Kaiju driver board D potentiometer not changing 46U voltage [resolved]

[Pandymonium]

Today I tested the Kaiju driver boards. Board A checked out. Board D checked out for IA (514V) and OA (298V), but turning the pot did not change the measured voltage at 46U, which measured a steady 296V.

I removed the board to check solder joints and parts/connections. I didn't find any problems, although I am going to redo the solder joints just to make sure. I also confirmed that the pot is working by measuring the changing resistance between the outer pins after a few turns.

Before I proceed, does anyone have any thoughts on the problem I'm having? Is there a particular spot or part on the board that I should be focusing on?

Thanks for your help.

 

[Paul Birkeland]

When you see the OB voltage (which does go to 46U) remaining at about the IB voltage (which is wired to OA), the most common issue is that the center leg of the MJE5731A transistor on the B side hasn't gotten adequate heat from your soldering iron, and no current is flowing.

You'd want to also double check what the Kreg voltages are adjacent to that little trim pot on each end of the full rotation, which is 10 turns. You could have some odd problem with jumpers or the configuration of the PC board not allowing the cathode to be properly biased.

-PB

 

[Pandymonium]

That fixed it. Thank you Paul.