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[AMPS] Follow Up on the SB-220 Follow UP

To: <amps@contesting.com>
Subject: [AMPS] Follow Up on the SB-220 Follow UP
From: km1h@juno.com (km1h@juno.com)
Date: Fri, 19 Mar 1999 00:10:22 -0500


On Thu, 18 Mar 1999 23:17:06 -0500 "Walter Fairclough"
<wfairclo@netcom.ca> writes:
>
>Further testing indicates only the 0.82 ohm resistor blew. I replaced 
>it
>with Harbach supplied 0.82 3W WW. Turned amp on, everything appears 
>normal
>unkeyed. Keyed, the resting plate current now reads 160ma, down from 
>210ma
>before bang. Don't know why. I could try shorting out another bias 
>diode to
>bring it up to 200-230ma or is 160ma OK. This would make 2 diodes 
>shorted
>out of the existing 8.


That idle current is trying to tell you something. Stop, think and look.

Is the HV really OK?
What is the idle current, one tube at a time.
Something is not correct here.

>
>Suppressor resistors measure 30 ohms on both tube anodes. Don't know 
>what
>they were before but 30 ohms seem reasonable.


They have no bearing on the problem anyway.

73  Carl  KM1H

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