RE: Somehow it involved a fuse

I reinserted tubes to start measuring bias and thought again about the fuses. Visually they all looked intact but when I used the continuity tester one of the two 5A slow blow fuses on the front of the amp was not making the short and the ohmeter showed infinite resistance. Strangely when I measured grid voltage on all the tubes at pin 4 they all showed 184-5 on the left and 181-2 on the right, even without the left fuse in circuit. With the fuse out I depressed the voltage offset switch and even without that fuse it was pinned at zero. I put a new fuse in to its place and listened and it sounds good. I think that pulling and reinserting the fuses or the tubes must have cleaned some crud off of something to make the difference. Otherwise the tubes that I thought had to be balanced one row of six to the other row I now know have reinserted to be balanced left to right. Now offset is at zero and sound is balanced between the two amps. No explanation readily available but sound is back.

As an aside to Ralph, are there any different roles played by the five 6sn7 tubes that would let me know which needs to be least microphonic, which needs the best plate to plate match or if any of the tubes need to match one another. On my amp, looking from the front, the rightmost tube is next to the xlr jack and the leftmost tube is next to the offset meter.

Thanks again for the advice.

Charles

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Follow Ups Full Thread

Topic - Got the DC-offset blues - ChasLieb 20:47:23 09/24/15 (23)

Chas, how about some pics of this unusual amp, pls? (NT) - jeffreybehr 15:29:47 03/20/16 (0)

Are all the power tubes OK? - Ralph 10:29:26 09/25/15 (13)

RE: Are all the power tubes OK? - ChasLieb 13:52:30 09/25/15 (12)

OK- its an older 12-tube model - Ralph 14:10:27 09/25/15 (11)

RE: OK- its an older 12-tube model - ChasLieb 14:34:03 09/25/15 (10)

RE: OK- its an older 12-tube model - Ralph 13:17:23 09/28/15 (9)

RE: OK- its an older 12-tube model - ChasLieb 18:42:31 09/28/15 (8)

RE: OK- its an older 12-tube model - ChasLieb 18:52:46 09/28/15 (7)

All the 6SN7s must be in place and as many of the power tubes as possible. - Ralph 09:28:56 09/29/15 (4)

RE: Somehow it involved a fuse - ChasLieb 17:16:52 09/29/15 (3)

RE: Somehow it involved a fuse - Ralph 18:29:25 09/29/15 (2)

RE: Somehow it involved a fuse - ChasLieb 19:01:39 09/29/15 (1)

RE: Somehow it involved a fuse - Ralph 10:02:22 10/01/15 (0)

RE: OK- its an older 12-tube model - Lew 06:42:09 09/29/15 (0)

RE: OK- tested the grid voltages on all 6as7 sockets - ChasLieb 19:05:35 09/28/15 (0)

As I always advise in situations such as this,... - Lew 07:36:03 09/25/15 (7)

RE: As I always advise in situations such as this,... - ChasLieb 14:01:09 09/25/15 (6)

On a 12-tube model the power tubes are in banks of left and right. - Ralph 13:04:52 09/28/15 (2)

RE: " the power tubes are in banks of left and right." - ChasLieb 19:15:52 09/28/15 (1)

RE: " the power tubes are in banks of left and right." - Ralph 12:14:09 10/06/15 (0)

RE: As I always advise in situations such as this,... - Lew 13:19:47 09/27/15 (2)

RE: As I always advise in situations such as this,... - tanics 00:18:18 09/28/15 (1)

Interesting... - Lew 07:30:12 09/28/15 (0)

Follow Ups

RE: Somehow it involved a fuse - ChasLieb 17:16:52 09/29/15 (3)

RE: Somehow it involved a fuse - Ralph 18:29:25 09/29/15 (2)

RE: Somehow it involved a fuse - ChasLieb 19:01:39 09/29/15 (1)

RE: Somehow it involved a fuse - Ralph 10:02:22 10/01/15 (0)

RE: Somehow it involved a fuse

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