Stereomour 45 build, high voltage terminal 2, OA [resolved]

[maryc27182]

Hi folks, how are you?

As the subject says, this is a Stereomour configured for 45s. All resistance checks are good; voltages are good except for terminal 2, where I read 270V, and OA, where I read 269V. (Oh, one other data point, I'm testing this with the 2A3 tubes--didn't want to test with my 45s. The voltages that tested good are in between those listed for the 45 and 2A3 on the check list.)

I'm reading 170V at terminal 14, and 171V at OB, for comparison purposes.

Anyone have any hints or debugging ideas? Thanks much.

Mary

[maryc27182]

I remembered I had a couple other 12AT7 and threw one in.

Now terminal 2 is about 200V, OA similar; terminal 14 about 186V, OB similar.

Should I try to track this down further, or are the two sides close enough for me to proceed?

Mary

[Paul Joppa]

200 and 186 are fine - this value varies more than most from one tube to another, or between two triodes in one envelope (the 12AT7). In fact, 270 and 170 are within the reasonable range - and there's a good chance the 270 will drift down over the first ~100 hours, as the cathode chemistry stabilizes.

Nevertheless, the closer match of the second tube might possibly be audible - why not listen to each of them once the amp's stabilized? We'll all be interested in what you hear or don't hear!

[maryc27182]

Thanks for the information. I appreciate the response!

Mary