25% high voltage at A5 (follows tube)--weak tube?

[maryc27182]

Hi folks, how are you? As the subject says, I'm testing my stock build and am measuring 25% high on A5 (94V) which follows the tube when I switch between sockets. A cursory search of the forum indicates that tubes nearing readings of 100V at A5/B5 may be a cause for concern (regarding the tube, probably not so much the circuit.)

Resistance checks were good, and the rest of the voltage checks were within 15%.

Any input would be appreciated. Thanks,

Mary

[Doc B.]

Sometimes a tube needs to cook in for a while before the cathode emits the proper electron cloud. You might try running the amp for a while - maybe 10 hours - and remeasure.

[maryc27182]

Thanks, Doc. Will do.

[maryc27182]

Hi folks,

After 10(ish) hours of cooking, the 94V dropped to 93.2V. The other tube stayed constant at 71V.

The amp sounds fine on my speakers (dorm-fridge-sized 2-ways in a small room--my "bedroom" system where my Stereomour 45 lives.) I haven't tested headphones yet, as I mistakenly left those at work.

So. Should I not worry about the 25% high measurement and see how long the possibly-weak tube lasts? Find a $6 replacement that measures better?

Mary
p.s. As you all know, this amp is stunningly quiet, even on my v. efficient compression drivers. This has got to be the least noise I've heard through my horns (even though that's not going to be how I use the S.E.X. amp--my Stereomour 45 is going back into the bedroom system posthaste, and the S.E.X. to the office as a headphone amp come Monday.)

[Doc B.]

Yeah, if it sounds fine don't worry about it. The voltage may continue to drop with more use.