Gamut amp acting as a sparkler!

[aptquark]

Hello all,

What started out as a very low hum from one channel of my D200MRKII, developed into a sparkling fireworks show later on. I took the circuit board out and noticed a SCHRACK relay had burned up internally. See pic. Nothing else looks damaged or broken on the board. I ordered a new SCHRACK relay and was wondering if this will be a simple plug n' play fix. Any comments before I fire this thing up?

 

[bob91343]

I thought I answered this one. That relay contact is burned badly and it's probably because of a fault in the amplifier. Check that out before connecting speakers.

 

[aptquark]

Bob...too late with the speakers. That side is burned out (speaker that is). Any ideas as to where I can start checking?

 

[bob91343]

Yeah those power transistors are where you start. If you find bad ones, don't stop because when they fail they take out other components.

Best to get a diagram or, at least, make one.

 

[aptquark]

Bob, I checked those transistors. They are MJE340's and MJE350's (NPN and PNP respectfully.) They measure like they should with a diode check (about .680 with the correct orientation and open across the rest.) Any other ideas?

Thanks in advance

 

[bob91343]

Measure the voltage from the amplifier output. It should be zero. If it is, there is either an intermittent failure or some strange transient melted your relay contacts.

You need to make sure the amplifier output is zero with no signal, and that the idling current is about right. If it all checks out, you can replace the relay but I'd add a fuse in series with the speakers in case this happens again.

 

[aptquark]

Fellas,

Quick question...see those transistors in the pick? Do those need non-conducting thermal paste when mounting? ALSO...the HUGE MOSFETS that the Gamut uses (2 per side)...do those also need the same type of paste?

 

[ANADIGIT]

Solve problem ?

Hi,
Does your problem had been solve ?

An externally hosted image should be here but it was not working when we last tested it.

If not, I have service manual and wiring diagram to help you.
Reimyo KAP-777 as same as D200I, too

Thanks
Marcus