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

[Steven Katz]

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 <amps-bounces at contesting.com> On Behalf Of Artek Manuals
Sent: Friday, May 15, 2020 10:46 AM
To: amps at contesting.com
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

Hellllpppppp!!!

Dave
NR1DX

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 <Manuals at ArtekManuals.com>
>> To: "amps at Contesting.com" <amps at contesting.com>
>> 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 
>> em.
>
> They only have "meter diode/ resistor boards" no actual meter 
> movements
>
> 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 fuse...in 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.
>>
>> Jim VE7RF
>>
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>

--
Dave
Manuals at ArtekManuals.com
www.ArtekManuals.com


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