Ampeg Svt cl bias red light

[sharpiemarker]

A few months ago I posted about this and instead of taking it to a tech I decided to buy three power tubes. I believe the answer to my problem is take it to a qualified tech. I was just hoping that there is a slight chance someone here will know what to do.

bais 2 on my svt would have the red led come on first before the green led. According to the manual that means one or more tubes is not matched. A few months ago my amp finally went into fault mode. Today I replaced a set of three power tubes. I am not able to set the bias now. I can only get the red light to come on on bias 2. I tried swapping the three new ones on the right with three old ones on the left. The the lights don’t change sides with the tubes. I tried swapping drive tubes, no difference.
I can’t get the amp to go into fault mode now. I’ve been playing it loudy for almost two hours. Sounds right to me. I set the bais so I have no hum/ buzz. Bias one is set and acting properly, bias two still has the red led on I can’t get the green to come on no mater where I set it.

I won’t get offended if you assume I haven’t done the basic trouble shooting. The tech I want to take it too is not taking any Amps until they work through there back log

thanks

 

[rickdog]

Just to be sure: do you know which tubes sockets are on the same bias control? Look at the tubes as two triangles: each triangle has its own bias control. It's not organized as front row/back row.

If you've swapped the correct sets of tubes, and bias 1 can always be set correctly while bias 2 cannot, there is an internal problem in the amp. A likely possibility (based on experience with my SVT-CL) is that the screen resistor for one of the tubes on the bias 2 side has failed. That disables the tube (no current flows) so you can never get a green light. A tube that shorts or arcs internally will trigger fault mode, and can also blow out the screen resistor (ask me how I know). There are other things that can cause this symptom, though.

Sorry to have to say this, but I think it's tech time.

 

[agedhorse]

Almost certainly tech time, before you cause more damage.

 

[sharpiemarker]

Thanks for the advice everyone. I have finally found a great tech that I trust. It is going to then soon. If I remember I’ll post what the issues actually is