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January 30, 2023, 07:43:47 PM

Author Topic: First startup ... Pls Help!  (Read 928 times)

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Offline mlineHK

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Re: First startup ... Pls Help!
« Reply #30 on: March 26, 2022, 08:00:53 PM »
hi Paul,

these r the results after re-solder every contact on all 3 boards.


IA A and B 274v
6.3 57v
-6.3 52v
275 275v
Biasing 1.45v


Breg A 273v
Breg B 216v
Kreg A 1.18v
Kreg B 10.66v
OA 1.76v
OB 2.02v
« Last Edit: March 26, 2022, 09:47:09 PM by mlineHK »

Offline Paul Birkeland

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Re: First startup ... Pls Help!
« Reply #31 on: March 27, 2022, 05:40:09 AM »
Resoldering your connections brought one side into proper operation.  I would suggest that you also resolder the center PC board and perhaps that will fix the other side.
Paul "PB" Birkeland

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Offline mlineHK

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Re: First startup ... Pls Help!
« Reply #32 on: March 27, 2022, 06:13:52 AM »
That's what I thot and I have done re soldering the middle board as well. I will redo again and see. 

Offline Paul Birkeland

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Re: First startup ... Pls Help!
« Reply #33 on: March 27, 2022, 06:15:51 AM »
You could also replace the 431 regulator on the side with the very low Kreg voltage.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline mlineHK

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Re: First startup ... Pls Help!
« Reply #34 on: March 27, 2022, 07:05:16 AM »
Thank you Paul will try to replace them.

Offline Paul Birkeland

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Re: First startup ... Pls Help!
« Reply #35 on: March 27, 2022, 07:19:28 AM »
Thank you Paul will try to replace them.
It, you definitely don't want/need to replace the working one.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline mlineHK

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Re: First startup ... Pls Help!
« Reply #36 on: March 27, 2022, 07:34:16 AM »
Yes will replace the a side one.

Offline mlineHK

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Re: First startup ... Pls Help!
« Reply #37 on: April 04, 2022, 07:25:33 PM »
hi Paul,

after replacing the A side LM431ACZ ,  the results remain unchanged.  what do u suggest I shall do next?

Offline Paul Birkeland

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Re: First startup ... Pls Help!
« Reply #38 on: April 05, 2022, 04:23:46 AM »
Have you reflowed all of the solder joints in the amp?
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline mlineHK

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Re: First startup ... Pls Help!
« Reply #39 on: April 05, 2022, 04:47:24 AM »
All joints on 3 boards only.

Offline Paul Birkeland

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Re: First startup ... Pls Help!
« Reply #40 on: April 05, 2022, 05:10:03 AM »
I would go over the 12AU7 socket and associated terminal strips as well.
Paul "PB" Birkeland

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Offline mlineHK

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Re: First startup ... Pls Help!
« Reply #41 on: April 05, 2022, 05:15:10 AM »
ok will do thanks.