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

[Gary Schafer]

If the movement is open on yours you can use a movement from a heath kit
wattmeter. They are the same size meter but the movement has a different
sensitivity. You will need to adjust the shunt/series resistors accordingly
in the amp to make it work. there some articles on the net about doing this.
Somewhere I have the articles if you get stuck, let me know and I will see
if I can find them.

73
Gary  K4FMX 

> -----Original Message-----
> From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of 
> Artek Manuals
> Sent: Friday, May 15, 2020 12:46 PM
> 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
> >>
> >> _______________________________________________
> >> Amps mailing list
> >> Amps at contesting.com
> >> http://lists.contesting.com/mailman/listinfo/amps
> >
> 
> --
> Dave
> Manuals at ArtekManuals.com
> www.ArtekManuals.com
> 
> 
> -- 
> This email has been checked for viruses by Avast antivirus software.
> https://www.avast.com/antivirus
> 
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps