Eros - Shunt Regulator Voltage Test

[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!

 

[Paul Birkeland]

Yes, I would go ahead and solder that connection.

-PB

 

[onion_breath]

Okay. Well I soldered the drain wire at center pin on D and also replaced the broken cable and checked all the other cables for cold joints. I also did as Doc B suggested and checked for continuity on the tube socket terminals at D1 and D6. My results are still very low readings  - comparable to my first measurements on D1 and D6. This time around my results were 4.8 VDC on D1 and 3.2 VDC on D6.

 

[Paul Birkeland]

What voltages do you see at OA and OB now?

 

[onion_breath]

OA - 3.02 VDC
OB - 4.81 VDC

 

[Paul Birkeland]

I think at this point that your best bet is to send your Eros in for repair and we can figure out what's going on for you.

-PB