[Top] [All Lists]

[Amps] SB-220 saga continues

To: <>
Subject: [Amps] SB-220 saga continues
From: Catherine James <>
Reply-to: Catherine James <>
Date: Thu, 3 Nov 2016 12:39:51 +0000 (UTC)
List-post: <">>
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 
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>


Amps mailing list

<Prev in Thread] Current Thread [Next in Thread>
  • [Amps] SB-220 saga continues, Catherine James <=