driver board....i do have positive + 4.2v instead of -15v at the -15v pin of the driver board. But the op amps in the pre amplifier are having proper -15v, so i assume it's something at the driver board.
If i remove the driver board, the via for -15v is having the proper -15v. I suspect a leaky transistor ? The only ones that are getting hot are these at the attached photo. Especially the one at the edge of the board.
I've already pulled them out, tested them at the LCR meter, they show just fine with over Hfe>150 but that's not a clear indication they are fine....maybe they are leaky but once high voltage is applied to them ?
Sadly i do not have any more 2sc1027 or 2sc2383 (which i'm using right now)
I do have only some sony 2sc1670.
Attachments
Okay....found the issue....there is no -15v connection to the driver board....but if I pulled it out and measure the via there are -15v....I guess it's burnt somewhere in the epoxy. Installed a jumper wire and now works fine....
When I got the amp the blue resistor in the picture attached was badly burnt and the area around it. I've cleaned it up and could not see any broken traces. Replacing the resistor I did not think at that point the damage could be more severe like in the board or around the vias.
