1A/1B reading 100v [resolved]

Brooklynbottle · 668

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Offline Brooklynbottle

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on: April 02, 2024, 12:06:08 PM
Just completed my Eros 2 build and ran through the resistance and voltage checks. Everything within spec except for 1A & 1B reading 100v.
I read through the forum and noted Paul's advice to look more closely at the regulator board (near Au7) and took the following readings:
OA/B 220v
AKREG 7.09
BKREG 7.06
A/B bregs 0
I examined my wiring and solders all look to be up to snuff.
Obviously something is up w/ the BREG voltage.
Many thanks in advance for guidance.
Addendum:
Is it possible that I fried my 431's? I accidentally installed the 220 ohm instead of the 220k ohm and powered up as recommended before I spotted the error and replaced w/ the correct resistor.
« Last Edit: April 11, 2024, 06:45:54 AM by Paul Birkeland »



Offline Brooklynbottle

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Reply #1 on: April 02, 2024, 03:00:11 PM
Here are the images of the board/Au7 socket in question.



Offline Brooklynbottle

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Reply #2 on: April 03, 2024, 01:53:59 AM
One last symptom to report. My EF 86's were warm, but not glowing (when viewed in a dark room).



Offline Paul Birkeland

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Reply #3 on: April 03, 2024, 06:35:26 AM
Just completed my Eros 2 build and ran through the resistance and voltage checks. Everything within spec except for 1A & 1B reading 100v.
Is this IA and IB on the regulator board over the D socket or on the PC board up front?

OA/B 220v
AKREG 7.09
BKREG 7.06
A/B bregs 0
 I accidentally installed the 220 ohm instead of the 220k ohm and powered up as recommended before I spotted the error and replaced w/ the correct resistor.
I'm super confused here.  The manual says to test the board above the D socket and not to proceed if those voltage checks don't pass, but you say you've completed the build so they must have passed at some point?

On the D socket PC board, OA/OB each connect to the breg pads with wire and allow the regulator to work to pull down the incoming B+ to 220V regulated.  You have an appropriate set of Kreg voltages and correct OA/OB voltages, so my suspicion would be that you should redo your Breg measurements.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Brooklynbottle

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Reply #4 on: April 03, 2024, 08:37:06 AM
Oh boy.
The reason you're confused is because I'm confused more!
I was checking
A1 and B1 at the A & B sockets! (Not on the board).
Everything checks out to spec as per the manual.
The only thing that's a bit odd is IA & IB read 259.8V (on two different meters).
Is this a cause for concern?
Thanks for the assist.



Offline Paul Birkeland

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Reply #5 on: April 03, 2024, 03:03:17 PM

The only thing that's a bit odd is IA & IB read 259.8V (on two different meters).
On the front board or the board above the D socket?

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Brooklynbottle

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Reply #6 on: April 03, 2024, 03:33:42 PM
The board above the d socket.



Offline Brooklynbottle

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Reply #7 on: April 03, 2024, 03:37:50 PM
Front board reads within spec for voltage
 



Offline Paul Birkeland

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Reply #8 on: April 04, 2024, 05:35:35 AM
My suspicion is that you just have AC powerline voltage that's slightly below nominal, but 5V of difference there isn't anything to stress over.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Brooklynbottle

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Reply #9 on: April 04, 2024, 09:57:41 AM
Got it. I'll connect the Eros and see how it goes!
Thanks much. Will report the results.



Offline Brooklynbottle

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Reply #10 on: April 04, 2024, 12:06:07 PM
So close!
My left channel is maybe 20% lower in level than the right.
Here are my readings:
1a 221.1
1b 219.5
OA 166
OB 163.3
OC 95.5
OD 96.6
OKa 96.6
OKb 97.5
OKc 1.53
OKd 1.32

Breg b 221
Kreg b 7.11
Breg a 219
Kreg a 7.11

Seems everything is within spec. Both sides of the Au7 are glowing.
Any ideas?
Thanks again!!!



Offline Brooklynbottle

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Reply #11 on: April 04, 2024, 12:09:02 PM
PS swapped cables with R channel remaining the same.



Offline Paul Birkeland

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Reply #12 on: April 04, 2024, 03:10:23 PM
I would let the Eros cook overnight to see if that changes anything.  If nothing changes, also try swapping the EF86s to see if the low level follows a tube.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Brooklynbottle

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Reply #13 on: April 04, 2024, 04:14:38 PM
Tube swap early on did not affect signal variation. However I suspect suspect "settling in" might be the key. Signal improved a bit with longer play. Thanks again! Will report results.



Offline Brooklynbottle

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Reply #14 on: April 05, 2024, 04:43:10 AM
The proverbial rabbit hole!
Conducted the following diagnostics:
Dropped to one interconnect to a/b compare Left & Right Eros OP channels.
Hooked up my old Mojo phono pre-amp to r/o channel imbalance from the phono cartridge (was OK)
Swapped a/b position tubes
Finally installed a rudimentary dB meter app which indicated an approximate 10dB deficit in the R channel. Confirming what I'm experiencing.
Seems the Fidelity is fine right channel just quieter.
Any ideas?
Thank you.