[Heathkit] SB620 sweep cont'd

[W2HX]

Although its been a few years since I worked on mine, I do seem to recall two neons. One goes thru the front panel as a power indicator. The other I recall, was under the chassis away from view. I guess which was replaced would determine the result.

The original post did indicate the pilot light so maybe its not part of the problem 


On Tue, 12 Jan 2010 21:26:38 -0500, heathkit-bounces at mailman.qth.net wrote:
> You need to get the manual and read it. It explains the operation of this 
> relaxation oscillator!
> 
> Bob Macklin
> K5MYJ
> Seattle, Wa.
> "Real Radios Glow In The Dark"
> 
> ----- Original Message ----- 
> From: "Mike McCarty" <Mike.McCarty at sbcglobal.net>
> To: <heathkit at mailman.qth.net>
> Sent: Tuesday, January 12, 2010 6:12 PM
> Subject: Re: [Heathkit] SB620 sweep cont'd
> 
> 
> > john wrote:
> >> That's ri> >>
> >> http://www.oberlin.edu/physics/catalog/demonstrations/em/neonosc.html
> >>
> >> A clever use of a mundane part. :-)
> >
> > My first thought, when I heard "neon lamp", was the same. However,
> > looking at the schematic does not support that. It is being  used
> > solely as a regulator, I think. It is a voltage regulator stabilizing
> > the swept (not sweep) oscillator, but it is not an oscillator itself.
> >
> > The swept oscillator is V2B. The neon is fed from a low impedance
> > point in the power supply, and has no parallel capacitance to discharge.
> > There is a capacitor nearby, but it is used simply for decoupling
> > along with R12 to keep out high frequency noise.
> >
> > The lamp which  is  used as a relaxation oscillator is a different
> > lamp, not the one used for the power indicator. That lamp is near
> > V6A and is used as the sweep oscillator. It is, as one can note,
> > in parallel with a cap which it discharges. This is the sweep
> > oscillator. Different lamp, however. That lamp provides the
> > sweep control to the swept oscillator V2B.
> >
> > Mike
> > -- 
> > p="p=%c%s%c;main(){printf(p,34,p,34);}";main(){printf(p,34,p,34);}
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> >                                                               
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-- 
73 Eugene W2HX