poweramp problem?

I haven't biased my RM100 combo in a while. I got a new pair of kt66's and went to install/bias them and I think my amp has a problem.

First, one of the lights came on saying i had a tube failure. First I swapped positions of the KT66's and had the same result. Then I tried EL34's and 6l6's in the same spot and got the same result. I also couldn't get a reading on my multimeter. The tube failure light seems to go on no matter what tube I have in there.

Problem 2 is when I went to check the bias on the two tubes I've been using (i've been running the amp at 50 watts) I couldn't get a reading from one of the test points.

The fuses seem to be fine.

What's going on with my amp?

Several things:

- You need to pull the fuses and check for continuity with a meter. If a tube failure light is on, the fuse should be gone.
- You should also look at the internal fuses for the heaters, as one of them may be bad.
- I believe I mentioned to you when your amp was here that running the amp with two tube pulled requires you to set the impedance selector at half of what your speaker load actually is.

Start there and report back.

Jaded Faith said:

Several things:

- You need to pull the fuses and check for continuity with a meter. If a tube failure light is on, the fuse should be gone.
- You should also look at the internal fuses for the heaters, as one of them may be bad.
- I believe I mentioned to you when your amp was here that running the amp with two tube pulled requires you to set the impedance selector at half of what your speaker load actually is.

Start there and report back.

Click to expand...

1, What kind of fuses do I need to buy? Can I get them at home depot or radio shack? Should I replace all the fuses?
2, I've never looked in the rm100 chassis. Where are the internal fuses?
3, That's been taken care of. My 2x12's are running at 4 ohm's and my 4x12 is running at 8.

So I replaced the broken fuse. I put a set of KT66's in, biased at 34-ish. Is that a good setting for them? They give my sound great clarity.

However, I still can't get a bias reading for one of the tubes. What's going on?

I would say anywhere between 32-36 is just fine for those tubes.

As for no reading, there are a few things it could be. Most obvious would be a tube failure light and blown fuse. If that's not the case, I'd want to look at the test point itself to see if that was broken, pushed into the chassis or not making a good contact. I'd also want too test the socket for plate voltage, but not if you aren't experienced and comfortable doing so safely. I would also suggest using the other pair of sockets (inner or outer) to see if it's all good there.