Eros phono final voltage test fail [resolved]

[Nitsua08]

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

 

[Paul Birkeland]

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.

 

[Nitsua08]

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.

 

[Paul Birkeland]

Can I see the bottom of that forward C4S board?

 

[Nitsua08]

Sure thing.

 

[Paul Birkeland]

That's the kind of solder joint that you have to look out for. 

 

[Nitsua08]

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)

 

[Paul Birkeland]

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.

 

[Nitsua08]

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.

 

[Paul Birkeland]

I would just try one new 2N2222.

 

[Nitsua08]

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.

 

[Paul Birkeland]

Can I see what the build looks like with that front C4S board removed?

 

[Nitsua08]

Sure thing.

 

[Paul Birkeland]

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.

 

[Nitsua08]

Is that something I can purchase from Bottlehead?

 

[Paul Birkeland]

Yes, you can reach out to replacementparts(at)Bottlehead(Dot)com to ask about a replacement.

 

[Nitsua08]

Well, I ordered a 6922 on Amazon so I could fiddle with it over the weekend. I put in a fresh 2N222 before running the test. Popped in the new 6922, and I’m still getting the same voltages.

 

[Paul Birkeland]

Can you show me what the bottom of the PC board looks like now?  If you swap EF86s between sides, do the problematic voltages move?

 

[Nitsua08]

I did try swapping the EF86 and it didn't make a difference. Here's a few updated photos. Tried to get the best light I could.

 

[Paul Birkeland]

Here's another example of a joint on that board that isn't soldered.

Please reheat all of the solder joints on this board that don't have LEDs poking through them.  You may again have to replace the 2N2222 transistor on that side.  I will reiterate that I have seen this exact same problem a few times and had to take these kits in on repair, and it is always flaky solder joints and a dead 2N2222 transistor, and occasionally the tubes will be damaged in the process depending on where the flaky joints are.