LED not lighting and weird DC readings. [resolved]

dotashope · 1498

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Offline dotashope

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on: November 07, 2020, 09:17:56 AM
Aight so I finished the kit last night, passed the resistance test. And this morning I got some strange readings on DC voltages. Here's what I got, and a pic of the wirings. Also the 2 caps on 6,7 and 9,10 are running hot. I don't know if it's from the tube or not.
1. -90mw
2. -125mw
3. 0
4. -97mw
5. -82mw
6. 0
7. 179w
8. 0
9. 59w
10. 0
« Last Edit: November 08, 2020, 03:21:18 PM by Paul Birkeland »



Offline Paul Birkeland

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Reply #1 on: November 07, 2020, 10:45:32 AM
I see at least one wire poking out at terminal 12 that's not trimmed.  You need to trim that and any others like it.

Do your tubes glow?

Is your meter set to AC or DC voltage?  What happens if you try to measure the voltage of a 9V battery? 

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline dotashope

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Reply #2 on: November 07, 2020, 11:28:34 AM
Ye I trim all the leads, the on you see on 12U is for the alligator clips. I couldn't get a solid clip on 12U so I just added a little wire to clip on. I'm sure that I was measuring DC voltage, got a 1.5V battery around and got 1.31 reading out of it. Throughout the build I've never bump into this level of confusion tbh... It went really smooth until last step :/



Offline Paul Birkeland

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Reply #3 on: November 07, 2020, 11:31:27 AM
You have a miswire on the octal socket.  B2 and B5 need to be connected.  The capacitor at T6/T7 has been exposed to voltages above its ratings, so once you get the amp up and running I would recommend ordering a replacement.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline dotashope

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Reply #4 on: November 07, 2020, 12:47:35 PM
Awww man how did I miss that... Sorry for your time :/ I'll fix it and report back. Thank you so much!



Offline Paul Birkeland

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Reply #5 on: November 07, 2020, 03:12:55 PM
Awww man how did I miss that... Sorry for your time :/ I'll fix it and report back. Thank you so much!
There's certainly no need to apologize, this is exactly the purpose of this forum.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline dotashope

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Reply #6 on: November 07, 2020, 03:37:05 PM
There's certainly no need to apologize, this is exactly the purpose of this forum.
Thanks a lot! It was exactly the problem. The LEDs are working and below is the DC voltage. Very keen eyes.. That miswiring totally slipped during the visual check. Now I'm just waiting for the amp to cool down and do some listening test. Thanks again :D

1. 82.6
2. 178
3. 0
4. 178
5. 88.9
6. 0
7. 108
8. 0
9. 111.5
10. 0



Offline dotashope

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Reply #7 on: November 07, 2020, 05:21:15 PM
There's certainly no need to apologize, this is exactly the purpose of this forum.
The listening result is fine, great really. Plenty of bass. Btw is it a good idea to leave the amp on without a load? Cuz I think I heard popping sounds when plugging in.



Offline Paul Birkeland

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Reply #8 on: November 07, 2020, 05:47:55 PM
You can leave the amp on without a load.

If you have popping sounds while the amp is running, that suggests that there are loose solder joints in the amp.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline dotashope

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Reply #9 on: November 08, 2020, 09:33:31 AM
Thanks for confirming! I did another visual check and did find a terminal on headphone socket that I forgot to solder. After that the occasional static is gone. It's functioning as it should. And I measured the dc offset with a trs cable, it gets really jumpy even after a couple minutes. Mainly around 0-20mw, sometimes -10mw. It didn't mention in the manual but is it within the recommended range? Thanks!



Offline Paul Birkeland

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Reply #10 on: November 08, 2020, 10:40:18 AM
0.01-0.02V is plenty close to 0V.  Most meters don't resolve DC voltages that low very well anyway.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline dotashope

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Reply #11 on: November 08, 2020, 01:57:18 PM
Well it seems like I'm good to go, gonna give the amp some time then add the speedball in. Thank you so much for helping me out! Couldn't've done it without your help :D