Re2: Vacuum tube VCO with expo control.

Harry Bissell harrybissell at
Tue Nov 23 08:07:26 CET 1999

"Aged" neon bulbs are available from Chicago Miniature Lamp (as a 'value added"
option). They burn them in for 16 hours and then select them for equal
brightness. This seems to indicate that (like tubes) most of the age decay
occurs real early in life. The NE-2H is the "radioactive" dark stabilized type.

DC operation will reduce life to 60% because of sputtering (loss of one cathode
emmisive material), but maybe the pulsed mode will compensate ???  Perhaps a
small resistor in series with the cap to lomit peak current might also help
(but messes up reset time...)

The OAC3 (??) voltage regulator cold cathode tube might also be made into an
oscillator ??? But is it available anymore...

:^) PS don't bother looking for Chicago Miniature web site... Its SLI something
and the data sheets aren't there...

Gilway Technical Lamp might be another choice...

HEY... How about a CCFL lamp as an oscillator... Even MORE voltage and it will
light up your front panel at the same time...  (only kidding)

:^) Harry

Rene Schmitz wrote:

> At 10:46 22.11.99 -0500, harrybissell at wrote:
> >What about neon aging as the cathodes decay... and limited life ??? does
> this mess up the expo conformity of just a pitch offset ???
> As the thresholds will only change the linear mA/Hz scale factor of the CCO
> (which ideally should go straight thru the origin) any ageing of the neon
> tube should only result in a pitch shift. Current doubling still means
> frequency doubling.
> Of course such long term effects aren't *very* annoying.
> But if this happens on a short time scale, it will be a pain. Hence
> temperature
> and light sensitivity will be probably the dominating short term effects
> for detune.
> I'm yet not really convinced by the practicability of such a VCO, but time
> will tell.
> The heat from the tube could disturb the expo convertor, messing up the
> scale. Therefore its best to place them apart. The tube however doesn't get
> very hot, I can touch it without pain. (Don't do that with the anode supply
> ;-)
> Bye
>  René
> opinionsexpressedher   | uzs159 at
> einarethatofmyemploy   |
> erandnotofmyself....   |

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