New tube problems - need help


A few weeks ago i shorted an output tube on my Quicksilver mid-monos.

This afternoon I finally got around to replacing the tubes with a brand new set (matched quad) of of eh-kt88s.

the issue is that since I installed the new tubes in the amps I am unable to bias the amp that shorted? No matter the bias setting the led indicator light for the bias never lights up.

By feel, it seem that amp is running hotter as well.

The amps sounds found fine, the image is centered and the dynamics are spot on.

Do I need to worry?

Any idea what the problem may be?

I will start to swap tubes between amps to see if it is tube issue or internal wiring problem. Once done i will report back.
nick_sr
Yes you need to be concerned. Did you check all of the fuses? You may have done damage to the amplifiers circuit for that tube, typically a resistor might get taken down with a blown tube. I think it would be prudent to refer the question to Quicksilver, even if you haven't bought it directly from them.
I switched tubes and the problem remains with the amps.

I did check the fuse and changed the fuse before installing the new tubes. It was fried after I shorted the tube.

Initially when I first shorted the tube, I contacted Quicksilver. They confirmed that the tube was shorted and said that all I needed to do was replace the tubes.

One more issue regarding fuses. This whole problem started when I blow the fuse. No doubt because the tubes had reached the end of their life.

When I replaced the fuse and powered back up the amp it is then that I shorted the tube. I question whether the replacement fuses that I am using has something to do with the problems or damage. The fuse rating is correct but the fuse construction of the factory fuse appeared far superior to the replacements.

One final note, with the bias dialled down the difference (relative to the other amp) in the heat generated by the power transformer is significantly reduced.

Thanks Mechans, Monday the amp will go for service.
Sometimes a grid resistor will fail when a tube goes. Also it's a good idea to replace the phase inverter tube when doing the power tubes (if your amp has one, that is)
Open the bottom and look for a blown resistor, cant miss it. A big splat on the bottom. You might have a bad pot so move it back and forth several times and this will clan the brushes. Then you will have to consider the pot is bad. Be sure the tubes are matched.
Is it possible that the quality of the fuse could have contributed to the failure of resistor? That is, if the fuse would have blown earlier would this have protected the resistor?