Alpine mrv-f357 thermal

[Kenc17]

I have this 5 channel amp and i need help please! The amp turns on, plays but sounds bad for about 2 min then shuts off, thermal. Have tested speaker leads speakers and power. The 3 capacitors in a tight group by the power input are very hot at that point. The toroid?? Also seems hot. Any ideas? What should i do? Circuit board seems a little discolored in this area, but nothing visibly burnt front or back.

[Perry Babin]

Let it cool completely.

Disconnect the RCAs and all of the speaker wires from the speaker terminals on the amp.

Power it up and let it idle. Does it get hot?

If it does, make a note of which section of the top of the amp heats up the quickest.

Don't leave it on long enough to thermal. Just leave it on long enough to see if it starts to heat up.

[Kenc17]

Ok just checked it out it heats up with just power ground n remote connected. The 3 caps mounted close together are the hottest. What next?

[Perry Babin]

Did the heatsink get hot?

[Kenc17]

Yeah the heatsink was also hot on the same side by the power inputs

[Perry Babin]

With no power applied, check all of the transistors along the other side of the heatsink. Measure the resistance between the legs of each individual transistor (leg 1 to leg 2, 1-3 and 2-3). Do any read anything near 0 ohms?

[Kenc17]

The larger ones on the side that wasnt hot? Ill check tonight

[Perry Babin]

Check ALL of the transistors along the side with the larger transistors.

[Kenc17]

Tested all on that side, the one farthest from the wire connection side is the only one that shows anything close to 0.
1 to 2. 23 ohms
1 to 3. 8 ohms
2 to 3. 16 ohms

[Perry Babin]

Q489?

Pull it and check it out of the circuit.