sorry got it upside down must have been lost in the translation :-) so you need some 'good old' NE's. If you can find some in the UK/EU I can send you a few.
-pete On Thu, Nov 16, 2017 at 1:08 PM, David C. Partridge < [email protected]> wrote: > Errm - I'm looking for around 65-75V range so I end up near but not > exactly the same as the 70V ones that are already there. > > -----Original Message----- > From: volt-nuts [mailto:[email protected]] On Behalf Of Pete > Lancashire > Sent: 16 November 2017 18:24 > To: Discussion of precise voltage measurement > Cc: [email protected] > Subject: Re: [volt-nuts] Neon bulbs for HP 3420B or 419A chopper circuit > > I've seen 95V but nothing as high as 125V. > > The high brightness ones are usually 95V > > http://www.farnell.com/datasheets/57560.pdf > > > -pete > > > On Thu, Nov 16, 2017 at 6:38 AM, David C. Partridge < > [email protected]> wrote: > > > In an earlier post I quoted the following description of the > > photo-chopper circuit from the 419A manual > > > > 4-43. Assume that DS1 lights when the input is applied to T2. > Capacitor > > C1 charges until the oscillator switches the input, and DS1 goes off. > > When > > the oscillator switches again, the charge on C1 insures that DS2 fires, > and > > DS1 stays off. This cycle continues with DS1 and DS2 firing as long as > > there is output from the oscillator. CR1 and CR2 prevent the > > capacitor from discharging through R1 and R2 > > > > That description also applies to the 3420B chopper. > > > > For this to work as described, George Einst says that the striking > > characteristics on the neons are critical, which I totally believe > > given what's happening in mine. > > > > AFAICT, *both* neons are striking on every +ve portion of the square > > wave drive signal, so the flip-flop behaviour doesn't happen. > > > > I checked on the curve tracer, and both neons strike at almost exactly > 70V. > > Both are also totally clear which suggests to me that they are not the > > originals. > > > > Does anyone have any idea how much the strike voltages would need to > > differ for this to work, and does anyone have any suitable neons - the > > only ones I have are these shorter ones and they strike at about 125V. > > > > These are the longer bodied neons (glass about 5/8" long). > > > > Thank you > > Dave Partridge > > > > > > _______________________________________________ > > volt-nuts mailing list -- [email protected] To unsubscribe, go to > > https://www.febo.com/cgi-bin/ mailman/listinfo/volt-nuts and follow > > the instructions there. > > > _______________________________________________ > volt-nuts mailing list -- [email protected] To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > > _______________________________________________ > volt-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/volt-nuts > and follow the instructions there. > _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
