Will do, Hopefully parts will be here by Friday. I may try and shotgun D35-38 and C52-53 before then as I should have spares around here.
Finger's crossed! - Gary On Wednesday, October 20, 2021 at 1:19:58 AM UTC-4 Tristan wrote: > Hi Gary, > > That's a bit odd. While I'm no EE I would have expected that removing U17 > would have blanked the display if the rest of the circuit was working > correctly. It looks Q13 should be conducting without U17 fitted and the > grid should become more negative with respect to the cathode to ensure > cutoff. I think you may need to look at the D35-38 and C52 & C53. > > - Tristan > > On Wednesday, October 20, 2021 at 12:42:53 PM UTC+10 GEK wrote: > >> Tristan - >> >> Thanks for those hints. the BLNK signal is pulsing at 60hz, and I >> swapped Q13 without any change. I also socketed U17 (6N137) while waiting >> for a replacement to arrive. Removing U17 from the circuit leaves the >> display unchanged, so it does appear that the blanking circuit is the >> culprit. >> >> I'll swap U17 once it arrives - and if that doesn't fix things start >> shotgunning the passives. >> >> Thanks again for the guidance, very appreciated! >> >> - Gary >> >> On Tuesday, October 19, 2021 at 10:04:24 PM UTC-4 Tristan wrote: >> >>> Also the voltage between the cathode and the blanking section should be >>> checked (I.e. the voltage across C51) and R65 and R67 should be checked (or >>> potentially replaced along with C51 if shotgunning it). The rest of the >>> high voltage supply appears to be working. >>> >>> - Tristan >>> On Wednesday, October 20, 2021 at 11:50:56 AM UTC+10 Tristan wrote: >>> >>>> I agree. The blanking is not working and as a result the beam is also >>>> faintly visible as it moves quickly between the characters as well drawing >>>> the arcs. It would be a good idea to check the BLNK signal on a scope and >>>> at least see that is is toggling but my money would be on the analogue >>>> blanking section. Given the other side of the optoisolator in the blanking >>>> section is at a fairly high negative voltage potential (as this reduces >>>> the >>>> need for the deflection amps to handle higher voltages) you will need to >>>> be >>>> careful when probing around there but I would start by checking the >>>> voltages across C54 and C55 (as long as you are confident doing so safely >>>> with the HV potential to ground). The correct voltages aren't specified on >>>> the schematic but they will be based on the grid cutoff voltage of the >>>> tube. If you wanted to avoid probing while the clock is on I'd be inclined >>>> to shotgun replace that section starting with the power supply diodes, >>>> caps >>>> and Q13 and then U17 and finally the passives and see how you go. >>>> >>>> - Tristan >>>> On Tuesday, October 19, 2021 at 4:24:11 PM UTC+10 iavine wrote: >>>> >>>>> From what I remember: >>>>> the characters are generated from circles, ellipses or lines which in >>>>> turn are created using sun or cosine waveforms >>>>> To make a character the beam is blanked for certain parts eg C is a >>>>> circle with a bit cut out. >>>>> >>>>> Looks like the blanking is not working as you’ve got a lot of circles >>>>> and ellipses there. >>>>> >>>>> Looks cool though >>>>> >>>>> Cheers >>>>> Ian V >>>>> >>>>> On 19 Oct 2021, at 06:08, Mac Doktor <themac...@gmail.com> wrote: >>>>> >>>>> >>>>> >>>>> >>>>> On Oct 18, 2021, at 7:53 PM, Gary Kaufman <geka...@gmail.com> wrote: >>>>> >>>>> I've now got a stable, but scrambled display (see pic's). I think I >>>>> have a problem with the shape generators but would appreciate any help or >>>>> suggestions you could offer. >>>>> >>>>> >>>>> Nah, that's just Cyrillic Neu Sans. >>>>> >>>>> >>>>> Terry Bowman, KA4HJH >>>>> "The Mac Doctor" >>>>> >>>>> "If only you could see what I've seen with your eyes."—Roy Batty, *Blade >>>>> Runner* >>>>> >>>>> -- >>>>> 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+...@googlegroups.com. >>>>> To view this discussion on the web, visit >>>>> https://groups.google.com/d/msgid/neonixie-l/3FBEDB26-E97C-44E2-B088-BDA7DAE4A020%40gmail.com >>>>> >>>>> <https://groups.google.com/d/msgid/neonixie-l/3FBEDB26-E97C-44E2-B088-BDA7DAE4A020%40gmail.com?utm_medium=email&utm_source=footer> >>>>> . >>>>> >>>>> -- 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 view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/00c69936-4f04-4a88-8343-f2f7d860135fn%40googlegroups.com.
