Badcat Making weird noises

[Mattlee0037]

So my friend purchased a used Badcat cub iir (which I have been unable to find schematics for, and I'm having trouble figuring out what is making all these noises. Note: he said it didn't used to hum so bad- it was shipped and then it started.

First off I believe the most of the noise is in the preamp section. When I pull what I assume to be the PI tube all the noise stops.

Noise 1: There is pretty much always 60 cycle hum coming out of the speaker at all times regardless of anything. This comes with or without PI and does not vary with volume.

Noise 2: Preamp static. This varies with volume knob and how much is signal is being fed into the preamp. This gets really loud in a signal to noise ratio. Makes it very difficult to use because of the level.

Noise 3: Reverb noise. This amp has a tube driven spring reverb. I assume this is what 2 of the 12ax7's out of 5 are for. This noise is much higher pitched and squealy. It starts this noise when the reverb knob is turned on regardless of if the tank is connected. In this section there is a capacitor connected to the output of Pin 6 of V3 to resistor cap in series into the PI tube. If this 2n2 capacitor is moved into a certain spot the amp freaks out and makes crazy whirling spaceship noises out of the speaker.

Any advice is very welcome. I've read Dave Hunter and Gerald Weber's books and am aware of how to safely drain caps and operate on amps this is just the first time i've run into these problems and I'm kind of taken aback.

Thanks everyone!

[dorrisant]

How is the bias set? Any redplating?

[M Fowler]

I actually would email or call Badcat for advise. I always contact the manufacturer when I get in an amp with issues.

Mike Soldano sent me a new red jewel lens free for a 20w Jet City after we discussed bias issues when I asked if the threads were metric because I can't find a lens that works.

Dr Z's techs discuss problems with EZG50 amps with me and suggested switching JJ rectifier to Sovtek because of problems.

Called Savage Audio near me about one of their amps I was checking over and had a great conversation with them.

It pays to contact the builders. Hopefully someone can chime in here to help you as well.

Mark

[Mattlee0037]

Nope no redplating. I can check the bias for sure! I will try to get in contact with Badcat as well!