Eros phono final voltage test fail [resolved]

Nitsua08 · 1814

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Offline Nitsua08

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on: February 09, 2024, 06:12:09 PM
Hello, I am trying to sort out some failing numbers on my voltage readouts on the C4s board. Here are my numbers:
IA = 218
IB = 219
OA = 163
OB = 138 (low)
OC= 97
OD = 126 (high)
OkA=98
OkB=125 (high)
OkC=1.6
OkD=3.0 (high)

Thanks
« Last Edit: April 08, 2024, 05:53:22 AM by Paul Birkeland »



Offline Paul Birkeland

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Reply #1 on: February 10, 2024, 06:02:36 AM
For something like this, it's helpful to post build photos.  Deviations like these are often cold solder joints, especially on the Q2 transistors on that center C4S board, but also sometimes around the 9 pin sockets. Occasionally something like a swapped R1 resistor can also cause similar problems.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Nitsua08

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Reply #2 on: February 10, 2024, 09:17:57 AM
Thanks for the reply, Paul. I ended up removing the board and re-soldering all of the socket pins and anything else that looked questionable. After retesting, the voltage numbers are the exact same. I think the soldering looks OK on the Q2 transistors but I'm pretty new to this too. Anyways, i've attached some photos.



Offline Paul Birkeland

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Reply #3 on: February 10, 2024, 01:37:23 PM
Can I see the bottom of that forward C4S board?

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Nitsua08

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Reply #4 on: February 10, 2024, 03:29:12 PM
Sure thing.



Offline Paul Birkeland

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Reply #5 on: February 11, 2024, 07:21:39 AM
That's the kind of solder joint that you have to look out for. 

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Nitsua08

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Reply #6 on: February 11, 2024, 08:33:55 AM
Hmmm. I ended up resoldering most of that side of the board and am still getting high voltages, even a little higher in OkD:
IB = 219
OB = 146 (low)
OD = 141 (high)
OkB=141 (high)
OkD=5.0 (high)



Offline Paul Birkeland

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Reply #7 on: February 11, 2024, 09:35:45 AM
The pattern of damage on the Eros 2 kits that I repair is usually that there's a solder joint problem on the C4S board, the amp is run, the 2N2222 is damaged in the process, then the solder joints are fixed and the 2N2222 has to be replaced.  I would try this next.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Nitsua08

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Reply #8 on: February 11, 2024, 10:06:33 AM
Ok, so I should order a new 2N2222A transistor? Looks like these can be found on Digikey or Jameco. Should I order any other parts like a MJE350 to see if that is the issue?

Again, thank you for your help on this.



Offline Paul Birkeland

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Reply #9 on: February 11, 2024, 03:05:05 PM
I would just try one new 2N2222.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Nitsua08

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Reply #10 on: February 14, 2024, 01:44:49 PM
After adding a new 2N2222A, I’m still not getting the correct voltages:
IB = 220
OB = 136
OD = 127
OkB=127
OkD=3.0

Slight improvement but basically back to the original numbers.



Offline Paul Birkeland

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Reply #11 on: February 15, 2024, 04:24:37 PM
Can I see what the build looks like with that front C4S board removed?

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Nitsua08

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Reply #12 on: February 15, 2024, 04:38:35 PM
Sure thing.



Offline Paul Birkeland

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Reply #13 on: February 16, 2024, 01:53:46 PM
I would try popping in a different 6922.  It has also been my experience repairing these that problematic solder joints can lead to situations that are unkind to the 6922.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Nitsua08

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Reply #14 on: February 16, 2024, 02:01:30 PM
Is that something I can purchase from Bottlehead?