[Amps] SB-220 saga continues

Thu Nov 3 08:39:51 EDT 2016

Thanks to all who gave advice, links to documentation, etc.

The meter reads 1400 ohms when disconnected from the side meter board and connected to an ohmmeter, and that puts the meter at half scale. It's clearly good.
The diodes on the diode/meter board test as good, i.e. same resistance at DC as the new ones I bought and tested loose.
The wires between the diode board and the HV capacitor test as good.
The resistors in the voltage divider for the meter test as good.
The cap board is brand new from Harbach.  The diode/meter board is also Harbach, but came installed in the amp and is clearly not recent vintage, judging from the color of the PC board.

Everything I've tested so far with the ohmmeter suggests that it should work, but it doesn't. I am not world's greatest troubleshooter, and I'm running out of ideas for powered-down ohmmeter treats.

The only next step I can think of is to reassemble everything, defeat the interlock, power up with case open, and VERY CAREFULLY test voltage at B+/B- on the cap board (or on the bottom R/C and multiply by 4), the transformer secondary wires, and the orange wire meter board feed.  There should be ~3000V at B+/B-, and much less at the orange wire meter feed (will need to study voltage divider to see what to expect).

<head scratch>

Cathy
N5WVR