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[Amps] SB-220 HV meter on zero

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Subject: [Amps] SB-220 HV meter on zero
From: Catherine James <>
Reply-to: Catherine James <>
Date: Tue, 1 Nov 2016 00:08:28 +0000 (UTC)
List-post: <">>
I have replaced the back-to-back meter diodes on the Harbach diode meter board 
(which came with the amp pre-installed, and is not the latest version), 
replaced the capacitor block, installed a 10 ohm Ohmite glitch resistor, 
reassembled the amp, and powered up for the first time.

Meter lights come on, fan comes on, tube filaments light up brightly.  But the 
meters remain stuck on zero.  With the switch set to HV, both meters read zero. 
I am not expecting to see grid/plate current, but I certainly expect to see a 
solid HV reading.

I don't know if I have a meter problem, a resistor problem, or an actual lack 
of HV.  I am particularly concerned because it's difficult to know if the 
capacitors are fully discharged before opening the case when you have no HV 
meter reading.  My guess is that it's either the meter(s) or a resistor/diode 
problem (though I checked all the diodes on the meter board before 
reassembling) rather than an HV problem.  Is there any easy way to test this 
with the power off?

I haven't tried to key up the relay or push RF through it.

Thoughts on next steps?  I'm pretty confident the bleeder resistors will drain 
the caps since all of the caps and resistors in the power supply section are 
new.  I am **not** particularly eager to do any work with the case open and the 
240V power plugged in, much less powered up.

If anyone has a schematic for the metering circuit, not just the meter/diode 
board but including the meters, that would be helpful.  It's difficult to trace 
circuits from the Heathkit pictorial manual without a schematic.


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