Eros - Shunt Regulator Voltage Test

[onion_breath]

Checked the 431 slot which had 431's installed properly. Pulled the 12BH7 and measured IA and OA. IA read: 352.2 VDC ; OA read: 4.78 VDC.

[onion_breath]

If there are any other measurements needed to help troubleshoot, or anything else recommended please let me know.

I'll just be putting the build on hold in the meantime.

[Doc B.]

Are all of the jumpers on the board showing good continuity from pad to pad?

[Paul Birkeland]

Remove the red wire from OA that connects to the tube socket.  Also remove the red wire from OB that connects to the tube socket.

Now recheck OA and OB.

-PB

[onion_breath]

I removed the red cable from both OA and OB.

OA : 4.79 VDC
OB : 4.89 VDC

I also remeasured IA and IB.

IA : 360 VDC
IB : 360 VDC

I'll see what recommendations you have, and will try to work on more troubleshooting tonight.

[Paul Birkeland]

Remove the other red jumpers on OA and OB, then remeasure OA and OB.

-PB

[onion_breath]

Finally got a chance to remove the other OA and OB jumpers.

OA : 219.8 VDC
OB : 222.3 VDC


I'm getting nervous this troubleshooting will never end

[Paul Birkeland]

Well, this tells us that the C4S bits of the PC board are OK (the center bits with the MJE5731A/2N2907 and LED's).

When you have the OA/OB bits jumpered to the outsides of the board, your voltages are sinking like crazy.  You've checked the placement of the individual parts, but I'd wonder if there's an issue with the way the board is wired to the tube socket.  If the OA and OB pads aren't connected to D1 and D6, but rather to D3 and D8, I could see you getting this problem. 

-PB

[onion_breath]

I double checked the OA and OB pads, which were properly connected to D1 and D6. I am tempted to just reattach the pads to OA and OB, but before doing so should I check for anything else? Otherwise I can reattach and send you measurements of the results.

BTW - as I was assembling and now disassembling, I've noticed that the wires (specifically the red wire used for this kit) seem to be breaking, like they're somewhat brittle. Is this a normality I should be seeing with cable that have a relatively small gauge?

[Doc B.]

If the wires are breaking right at the insulation it is an indication that your stripper is set too tight and nicking the wire itself, creating a stress point. If it's just breaking in random places it's because its getting work hardened from too much bending and flexing.

[onion_breath]

Well Doc & PB - any more input on possible next steps?

[Doc B.]

Have you checked all the wires connecting to the board for continuity?

[onion_breath]

I have not. What's your best recommendation for checking continuity? And just to be clear - are you referring to just the Shunt Regulator board, or both Shunt Regulator board and PSU board?

[Doc B.]

You want to be sure to put the probes 'outside' of the wire connections so you don't accidentally test in such a way that you are leaving out a broken part of the wire or a cold joint within the span of the ohmmeter probes. In the case of a PC board attached to a tube socket you want one test lead on the pad the wire is attached to on the board rather than touching the end of the wire itself, and at the other end you want the other probe touching the tube socket terminal rather than the wire end attached to it.

[onion_breath]

So this project has been on the back burner for some time and I'm just getting some time now to get back into it. I was checking some wires on the Shunt Regulator board and noticed the wire that connects from D3 to the Kerg B pad was broken. In the process of replacing that I noticed that the drain wire on the 6" STP cable that connects from the C socket to the D socket was never soldered in the center pin of D. I reread the directions and there is no comment on having that soldered between attaching the cable and conducting the Shunt Regulator Voltage test. Do you think this could have caused the problem for the readings? And if so is there an issue if I solder that wire now? I was working through the manual and see no more connections going to the center pin of D.

Thanks!