AMPEG TUBE HEAD Problem!

[Saosinfftl]

I have an Ampeg SVT- CLassic, its the remake model and my problem is, when i cut it on all the tubes light up, but when i take it off standby, 2 of the 6550's flash blue then the amp goes into fault. what could be wrong with it?

Iv looked at the bias lights to make sure it was great, but as soon as i take it off standby the lights go out too.

[Enzo]

So remove those two tubes and fire it up without them. Now what happens?

You cann't bias the amp while it is in standby. The bias adjustment relies upon the tubes conducting.

[Saosinfftl]

i did and now it doesnt go to fault. and i also switch out the tubes i thought were bad but when i put the good tubes in they started glowing blue and it went to fault. wat could it be?

[Enzo]

Are you telling us that no matter which tube you use, the ones in those particular sockets have trouble, but the same tubes work OK in other sockets?

If that is the situation, then something is wrong in the circuits for those sockets. Perhaps an open resistor is taking the bias voltage away, or maybe a coupling cap is leaky. Hard to say. I would check the voltage at each pin of those sockets and compare to what the good sockets show.

[Amp Kat]

Sounds like you may have some problems if those tubes your subbing are good. I would have a tech look at it to resolve the fault issue. Could be several things unless you have some electronics background on you. Still sounds like you have a bad tube and blue glow is normal but flashing isn't.

[Saosinfftl]

yea i checked all the sockets voltage outputs and they are all the same, and i checked for shorts and there werent any. so i dont think its the sockets. but the tubes still glow blue....

any suggestions?

[Saosinfftl]

yea i check the voltage in each pin of the sockets and all of them were pretty uniform.

[Amp Kat]

Your problem is something is shorted on the main board or possibly the preamp board but I doubt it. Whether it's one of the 10 ohm resistors or in the LED circuitry something is shorted causing a fault . Try pulling 4 of the six tubes and see if the fault goes away. You can run it with 2-6550's. One on each side and see if it will come up with just two.