Zero OA Voltage D side [resolved]

BenjaminSmith · 1470

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Offline BenjaminSmith

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on: April 22, 2022, 12:43:13 PM
Issue:  0.0 OA voltage, D side. 530V on IA. No B side LEDs lit.  Zero voltage on 46U. Kreg 0.08V A side, 0.9V B side. Amp has passed all previous tests.  Help, please!
« Last Edit: April 29, 2022, 04:20:30 PM by Paul Birkeland »

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Offline Paul Birkeland

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Reply #1 on: April 22, 2022, 04:53:46 PM
I would reflow all the joints on that PC board other than the ones where LEDs attach.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline BenjaminSmith

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Reply #2 on: April 24, 2022, 08:11:19 AM
Paul,

All joints checked and reflowed.  Still dead.  I neglected to mention that I had initially connected the 26U black wire to +reg instead of -reg (now corrected), possibly leading to the vaporized LEDS.

Toys in no particular order:
1975 BMW 2002
Sony A7RIII
Martin Logan SL3/Meridian transport/Bel Canto DAC & power
Cain&Cain Abbys S/Ns 001 and 002


Offline Paul Birkeland

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Reply #3 on: April 24, 2022, 08:18:14 AM
I did not notice the vaporized LEDs.  You'll want to replace that entire C4S board with a fresh one.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline BenjaminSmith

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Reply #4 on: April 24, 2022, 01:13:41 PM
Probably because I neglected to post this pic  :-[

Toys in no particular order:
1975 BMW 2002
Sony A7RIII
Martin Logan SL3/Meridian transport/Bel Canto DAC & power
Cain&Cain Abbys S/Ns 001 and 002


Offline BenjaminSmith

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Reply #5 on: April 28, 2022, 03:30:27 PM
The new board arrived, went together and was installed.  It works perfectly.  Now the issue is with the A side board which was just fine previously. IA measures 530V per manual. OA also reads 530V, not 300V. Terminal 32U was measured as it did before the D side board went in, adjusted and stable at 175V. The LEDS on A side of A socket board do not light (the B side light as they should) whereas on the opposite D side all four light appropriately.

Toys in no particular order:
1975 BMW 2002
Sony A7RIII
Martin Logan SL3/Meridian transport/Bel Canto DAC & power
Cain&Cain Abbys S/Ns 001 and 002


Offline Paul Birkeland

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Reply #6 on: April 29, 2022, 04:19:50 AM
A board that works and suddenly doesn't work will generally do so from flaky solder joints.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline BenjaminSmith

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Reply #7 on: April 29, 2022, 04:15:54 PM
Issue resolved.  Red wire from D4 to OA was busted directly underneath board. I've had trouble with solid core wires breaking after repeated movement - I may be scoring the wire as I strip the insulation.

Anyways, thank you Paul. I should be listening to sweet music in an hour or so!

Toys in no particular order:
1975 BMW 2002
Sony A7RIII
Martin Logan SL3/Meridian transport/Bel Canto DAC & power
Cain&Cain Abbys S/Ns 001 and 002