That may just be one of the worst PCB layouts I've ever seen. On Wednesday, October 20, 2021 at 8:33:41 AM UTC-5 martin martin wrote:
> Here's a simple one > > https://www.tindie.com/products/howchon/osc45-oscilloscope-clock-kit-for-many-crt-types/ > > > > > > ~ > *mcve...@gmail.com* > > > On Wed, Oct 20, 2021 at 4:16 AM GEK <geka...@gmail.com> wrote: > >> 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+...@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 >> >> <https://groups.google.com/d/msgid/neonixie-l/00c69936-4f04-4a88-8343-f2f7d860135fn%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. 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