Shunt regulator readings [resolved]

[PS2500]

The X pad reads 2.72V on the B half of the board, and 2.48 on the A half. The multimeter settled rock steady on those two values.

[Paul Birkeland]

Would it be possible to see some bottom photos of that shunt regulator board? 

[Paul Birkeland]

Another thing you might also try is wiring D2 to D7.  If one of the resistors that is responsible for grounding the grids isn't doing its job, tying them together will ensure that neither grid can drift up past ground potential.

[PS2500]

Another thing you might also try is wiring D2 to D7.  If one of the resistors that is responsible for grounding the grids isn't doing its job, tying them together will ensure that neither grid can drift up past ground potential.

I take it you mean just running a wire between those two terminals and soldering them in? And doesn't need to be insulated?

Would it be possible to see some bottom photos of that shunt regulator board?

Damn. Wish I'd taken the shot when I had the board off. Sure, I can get a photo, but I'll need to remove a few wires and take the board off again. It might be a week or so before I can get to that.

In the meantime, I really appreciate the time and trouble you've put in to help out with this.

[Paul Birkeland]

Yes, just connect D2 and D7 with a piece of wire.

[PS2500]

I've connected D7 and D2 to each other by wire, rerun the test, and I still get 144 VDC on the D2 wire.

I can get the shunt board off and photograph the underside for you, but if it's what it takes to get rid of this issue, I'm about ready to order a new board and put all new components onto it.

[Paul Birkeland]

Putting a new board with new components on it may or may not resolve your issue.  If you can take the board off and photograph the bottom, then also photograph the D socket, that could be helpful.

[PS2500]

Putting a new board with new components on it may or may not resolve your issue.  If you can take the board off and photograph the bottom, then also photograph the D socket, that could be helpful.

If I can do that before the weekend runs out, I will. Don't laugh at my soldering. I'm also going to retest the power supply board, just to confirm that I have the right readings from there.

I will just mention that, as I said several posts ago, I resoldered the D socket connections, including reinstalling the resistors, to see if it helped. The only one that I left in place at that time was the STP from the C socket.

I have looked at the C socket itself and all connections there seem to be as specified. I will put up a photo of that as well. Also, just to be sure, I disconnected the black wires at the T23 end, trimmed and restripped the ends, and soldered them back in place.

This process has been a little frustrating, because I don't feel great about heating some of the connection points or component leads multiple times or for too long. Also, I have broken connections sometimes when bending wires out of the way (broken off the end of the wire) - where practical, I have been disconnecting them in preference to bending them.

[PS2500]

Also, I assume this is nothing, but could you take a look at the 2N2907A transistors? They're visible in the "shunt4.jpg" photo I posted on June 16th. The case of the transistor on the left (A-side) is pretty corroded. I'm assuming it's not a problem - can you confirm that?
(The thing that looks like a bead of moisture was just some dried adhesive or something - I've already removed it.)

[Paul Birkeland]

Some corrosion on the metal case of a 2N2907 isn't particularly concerning. 

[PS2500]

Hi Paul,

Here are some photos of the underside of the board. This is the best I can do without taking the whole thing off. I'm nervous both about yanking the board around while in place, and about soldering and resoldering the same locations. Things are getting a bit more raggedy than when I first finished soldering up this board.

These are all with the B side of the board on the left of the picture. There's a detail of the far corner because I didn't think the original shots showed it clearly enough.

I also included a shot of the C socket.

[Paul Birkeland]

Can you get one in focus of the D socket itself? 

Where did the white wire come from, and what's it being substituted for?

[PS2500]

Where did the white wire come from

Sorry, I had intended to mention that yesterday, and it slipped my mind. At the risk of answering too literally, it came from a Crack kit, left over from a build I did a few years ago. The white wire was handy as a contrast to the red and black wires that the Eros uses.

The terminal was getting crowded and difficult to work with, and more than once now as I've spent more and more time on redoing bits on that board or parts of that socket section, I've nicked things with the soldering iron. No damage beyond cosmetic, but it feels bad and it looks bad. So to run the wire from D2 to D7 as you suggested, I attached it round the outside of the socket instead of crossing through it. It's not that I'm not going to know which wire I used, but the white makes it conspicuous as I figured I'd be removing it later if it didn't test out. And as I mentioned a couple of posts back, unfortunately the tests were the same as the previous results.

I'll try and get photos of the D socket up tonight.

[PS2500]

Here are some photos of the D socket. I've got a feeling you might be going to ask about the 4 and 5 pin, which may not be clearly visible in the pictures. I did check that connection when I first tested this section. It looked good. However, I also undid it and resoldered - I think I even cut new wire for that part. From having looked at those pins many times, and the wires and the solder joints, I believe those connections are not at fault.

These shots are from various angles, as you can see from the numbering, but I couldn't get around by D4/D5 while the shunt board is still attached.

[Paul Birkeland]

Ah, I see now that it's your D2 to D7 jumper.

I know this isn't the most helpful suggestion, but honestly I would go back over each individual step in building and installing that PC board.  Most of the resistors on it can be measured after they are installed, so you can check them.  Also pay very, very close attention to where the wires go from each individual solder pad on that PC board down to the D socket.  You are correct that there are many wires of the same color, and we have added blue and white wires to the Eros 2 (not yet available for tape) to help with this situation.

If all else fails, I would suggest sending it in for repair.

-PB