[Heathkit] SB620 sweep cont'd

[john]

That's right. A relaxation oscillator.

http://www.oberlin.edu/physics/catalog/demonstrations/em/neonosc.html

A clever use of a mundane part. :-)
John K5MO


At 07:33 PM 1/12/2010, W2HX wrote:
>You cannot replace the neon. It is, in fact, essential to the sweep. As the
>voltage across it increases, so does the horizontal deflection of the beam.
>Once the neon reaches its breakdown voltage, the sweep goes back to zero to
>start again.
>
>This is my understanding of the circuit, I am sure others can elaborate (and
>refute!)
>
>73 Eugene W2HX
>
>-----Original Message-----
>From: heathkit-bounces at mailman.qth.net
>[mailto:heathkit-bounces at mailman.qth.net] On Behalf Of Michael Tortorella
>Sent: Tuesday, January 12, 2010 6:15 PM
>To: heathkit at mailman.qth.net
>Subject: [Heathkit] SB620 sweep cont'd
>
>G'day all,
>
>Thanks to all who replied with suggestions on the above.  I did some voltage
>checks on V3, the sweep tube, and all are about 20% low.  Hmmm.  I had
>replaced the neon pilot light with an incandescent, driving it off the B+
>line with a 27k resistor in series.  Is the neon bulb essential to the sweep
>circuit?  It doesn't look like it is, but maybe the current drawn by the
>pilot light is pulling the B+ down?
>
>Thanks in advance and 73
>
>Mike W2IY
>
>______________________________________________________________
>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
>
>
>______________________________________________________________
>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