Strange thing happens when I bias my amp

I have an SLI-80 F1 and have never had any issues biasing a variety of tube types. I haven't seen the behavior you're describing.

I would agree with Celtic's recommendation to look first at the multimeter itself and test with a different meter. You can get a Craftsman meter from Sears for around twenty dollars that should work well enough to see if the issue is with the amp or the meter. There's a Fluke available on ebay for $28 that might be better than the Craftsman.

Advice from Cary's service department has always been good but for an issue like what you're describing I'd be willing to bet they'll want you to ship the amp to them. That's an expensive and potentially risky proposition because of the risk of shipping damage. As you know, Cary's packaging is very good but that's a very heavy amp.

What kind of tubes are you biasing at 100 mA? The manual says 75 mA without mentioning the tube type and the advice I got from Steve at Cary suggested 65-70 mA for El34 and 6L6 tubes.

Angiernc - I was looking at my manual, as well, when I quoted the 75 mA recommendation. Perhaps the F1 model I have is different from the standard model or maybe recommendations changed during the course of production. I definitely got the recommendation of 65-70 mA directly from Steve Witek at Cary, wrote it down in the back of the manual while I was talking with him.

I wasn't trying to make an issue of the bias value, I was just curious since the 100 mA figure was different from both what was in my manual and the verbal advice from Steve at Cary. The real issue here, of course, is the erratic behavior during biasing that Dbrewer12345 is experiencing.

Dbrewer12345 - One thing I forgot to ask in my first post is whether you're using an analog or digital meter. Don't know if that makes any difference but my experience with the SLI-80 is only with digital meters.