[Top] [All Lists]

Re: [Amps] SB220 Meter blown...follow up hope

Subject: Re: [Amps] SB220 Meter blown...follow up hope
From: Paul Kraemer <>
Date: Fri, 15 May 2020 14:12:57 -0500
List-post: <>
That will certainly test the meter movement!  It will pin hard once that then you will know it is bad.


Paul K0UYA

On 5/15/2020 12:53 PM, Steven Katz wrote:
Why not use a VOM on a R x100 scale or something to connect directly across the 
meter  (with no resistors in the circuit) by cutting the shunt and bypassing 
the series resistor, to confirm the movement actually works?

-----Original Message-----
From: Amps <> On Behalf Of Artek Manuals
Sent: Friday, May 15, 2020 10:46 AM
Subject: Re: [Amps] SB220 Meter blown...follow up hope

With nothing else to loose IT removed the meter and found that ther are TWO resistors inside. 
One is in parallel with the meter movement and the other is in series. Those both have been 
"toasted"  a bit it seems like the parallel one is about 15k and the series one 
is about 1.8k. The 1.8k is open.

Can anyone verify these values they dont appear on the BOM since they are 
internal to the meter itself

Obviously replacing these two resistors is going to be a lot easier than 
finding a replacement meter movement



On 5/15/2020 1:14 PM, Artek Manuals wrote:
Comments below

On 5/15/2020 12:13 PM, Jim Thomson wrote:
Date: Fri, 15 May 2020 11:10:06 -0400
From: Artek Manuals <>
To: "" <>
Subject: [Amps] SB220 Meter blown

<I am resurrecting a SB220 that had an apparent classic Grid/plate
short <event. One of casualties appears to be the right hand meter movement.
<This is the one for Grid Current and HV. I am pretty far into it and
the <meter movement measures open , the internal shunt resistor is
blackened <( and open?)

<Anyone got a surplus movement from a parted out unit? Nothing found
on <evil-bay at the moment

<Dave NR1DX

## I believe harbach sells replacements. The heathkit shop might sell
They only have "meter diode/ resistor boards" no actual meter

The rest below are all good ideas but moot if I cant find a meter
movement, Nothing in my manual says what the actual values of the
movement is either 8^(

Next time be sure to install rvs connected 6A10s or 1N5408s between
B- of hv power supply caps..... and chassis. HV fuse, followed by 50
ohm glitch resistor is series with B+.

## Toss all the grid chokes and caps. Bond each of the 3 x grid pins
directly to chassis with strap.

## Install a 2nd HV series with one leg of the plate xfmr
secondary....either leg.

## Ok, now there is no way to blow anything up..including meters. Cro
bar anything u want,nothing happens except for a blown hv fuse.


Amps mailing list

Amps mailing list
<Prev in Thread] Current Thread [Next in Thread>