Can I please get some direction figuring out how I broke the shunt regulator?

[zachengland]

I am editing my original post because I re-worked the solder joints and now have a different problem. I have taken photos but the forum is not allowing me to post external links.


I have completed the kit assembly.  When I went through the first time the shunt regulator board tested with the correct 220v on both sides.

Then on the last step in the manual when I was installing the heat sinks I broke one of the legs of the transistor on the A side.  I had to re-solder it with the bottom of the leg attached to the top pad of the board.  When I had the board removed I also replaced all black, white and red wires that connect to it with longer pieces because I was having a hard time re-connecting them in the tight space.

Somewhere, either in the operation to fix the transistor or to solder in longer connecting wires I broke something because now I am getting 140v on A and 307 on B.  I've verified all the connection points multiple times and cannot see any solder bridges either on the board or the tube socket.  I've also verified all the wires on the underside of the board that none came dislodged.

I get correct 214 v on the A side (the side I repaired) but I get 150v on the B side.  I re-checked the connections and believe they are correct.  I found another thread describing a similar problem that mentioned solder bridges on the transistors but I do not believe this is my problem.

I'm stuck at this point.  Can someone pleas advise which joints or components I should give another look?


I'm tempted to ask Bottlehead to sell me a new board and new transistors at this point.  These solder pads are tiny and re-work on these boards is difficult.

Edit to add: my input is 360 VDC.

[Paul Birkeland]

I would just replace the whole board if you're open to doing that. Also ensure that the Kreg connections go to their proper places, as this can cause the regulated voltages to get pretty whacky as well.

[zachengland]

How do I get a new board and transistors?

[Paul Birkeland]

replacementparts(at)bottlehead(dot)com.

[zachengland]

Sounds good, but before I go down that road can I give you some voltages and have you tell me if you think the likelihood is that the fault is in the board?  If it's not clear the fault is in the board I'd like to talk to you about shipping the whole kit to you and have you correct and finish the testing.

Here is what I currently have.  There may be some slight variation from the last measurements due to my variac and some fluctuation in my local AC:

a side:
147 vdc a the transistor body
2.2 vdc at the kreg point
212 vdc at the breg point

b side:
215 vdc at the transistor body
8.8 vdc at the kreg point
147 vdc at the breg point

My 275+ is 304 at this point

Further thoughts?

Thank you.

[Paul Birkeland]

It could just be a shorted 431 regulator.

Buying a new regulator board and installing it will take a lot less time and money than sending the kit my way.