Plate currents in P-P

[rsumperl]

Good morning everyone,
So, out of curiosity I checked the individual plate current on a set of 6LX6's in P-P, one tube was at 43 ma, the other was at 24 ma. Obviously not a good situation. I put a set of 6LB6's in and the difference was only 1 ma. So, the question is do I have a bad 6LX6 or is that a normal spread for sweep tubes?

Thanks,
Ray

 

[SY]

Is that in a Millett red board amp? If so, that's bigger than any spread I've seen with 6JN6. I've also seen (in a different amp) much closer matching in randomly chosen 6LF6, which is pretty close to your tube. I think you have at least one outlier.

 

[roline]

I had one 6LB6 that refused to be biased controlled down to -60V. Then it was at 90ma, at best. It is marked as a flyer and I do not plan to use it... The rest were down around -42V for 45ma.

 

[Miles Prower]

So, the question is do I have a bad 6LX6 or is that a normal spread for sweep tubes?

I'd say so. The only time I saw 6BQ6s (another type of sweep tube) with currents that far off, it was due to gassiness. Current shouldn't run away like that for any type of VT.