Gallien Krueger Fusion 550

[GordB]

Hi guys. I'm looking for some help with my GK Fusion 550. It's a class H solid state power section with a 3 12ax7 tube preamp. I have done a search but haven't found a schematic or service manual.

Last night it slowly lost power and then emitted a burning smell. The amp lights up and all the tubes glow. The motorized knobs and channel switching are working.

I ran direct from the bass to the return jack and got no sound. I then ran from the send jack to another amplifier and did get sound.

So it appears the preamp is working. I found two resistors located near the back panel of the amplifier numbered R48 and R49 that look burnt.

Thanks in advance.

Gord B.

[Enzo]

Did you contact GK directly and ask for schematics?

[GordB]

Enzo, I did contact them but my query was about finding a service centre in Canada as they have none listed on their website.

They advised me to speak to the retail chain where I purchased the amp. This retail chain referred me to a shop I have dealt with before and had good service from.

Internet wisdom infers that the power section of this amp is similar to the power section of the 700RB, but that is not enough to go on.

Over and above this, I plugged another amp into the cabinet he uses and got no sound. I pulled the crossover plate out and both fuses are blown.

What a day!

[52 Bill]

Over and above this, I plugged another amp into the cabinet he uses and got no sound. I pulled the crossover plate out and both fuses are blown.

What a day!

The problem with the amp may have caused the fuses to blow. There could have been dc voltage on the output that would have been sent to the speaker cab.

You will need to test the speakers as well.

[Enzo]

And not to get too pedantic, but asking for a service center is not the same as asking for a schematic.

[GordB]

The problem with the amp may have caused the fuses to blow. There could have been dc voltage on the output that would have been sent to the speaker cab.

You will need to test the speakers as well.

This operation is on the table for today. The fuses are 12v 15w bulbs for automotive lights. Last night I went to three separate auto parts stores nearby and none of them had them. It appears there is a marine supply store close by that may have them.

This morning I will test the resistance of the speakers and then do a 9v test.

[GordB]

And not to get too pedantic, but asking for a service center is not the same as asking for a schematic.

It doesn't appear pedantic, Enzo. More thorough. I haven't asked them yet, but intend to this morning. I won't hear back until Monday at the earliest. In the meantime if anyone there is reading this and you have the schematic, please chime in.

[GordB]

Just a quick update on this amp. Two resistors in the output stage were burnt and there was a loose connector from the preamp to the power amp. I was renting a 1001RB while this one was down and it appears the power amplifier PCB's are identical, based purely on the fact that the PCB model number is the same. I found a schematic for it.

The cabinet itself had an intermittent connection between the woofer's voice coil tinsel and the spade terminal card. I was sure the speaker was shot but probed all the way back to the voice coil leads and got a response. I secured the connection and it's now fixed. Crossover is working fine in both biamp mode and full range.

BTW, This type of fuse was not readily available in the voltage, wattage and size required.

Anyways, it's working again. Thanks everybody.