Carlsbro GLX100 popping internal fuses

[g1]

Are you measuring the blown IC? If there is continuity with cardboard between IC and heatsink (and screw removed), then the case of the IC is shorted to ground internally. You won't be able to check insulation with a bad IC.
Like JPB mentioned, in addition to the mica insulator, the screw must have the proper plastic insulating bushing.

[TomHoward]

(I thought I had replied but it disappeared so apologies if this is a double post)

The blown IC is still in place, I had missed that - I will replace the IC and re-assemble, and check insolation before I power it up this time. I will check the isolation between hot and ground pads once the IC is removed as well just to be on the safe side.

There was a little plastic screw that was replaced but I'm not sure there's anything on the sides of the screw - I thought the washer should pass into the hole? I have ordered up some new isolation pads and washers in case I need them.

Thanks for your ongoing help with this and my other PA-9336 thread guys. (This isn't my usual area - I am an theatre technician but get round to the repairs a few at a time during quiet times)

[g1]

If the insulating pad (mica or other) was missing, it's possible the thermal grease insulated it for a while, which may be why it didn't blow when first installed. Plastic screws are sometimes used instead of the plastic shoulder washers. Either will provide isolation.
When a metal screw is used with the shoulder washer, then the washer does press into the hole, with the shoulder staying out and insulating the head of the screw.

[TomHoward]

Thanks guys

There is an adhesive pad on the heatsink but I didn't test the integrity of it.

I have attached photo of the IC in place (this is the 2nd blown one)

[52 Bill]

There is an adhesive pad on the heatsink but I didn't test the integrity of it.

That looks like a Mica insulator. It is clearish when cleaned. The white goop is heat sink thermal compound. You must have both.

What I can't tell is if the black washer under the mounting screw is a plastic insulator or just a plain old metal split ring lock washer.

[carlbontoff]

Circuit Diagram

Thanks guys

There is an adhesive pad on the heatsink but I didn't test the integrity of it.

I have attached photo of the IC in place (this is the 2nd blown one)

[ATTACH=CONFIG]27884[/ATTACH]

Hi Guys,
Does anyone have a circuit diagram for this amp? The pcb is PC03076 and it is used on the PM10 monitor.

Thanks.