Mashall mg100hdfx power chip board replacement

[jessadr]

Got my new power chip board assy in. The old one had been removed and just laying in the case. Do I need to use a mica insulator , screw insulator and grease on the heat sink ? Nothing was left with the old one.
The preamp works good. The old chip had pins melted on the board. Should I drill some holes under the board to get a little more cooling air.
Thanks

[soundguruman]

Got my new power chip board assy in. The old one had been removed and just laying in the case. Do I need to use a mica insulator , screw insulator and grease on the heat sink ? Nothing was left with the old one.
The preamp works good. The old chip had pins melted on the board. Should I drill some holes under the board to get a little more cooling air.
Thanks

The heat sink is hot, (as in energized) the plastic fan insulates the heat sink. There is no insulator.
The best heat sink compound for that amp is the arctic silver, sold in computer stores, or at radio shack, etc...
Newegg.com - Arctic Silver 5 Thermal Compound - Thermal Compound / Grease
however, don't get the silver on the electrical connections, it's sort of conductive. (you can wash it with denatured alcohol)
anyhow, the silver dissipates heat much faster than ordinary zinc grease...
The best way to deal with this is to buy the chip already mounted on the board. It's a regular Marshall part.
However, the board chip assembly is a bit hard to find and order, but worth the extra price. I suppose the places that have it are charging a premium. It saves a lot of headache and circuit board work...
Then as far as cooling goes you can speed up the fan...or customize modify it...
The part that usually blows along with the output---is a zener diode in the power supply, that regulates the voltage for the standby pin...

Then what to watch out for is the speaker load. It can be no lower than 8 ohms, or the IC overheats.
Some people have swapped out the speakers and wired it 4 ohms, then the IC flames.