Ok, so I'm stumped (again)... I have replaced D35-38, C52, C53, C54, C55, Q1, C51 and U17. R67, F68, R69, R70 and R71 measure correctly in circuit. I've confirmed pulsing on the BLNK- signal at 60hz I've also swapped U5 (74HC74) and U4 (74HC151). I've swapped the CRT.
Curiously I need to have the Bright potentiometer (R11) at maximum to get an image. Could something in the High Voltage Supply be causing problems with the blanking? On Thursday, October 21, 2021 at 3:05:10 PM UTC-4 Paul Andrews wrote: > Hah yes. I have one of its brethren that is even more 'eclectic'. > > On Wednesday, October 20, 2021 at 8:04:03 PM UTC-4 Terry S wrote: > >> >> 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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