I'm getting approximately: Astig +124v Focus/A2 -852v Cathode/Bright -1210v Grid -1262v
The manual suggests that the Brightness has about -1300v, focus about -900v and Astig +300v I can adjust the Astig from 0 - 240 but the image is sharpest at 124v. - Gary On Wednesday, October 27, 2021 at 10:48:16 AM UTC-4 GEK wrote: > I probably do have a 10meg resistor down in my cellar, time to dig. I > wasn't sure if I'd need to create an actual voltage divider with 2 > resistors/ground wire so that's helpful. I'd hate to destroy a Fluke... > > On Wednesday, October 27, 2021 at 1:06:19 AM UTC-4 gregebert wrote: > >> Most DMMs have 10Meg input impedance, so you can put a 10meg resistor >> in-series with your meter, and measure double the voltage. It wont be >> exact, but pretty close. If you really need an exact measurement, then >> measure a stable lower voltage without the resistor, then again with it. >> Dividing those 2 measurements will give you a ratio close to 2.0, and you >> can use that when measuring your high voltage. >> >> >> On Tuesday, October 26, 2021 at 8:40:54 PM UTC-7 GEK wrote: >> >>> Thanks everyone for the hints, I'll look more closely at the HV - I'm a >>> bit shy about measuring as I don't have a meter that will go to -1300v for >>> the bright. >>> >>> - Gary >>> >>> On Tuesday, October 26, 2021 at 3:17:49 PM UTC-4 Bartek Ogryz wrote: >>> >>>> I'm not familiar with that project and that circuit, but based on my >>>> experience in CRT TV repairs, if you have a proper blanking signal, >>>> something must be wrong with HV as Tristan said. >>>> Grid1 - negative voltage on this grid allows electrons to flow >>>> (brighter picture), 0V blocks them (darkness). This grid can be driven by >>>> the blanking signal, >>>> Grid2 - is the screen grid, high voltage accelerates the electrons and >>>> brightens the screen. If that voltage is too high, it can "force" >>>> electrons >>>> to flow, regardless of the Grid1 voltage. >>>> Chceck the main power supply first - if it's voltage is too high, all >>>> HV voltages will also be too high. >>>> wtorek, 26 października 2021 o 05:02:21 UTC+2 Tristan napisał(a): >>>> >>>>> The brightness pot needing to be turned right up still suggests that >>>>> you have a problem with grid voltage control. I'd expect to see some >>>>> higher >>>>> frequencies much higher than 60Hz on the BLNK- signal as well though. I'd >>>>> be surprised if the problem was in the supply sections for the cathode or >>>>> anode given that it is mostly working in your photo but there could be an >>>>> issue with the specific section of the supply dedicated to the grid and >>>>> it >>>>> is referenced to the cathode. Although you have now replaced most of the >>>>> potentially offending components unless you have an open winding on the >>>>> transformer. You could check the resistance across pins 4,5 and 6 of the >>>>> transformer. I'd expect them all to read fairly low. >>>>> On Tuesday, October 26, 2021 at 10:20:26 AM UTC+10 GEK wrote: >>>>> >>>>>> 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/ >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> ~ >>>>>>>>> *[email protected]* >>>>>>>>> >>>>>>>>> >>>>>>>>> On Wed, Oct 20, 2021 at 4:16 AM GEK <[email protected]> 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 <[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/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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