Tube Amp Head Loud Humming?

[joshw1200]

I'm currently playing a Schecter Hellwin Stage 100 with the corresponding 4x12 cabinet. As of just yesterday, It has been giving off a loud buzz/hum any time it is not on standby. The hum does not stop even when all of the knobs are turned all the way down. Does anyone know what this could be or how to fix it? If you have any other questions, let me know.

[onelife]

Does the hum change if you turn the volume control up or down? (you may need to have the tone controls up a bit for this test)

 

If the hum is not affected by the volume (and tone) controls on the amplifier then the most likely culprit would be the filter capacitor in the circuit for the negative bias on the power tubes. Another possibility would be a defective power tube or perhaps even a noisy preamp tube.

 

Try checking or changing the tubes first. Look to see if the power tubes light up evenly.

 

f you are not experienced in changing filter caps in a high powered tube amp then take it to someone who is.

[WRGKMC]

Onelife is right. I will also add it can be a blown grid resistor on a power tube. Look and see if any of the power tubes glow orange. If so you need to replace the power tubes with a matching set, have them properly biased and get the cause of the tubes blowing fixed.

 

Hopefully the cab impedance does match the heads impedance. If the impedance is too high it can cause tubes to blow prematurely, ie a 4 ohm head pushing a 16 ohm cab.

 

Or the problem can be a simple solder joint that's cracked. Heads get allot of cab vibration and it can crack a solder joint if it wasn't soldered well to begin with. I had a friend give me Music Man head a year ago. He said it hummed badly and barely had any output. I confirmed that was the problem, opened it up, started checking connections, and found a B+ wire on the tube socket loose. Re-soldered it, plugged it in and bammo, it was running like new. I had a $700 mint condition amp head for free.