Eros 2 Phono C4S Voltage Check

nadamp · 2369

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Offline nadamp

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on: May 20, 2020, 04:02:39 AM
Hey Folks, got everything soldered up and going through the Voltage Check on page 76. The IB side of the board looks to be having acceptable voltage levels, but the IA is another story.  When measuring the IA side of the board my meter fluctuates from low to high and then overload for OC, OkA, and OkC.  I've checked the wiring and it seems *ok* to me but I've attached a few pictures in hopes that you all can spot something I'm not! I'm using a Fluke 87 V if there are particular modes you want me to check with.

Voltages:
------------
IA  217V
IB  217V
OA  216V
OB  164V
OC  ????
OD   95V
OkA ????
OkB  97V
OkC ????
OkD 1.4V


Offline nadamp

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Reply #1 on: May 20, 2020, 04:03:37 AM
A few more shots


Offline nadamp

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Reply #2 on: May 20, 2020, 04:05:11 AM
And one last one


Deke609

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Reply #3 on: May 20, 2020, 04:34:20 AM
The easiest approach might be to remove the board and reflow all of the joints on the offending side, with particular attention to the middle legs of the rectangular black ICs.

cheers, Derek


Offline Paul Birkeland

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Reply #4 on: May 20, 2020, 05:07:43 AM
Your meter should stabilize on a DC voltage if you leave the probe on a given terminal for 5-10 seconds. 

I would definitely pop the wires off of one side of the board, tilt it up, then reflow most of the joints on the board.  I would reflow every solder joint other than the HLMP6000 diodes, as those solder very easily.  I can see that your MJE350s aren't all that well soldered because the solder hasn't flowed through to the top side of the board.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline nadamp

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Reply #5 on: May 20, 2020, 06:15:24 PM
Derek and Paul,
Thanks for the guidance. I took your advice and unsoldered the wires on half the board and reflowed all joints. updated voltages:

Old:         New:
-----------------
IA  217V     218V
IB  217V     218V
OA  216V    216V
OB  164V    163V
OC  ????     ???  (fluctuates and ends with OL)
OD   95V      96V
OkA ????      ???  (fluctuates and ends with OL)
OkB  97V      98V
OkC ????     3.8V (fluctuates between 2.7 and 3.8, seemingly really high)
OkD 1.4V    1.4V


Offline nadamp

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Reply #6 on: May 20, 2020, 06:16:04 PM
Thanks for the help folks, not sure what I'm missing here..


Offline Paul Birkeland

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Reply #7 on: May 21, 2020, 05:55:39 AM
If you can't get voltage measurements at those terminals, you can send it in for flat rate repair.  Otherwise I would suggest going over the build step by step to see if anything has been missed.  You could also try a different meter.   

Not knowing what those actual voltages are on the rest of those terminals, I can't make any suggestions regarding what might be going on.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline grufti

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Reply #8 on: May 21, 2020, 06:37:04 AM
Redo the soldering on the two red wires at OA and OC and at the white wire next to those two. Make sure the solder actually reflows.


Offline Doc B.

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Reply #9 on: May 21, 2020, 06:43:35 AM
This might be a case of one of the wires attaching the board being broken inside the insulation and making intermittent contact.

Dan "Doc B." Schmalle
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Bottlehead Corp.

Offline nadamp

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Reply #10 on: May 22, 2020, 05:05:19 PM
I un-soldered all wires going to the c4s board,.. and reflowed *every* joint.  I replaced *all* the wires (1 black, 4 blue, 2 red, 2 white) Put everything back together and I'm still seeing volt fluctuations on the IA side of the board.  All LEDs on the shunt regulator are solid red.  Something that I was able to capture with all the lights off is that D1A and D2A glow and then dim out in unison in a loop.  I captured the behavior on video here:



Offline Paul Birkeland

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Reply #11 on: May 22, 2020, 05:29:15 PM
That would have me looking for a loose connection in the build. It may be a loose component one one of the front 3 9 pin sockets or terminal strips close by.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline nadamp

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Reply #12 on: May 23, 2020, 11:21:21 AM
I was just thinking, if I want to isolate that it’s a board component or a particular socket in a channel... could I desolder all wires from the c4s and wire the wires on the ib side (where all values were acceptable) and solder them to their appropriate counter part holes on the ia side? That would at least remove one socket out of three that may be causing my troubles?


Offline Paul Birkeland

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Reply #13 on: May 23, 2020, 03:39:06 PM
Yes, you could give that a try.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline nadamp

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Reply #14 on: May 24, 2020, 12:39:31 PM
After wiring the wires that would normally go to the ib side to the ia side.. all points measure fine. So it looks like it isn’t a board component.

After eyeballing everything once more I found that the capacitor for from the right channel wasn’t soldered to 21L. After resoldering all the wires to the side of the board they are supposed to be and reflowing the capacitor solder joint I have more stable readings, albeit strange:

IA  218
OA  215
OC  211
OkA ???
OkC 6.91

Any tips/tricks?


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