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 <[email protected]> wrote: >>> >>> >>> >>> >>> On Oct 18, 2021, at 7:53 PM, Gary Kaufman <[email protected]> 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 [email protected]. >>> 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 [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/7ddec566-921b-483a-9b35-2b098d88f812n%40googlegroups.com.
