Cary SLM-100 Bias in Triod Mode

I had a similar problem with fuses blowing. I was at witts end. I purchased a set of EH tubes from The Tube Store that were matched. Low and behold, the problem stopped. It may be worth a try.

Pawlowski, is the problem with one amp or both mono-blocks? If you are only blowing fuses in one amp, then swap all of the tubes from one amp into the other and see what happens. If the fuse blows on the amp that had previously not been blowing fuses, then you have a problem with the tubes. If the original amp, with the swapped tubes, continues to blow fuses, you may have a problem with the power supply. Another way to check tubes verses power supply is to disconnect each amp from any load (disconnect the speaker cables,interconnects, but of course plug the amps into the wall), remove all of the tubes, and turn the amps on. If they blow the AC fuses, you have a problem with the power supply. If they do not, you have a problem with the tubes. Check with Dennis at Cary before doing this, but I believe you are ok operating the amps with no load. Hope all turns out well.................

SNS, thanx. In fact, one set of tubes ddid get all excited (really bright) before the fuse blew. I changed all eight power tubes and was OK for a few days. Since then, with the different (not NEW) tubes experienced blown fuse twice. I didn't notice them getting bright, although they may have and I didn't notice, but did notice the creeping bias. Thanx for the thoughts.

Pawlowski, I used to own the SLM 100's. I recall biasing them at 150 per Cary's instructions. I think this is especially important if you're using EL34's. The rising bias could be due to a bad bias circuit resistor. I had that problem with one of my monoblocks when it kept on blowing ouput fuses. In my case I also ruined some output tubes. If your tubes have glowed cherry red prior to fuse blowing you may have some iffy tubes.

In addition to getting your info here, you can call Cary Audio for their analysis, and advice. One of the manufacturers that provides best customer service even when you are not the original owner.