If the transformer lacks a real center-tap then a virtual center-tap can be used instead. Simply use a pair of resistors of a reasonable value, say 470ohm as a divider across the secondary of the transformer and use the center of the divider instead to bias the cathodes instead. If you were running an even number of tubes in series you could use the middle filament connection instead.
On Sunday, November 15, 2015 at 7:17:16 AM UTC+10, Chaos Hydra wrote: > > yeah, that's what I need to do next, reduce the background illumination of > those tubes. I will look into this. Thanks. > > On Saturday, November 14, 2015 at 4:33:27 AM UTC-5, Dekatron42 wrote: >> >> I am glad it works better now! >> >> Have a look at paragraph 6.2 in the Noritake link, there they use a zener >> diode to bias the center tap, you can usually just use a string of ordinary >> diodes to try out what bias voltage that you need for your design to have a >> proper cut-off voltage. >> >> Then when you know that cut-off voltage you can either use one zener with >> the nearest voltage or you can use two (or a string of diodes) and then you >> can short part of this diode chain to have an effective dimming capability >> - the Russians (probably others too) used this way of dimming the VFD >> displays in clocks for night usage. >> >> So using a center-tapped transformer has its good sides. >> >> /Martin >> >> On Saturday, 14 November 2015 03:30:41 UTC+1, Chaos Hydra wrote: >>> >>> I made a clean cut on the trace and patched in a 10VAC transformer. That >>> solved the overheating filament problem and now has a decent brightness >>> overall. The only problem is: the certer tubes' "off segments" are quite >>> bright. It is kind of difficult to read sometimes. >>> >>> On Friday, November 13, 2015 at 2:52:28 AM UTC-5, gregebert wrote: >>>> >>>> It's worth trying 1 cut between the 12VDC supply and the filament >>>> chain, and applying AC between GND and the cut-trace. It may not give you >>>> the best results, but it could produce less variation in brightness. >>>> >>>> >>>> -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/5521c211-e766-4c0f-85a5-82353b78b3f5%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
