Superstition_Free
New member
So I bought a new Rebel 30 head. The tone lacks definition. Notes are buzzy, muddy and have no clarity. Following a thread on this forum, I replaced all the tubes and have attempted to do the bias myself.
The bias pots had a huge glob of white putty around them, securing them to the board (what I took to be the factory setting). I've never seen anything like that. Is this normal? Not being able to get through to support, I decided to carefully scrape that away and proceed (took a while).
I plugged in a speaker, turned it on (warmed up 10 min), set to play, and set the tube mix knob to full EL84. I placed the multimeter probes in TP1 (black) and TP2 (red) and got a reading of .036. I turned TP2 just a little and got no change in the reading. I turn it more. Still no change. I eventually turn it (with ease mind you) more than 360 degrees. Still no change. Same thing with the 6V6s, except they are stuck at .037.
I had the same problem setting the bias on the original tubes. They were off a little, but I couldn't get the setting to change, no matter how much I turned the pots.
How much do these pots need to be turned to see a change? I've spun them 5 full revolutions...Nothing! Any ideas?
Any help is appreciated.
The bias pots had a huge glob of white putty around them, securing them to the board (what I took to be the factory setting). I've never seen anything like that. Is this normal? Not being able to get through to support, I decided to carefully scrape that away and proceed (took a while).
I plugged in a speaker, turned it on (warmed up 10 min), set to play, and set the tube mix knob to full EL84. I placed the multimeter probes in TP1 (black) and TP2 (red) and got a reading of .036. I turned TP2 just a little and got no change in the reading. I turn it more. Still no change. I eventually turn it (with ease mind you) more than 360 degrees. Still no change. Same thing with the 6V6s, except they are stuck at .037.
I had the same problem setting the bias on the original tubes. They were off a little, but I couldn't get the setting to change, no matter how much I turned the pots.
How much do these pots need to be turned to see a change? I've spun them 5 full revolutions...Nothing! Any ideas?
Any help is appreciated.