I agree, that bright dot must be the beam resting on the same spot for too long. I'll check the code, where the refresh seems to be driven by the blanking pin, so with no blanking currently connected (still missing a part), the dot is not been managed.
I thought that the same settings as for 3RP1A would work on 3LO1i but I guess not, they must have different physical characteristics. Il giorno martedì 28 novembre 2023 alle 17:05:12 UTC Grahame ha scritto: > I would guess that the bright spot is where the beam rests after drawing > the face and is waiting for the next refresh trigger. > > My own scope clock draws each face once every 20mS (16.66mS in 60Hz land) > synchronised to the mains. If a particular face takes, say, 8mS to draw > then the beam is parked somewhere and left blanked for the remaining 12mS > (in this example) waiting for the next face refresh trigger. So if the beam > is left on for the waiting period then it will appear as a very bright spot > at the parked position. You'd have to investigate the software you're using > for what triggers the face drawing and what happens in the waiting period. > > Grahame > On 27/11/2023 22:50, Max DN wrote: > > I'm attaching the voltage divider that I am using and the one that I'm > going to try using values calculated assuming 0.5mA current draw (which I > understand makes sense for this CRT). > > Sharing this useful website to calculate resistor values using parameters > from the datasheet, it is starting to make sense now! > > https://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/qst/1946/12/page45/index.html > > Blanking pin currently disconnected (still waiting for an optocoupler). I > wonder whether that will fix the bright spot (of course it will fix the > smears on the display). > > @ gregebert - I may find this latest update useful > > Il giorno lunedì 27 novembre 2023 alle 09:28:02 UTC Max Di Noi ha scritto: > >> Ok, I managed to make some improvements by changing some resistors on the >> voltage divider, I'll post my new layout later. >> >> Much better now, although I need to better understand how to calculate >> resistor values as at the moment I don't know current draws by each crt >> pin. >> >> I get a very bright spot on the clock image, I don't know if that's >> because I have not connected the blanking circuitry yet or overvoltage on >> A1 (I'm waiting for an optocoupler, hopefully it arrives this week). >> >> Picture attached. Getting there. >> >> >> -------- Original message -------- >> From: 'Grahame' via neonixie-l <neoni...@googlegroups.com> >> Date: 26/11/2023 11:21 (GMT+00:00) >> To: neoni...@googlegroups.com >> Subject: Re: [neonixie-l] Scope Clock with 3LO1i >> >> Hi >> >> £55 is expensive - you should be able to get them for £30. >> >> Have you tied the deflection plates to A2 for testing purposes or left >> them floating? They should be tied to A2. >> >> Can you turn the brightness pot down to fully extinguish the dot? If not >> you need to be able to. >> >> Grahame >> On 25/11/2023 18:28, Max DN wrote: >> >> @Grahame >> Thanks for the suggestion. I didn't know about CV2302 DH3-91, I see >> Langrex is selling it for £55 on eBay. >> >> Yes, my voltages were off. I have made some changes: >> Cathode is now -350V to ground >> A1 is +30V above cathode >> A2 is +150V above ground, that is +500V above cathode >> I'm having some problems with Grid voltage, I'm guessing... >> >> >> @gregebert >> This is the pinout I'm using: >> Pins 1-14 heater >> Pin 2 Cathode >> Pin 3 Grid G1 >> Pin 4 A1 (focus anode) >> Pin 5 n/c >> Pin 6 Grid G2 >> Pin 7 X1 >> Pin 8 X2 >> Pin 9 A2 (acceleration anode) >> Pin 10 Y1 >> Pin 11 Y2 >> Pin 12 Grid G3 >> Pin 13 n/c >> Pins 3-6-12 are all internally connected, other than on mine 3 is no >> longer soldered on the grid. >> >> Pin 3 or 6 or 12 (Grid) is connected to -525V (that's 40V above -485V >> negative voltage doubler in Cathode Corner's schematic), still not good >> (pic attached). I connected a few resistors in series 500k, then 1M to >> bring voltage down up to -250V, with not much difference. So it's clear I >> don't understand how to connect the Grid pin!! >> >> I did find a schematic here (suggests to reduce max negative voltage rail >> to -300V): >> https://www.catahoulatech.com/index.php?product=KIT-0001 >> >> https://www.catahoulatech.com/products/KIT-0001/OscilloscopeCrtDriverData.pdf >> >> I also find something else that is exactly what I'm trying to do. It's >> using different POTs and +350V vs -350V (whereas I'm using +250V and >> -485V)... Schematic attached. >> >> >> Il giorno sabato 25 novembre 2023 alle 10:07:25 UTC Grahame ha scritto: >> >>> Hi Max >>> >>> https://threeneurons.files.wordpress.com/2015/05/3lo1i.pdf >>> >>> gives the normal operation acceleration anode A2 voltage as 500V (WRT >>> cathode) and the focus anode A1 as 0 to 50V. Your voltages are higher, >>> especially the focus anode voltage. Hence the green splat rather than a dot. >>> >>> My experience with this tube and the 6LO1i which is the slightly larger >>> rectangular version is very poor. The phosphor literally turned grey, then >>> black and the light emission faded over a couple of months in use. It >>> wasn't that the phosphor burned with the image but the phosphor greyed >>> uniformly. Most odd. Might have it been a bad batch of tubes? IIRC someone >>> else has seen this effect. >>> >>> If you want a small tube then look out for a 1CP1 or DH3-91 or CV2302 >>> would be my suggestion. >>> >>> Grahame >>> On 24/11/2023 22:49, Max DN wrote: >>> >>> Hello, >>> >>> I managed to successfully build a scope clock almost entirely based on >>> Cathode Corner design using CRT 3RP1A. >>> >>> I happen to have a 3LO1i (I know it only lasts for 1000 hours...) and I >>> tried to modify the voltage doublers to use my circuit with this CRT but >>> I'm not too sure about the correct voltages. At the moment I have: >>> Grid: -480V; HTR2: -380V; HTR1: -384V; HTR1-HRT2: 6.3VDC; CATH: -384V; >>> A1: -248V; A2: +200V >>> >>> However I cannot get a small green dot, only a wide green shade, picture >>> attached. >>> I'm sure I'm doing something wrong with the voltage divider. Any >>> suggestions please? >>> >>> Thank you, >>> Max >>> >>> -- >>> 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/669f964f-9fec-4cb1-8a03-f06a1749131en%40googlegroups.com >>> >>> <https://groups.google.com/d/msgid/neonixie-l/669f964f-9fec-4cb1-8a03-f06a1749131en%40googlegroups.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/3e5e58ba-b3f9-41ae-95c0-2fd4ac9291c4n%40googlegroups.com >> >> <https://groups.google.com/d/msgid/neonixie-l/3e5e58ba-b3f9-41ae-95c0-2fd4ac9291c4n%40googlegroups.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/05e95c29-8bc5-4b6f-abc2-c211936daedd%40googlemail.com >> >> <https://groups.google.com/d/msgid/neonixie-l/05e95c29-8bc5-4b6f-abc2-c211936daedd%40googlemail.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/95489733-8556-4c02-8828-033acd00df03n%40googlegroups.com > > <https://groups.google.com/d/msgid/neonixie-l/95489733-8556-4c02-8828-033acd00df03n%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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