[Heathkit] SB620 sweep cont'd

[Bob Macklin]

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 right. A relaxation oscillator.
>>
>> 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);}
> Oppose globalization and One World Governments like the UN.
> This message made from 100% recycled bits.
> You have found the bank of Larn.
> I speak only for myself, and I am unanimous in that!
> ______________________________________________________________
> Heathkit mailing list
> Home: http://mailman.qth.net/mailman/listinfo/heathkit
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Heathkit at mailman.qth.net
>
> List Administrator: Duane Fischer, W8DBF
> ** For Assistance: dfischer at usol.com **
>
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>