Re: [neonixie-l] Scope Clock SC200C
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/ >>> >>> >>> >>> >>> >>> ~ >>> *mcve...@gmail.com* >>> >>> >>> On Wed, Oct 20, 2021 at 4:16 AM GEK 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
Re: [neonixie-l] Scope Clock SC200C
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/ >> >> >> >> >> >> ~ >> *mcve...@gmail.com* >> >> >> On Wed, Oct 20, 2021 at 4:16 AM GEK 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
[neonixie-l] Re: Looking for some info about RCA DTF numitrons
I knew I'd seen the number, and found them just now: http://www.tube-tester.com/sites/nixie/dat_arch/Numitron_RCA_01.pdf at the bottom of the page, they are development numbers for the DR2200 series. /Martin On Tuesday, 26 October 2021 at 22:21:47 UTC+2 Dekatron42 wrote: > Tubes designated DTF are development numbers used by Apollo/RCA - it says > so at the bottom of their datasheets. > > /Martin > > On Tuesday, 26 October 2021 at 21:43:52 UTC+2 Bartek Ogryz wrote: > >> Hi! >> They appeared on eBay last days: DTF137, DTF138, DTF140 (or maybe DTF/37, >> DTF/38, DTF/40). What are theese? Anyone has some more knowledge about them? >> >> Bartek. >> >> BTW: If someone is interested in numitrons, quite rare Apollo DA-2500 are >> hiding on eBay: item no 254866404573. Unfortunatelly, as the seller told >> me, all that have left, are without markings... >> > -- 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/2c9ef490-64b9-49b0-b6d0-62b5b8e93682n%40googlegroups.com.
[neonixie-l] Re: Looking for some info about RCA DTF numitrons
Tubes designated DTF are development numbers used by Apollo/RCA - it says so at the bottom of their datasheets. /Martin On Tuesday, 26 October 2021 at 21:43:52 UTC+2 Bartek Ogryz wrote: > Hi! > They appeared on eBay last days: DTF137, DTF138, DTF140 (or maybe DTF/37, > DTF/38, DTF/40). What are theese? Anyone has some more knowledge about them? > > Bartek. > > BTW: If someone is interested in numitrons, quite rare Apollo DA-2500 are > hiding on eBay: item no 254866404573. Unfortunatelly, as the seller told > me, all that have left, are without markings... > -- 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/607c24e0-3073-46c2-ad68-0df29ffa099fn%40googlegroups.com.
[neonixie-l] Looking for some info about RCA DTF numitrons
Hi! They appeared on eBay last days: DTF137, DTF138, DTF140 (or maybe DTF/37, DTF/38, DTF/40). What are theese? Anyone has some more knowledge about them? Bartek. BTW: If someone is interested in numitrons, quite rare Apollo DA-2500 are hiding on eBay: item no 254866404573. Unfortunatelly, as the seller told me, all that have left, are without markings... -- 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/d01a9fca-7dac-4977-89b1-87984094dd21n%40googlegroups.com.
Re: [neonixie-l] Scope Clock SC200C
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/ > > > > > > ~ > *mcve...@gmail.com* > > > On Wed, Oct 20, 2021 at 4:16 AM GEK 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 >>
