Bad voltage at C4S board

[kjwcb2]

Hi! I have a reading of 124.9DCV at 1A on the C4S board. 1B is fine at 220.2VDC.

Any clue what might be causing this? Presumably an issue with the shunt regulator board.

[Paul Birkeland]

Is this an Eros 1 or Eros 2?  Is this the board above the D socket?

[kjwcb2]

It's an Eros 2. Yes, it's above the D scoket.

[Paul Birkeland]

IA and IB are wired together with a piece of wire.

Either your piece of wire is broken, or it isn't connected between those terminals.

[kjwcb2]

I've got the jumper between 1A and 1B. It seems to be fine, but I'll replace it anyway and see what happens.

[Paul Birkeland]

You can't have a wire between IA and IB and have a difference in voltage of 100+ V.  The wire has to be broken, out of place, or poorly soldered.

[kjwcb2]

Hi, I replaced the wire between 1A and 1B. No real difference. The readings now are: 1A - 148VDC / 1B - 214VDC. A 65VDC difference +/-
Interestingly, the reading at the MJE5731A transistor next to 1A is 219.8VDC, compared with 152VDC at the MJE5731A next to 1B.

[Paul Birkeland]

You can't have a difference in voltage between IA and IB with a piece of wire connected.  This is a physical impossibility.  100V across a piece of wire like that would dissipate thousands of watts and the copper would evaporate and possibly explode loudly in the process (though the power transformer wouldn't support this).

Can you post some build photos?

[kjwcb2]

What photos would you like?

[Paul Birkeland]

The top and bottom of the C4S board above the D socket.

[kjwcb2]

Here they are.

[kjwcb2]

Are they clear enough? I removed the heatsinks to test the transistor voltages. The board is a bit messy in places from all the soldering and desoldering.

[Paul Birkeland]

What type of solder are you using, what wattage is your soldering iron (is it adjustable), and are you using any additional flux or anything? 

What DC resistance do you get between OA and OB with your meter? 

[kjwcb2]

I'm using the best solder I can find locally. I don't think it's anything special but I've made 3-4 amp builds with it without any problem. I've got a Hakko soldering station - adjustable - set at 250 degrees.
The resistance between OA and OB is 441.4 KΩ. DC = 0.

[kjwcb2]

That's with the board disconnected.
Sorry for spoiling your Sunday!