Another failed voltage check

SamJ · 498

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Offline SamJ

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on: July 10, 2025, 11:22:06 AM
Same as figby, after a good resistance check and lots of comparing picture to result, I have some wayward DC voltages. Of note the two LEDs for the right channel aren't lighting up.  I reflowed all the connections, including at the terminal strips.  All tubes glow normally and I haven't had any pops or buzzing, smoke, etc.  I'm sure I screwed something obvious up. 

here are my wayward voltages:

14. 1.856 (170-230)
15. 0.302 (58)
17.  1.007 (0)
19.  2.996 (395)
20.  2.848 (365)
34.  3.014 (392)
36.  .305 (58)
37.  .302 (58)
39.  .302 (58)
40. .299  (58)

Sam


Offline Paul Birkeland

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Reply #1 on: July 11, 2025, 05:01:09 AM
Do any of the 130 ohm 2W resistors measure open when you check them with your meter (with the amp off)?  If so, you likely plugged in a 2A3 without paying attention to the fat vs. skinny pins, which will destroy one of those resistors and leave you with dead voltages on one side (or both if you are unlucky and force both 2A3 tubes into the sockets the wrong way). 

As always, it's also a good idea to post build photos along with stuff like this. 

-PB

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline SamJ

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Reply #2 on: July 11, 2025, 05:10:14 AM
PB,

I'll check that and get some photos up as well.  I don't THINK i had the 2A3s installed incorrectly, but there's alway a chance there. 

Thanks for the quick response!

Sam


Offline SamJ

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Reply #3 on: July 11, 2025, 05:31:50 AM
The 130 ohm 2w resistor between 31 and 34 is reading either open or sometimes something really low like 1.9 (tough to get the leads in there), so looks to be bad.


Offline Paul Birkeland

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Reply #4 on: July 12, 2025, 03:03:16 PM
I don't see anything obvious.  I'd snag some replacement 130 ohm 2W resistors from us or online, then attempt to fire up the amp again once that open resistor is replaced.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline SamJ

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Reply #5 on: July 14, 2025, 04:20:39 AM
On it!  Will report back. 


Offline SamJ

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Reply #6 on: Yesterday at 10:26:17 AM
Swapped out the bad resistor, everything checks as per the instructions EXCEPT 14 is reading 391 (vs. 170-230) and the LEDs for the right channel are still not illuminated.  I reflowed all the connections on the PC board for that channel, and I THINK they all look good (I watched Doc's video on the subject).  The board is looking kinda rough with all the work I did on it, maybe I just start over with a new board?  Or re-re-reflow connections and try again? 

Sam


Offline SamJ

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Reply #7 on: Yesterday at 10:44:41 AM
Forgot pics...


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