S.E.X. 3.0 Voltage problem (resolved)

[kevinlei324]

I just finished my SEX build, but have a voltage issue.

Lead 17 is reading around 145 mv

20, 21, and 24 are all about 20 v higher than what the manual specifies:
20 - 405 v
21 - 420 v
24 - 400 v

Everything else seems to check out... I attached some pictures to see if that might help.

Any help is appreciated!

Thanks

 

[Paul Birkeland]

What is your AC line voltage and which range did you use in the manual?

-PB

 

[kevinlei324]

AC line is 120 V. I used 115 to 130v.

 

[Paul Birkeland]

What DC voltage do you get between H4 and H5?

 

[kevinlei324]

I'm getting 6.39 v between h4 and h5

 

[Paul Birkeland]

Alright, my thinking was that low voltage between H4/H5 could cause a drop in the current the circuit draws, and that would pop your high voltages up a bit, but you have plenty of voltage there.  I suspect that there are no issues here, and that you might find that your wall voltage is wandering a little bit between 120V and 125V.

-PB

 

[kevinlei324]

Alright, I just plugged it in, and everything seems to be in working order. Headphone and speaker out seem to be working great! There some noise in one channel, but it seems to be tube-related, since swapping the tubes switches the noise to the other side.

Just for my own learning... But why would there be such a large difference between what I'm getting at terminal 17 from the expected reading and still be in working order? The wiring category is for 115v - 130v, so I don't see how the fluctuation of my AC line between 120v and 125v would cause such a large.

Thank you very much for your help!

 

[Paul Birkeland]

Can you measure the DC voltages at 13 and 31? 

 

[kevinlei324]

13 - 392v
31 - 3.02v

 

[Paul Birkeland]

Sorry, I meant 13 and 21.

 

[kevinlei324]

oh, 21 is 420v

 

[Paul Birkeland]

The common B+ rail leaves terminal 33, then splits off to both channels. One side is terminal 13 and the other side is terminal 21.  Can you measure the DC voltage at 33?

These should not be so far off but understanding which one is the problem will depend a little on what your raw high voltage rail looks like. 

 

[kevinlei324]

I'm not sure what happened, but the issue went away... I didn't do anything at all other than play some music through it. But here are the new readings as of everything working. Terminal 33 was 416v. Thanks again for all your help!

2 - 82.0v
3 - 18.78v
4 - 28mv
5 - 0
6 - 380v
7 - 396v
10 - 372v

16 - 81.0v
17 - 18.36v
18 - 33mv
19 - 0v
20 - 380v
21 - 396v
24 - 373v

H2 - 3.25v
H4 - -3.07v
H5 - 3.25v
H7 - -3.08v

Additional:
Between H4 and H5 - 6.32v
13 - 396v
33 - 416v