Little CRT - Page 1
Forum section: electronics / beginners

author: S. Petrukhin
author_rank: Super Contributor
timestamp: January 18, 2021, 10:02:56 pm
content: Friends, hello!A little bit of design work squeezed me and I want to distract myself, relax - do something completely different from the heart. I have a small CRT Soviet 6LO1i and I want to make a TV out of it.But I do not understand anything about lamp technology I have a funny question for a pro:1. Is it possible to supply the filament with a DC voltage relative to Gnd?2. What should be the polarity?3. If the filament voltage is 6.3V AC, then it is RMS and the DC should be 4.45V?Reliability and durability doesn't matter, it's just a souvenir for a very rare use.

author: Gyro
author_rank: Super Contributor
timestamp: January 18, 2021, 10:18:47 pm
content: Looks like a fun project.Yes, assuming that the tube is indirectly heated, then DC heating is fine. There is no preferred polarity. The DC heater voltage should be.... 6.3V.The only thing you need to ensure is that the filament potential isn't too far from that of the Cathode (probably within 100V). Don't go sticking -1kV on the cathode with a ground referenced filament.

author: CaptDon
author_rank: Super Contributor
timestamp: January 18, 2021, 10:21:16 pm
content: The RMS value of A.C. is an approximate equivalent of the D.C. heating value, therefore 6.3vac or 6.3vdc is acceptable. How do you plan to make a t.v. out of it? You must have all of the correct voltages as well as the correct signals for vertical and horizontal deflection as well as grid drive for the video signal. Where are you planning on getting these?

author: S. Petrukhin
author_rank: Super Contributor
timestamp: January 18, 2021, 10:39:09 pm
content: Oh yes, in the middle of the night I caught a child's mistake 6.3V AC RMS this is 6.3V DC.

author: S. Petrukhin
author_rank: Super Contributor
timestamp: January 18, 2021, 10:50:12 pm
content: Quote from: CaptDon on January 18, 2021, 10:21:16 pmI plan to make a pulse converter at 1200V and divide the resistors into an accelerating grid, a focusing grid, a modulating grid and a cathode so that the catode is slightly higher than Gnd. On the plates to the left and up, apply a constant beam displacement voltage to the upper left point, and the second sides of the plates supply a unipolar sweep signal. I want to get a video signal from an unnecessary DVB-T we have only a digital TV signal on the air in Russia. It has an HDMI output, there is a complex-video, it is a pity, there is no VGA with a separate scan synchronization signal. I will think about how to gnaw out the HDMI signals. The scan will probably be done digitally on the STM32F103C8.

author: floobydust
author_rank: Super Contributor
timestamp: January 19, 2021, 02:14:06 am
content: First, consider if the CRT is built for electrostatic (analog oscilloscope) or electromagnetic (TV) deflection.If you see CRT pins for X, Y plates then it's electrostatic deflection and it is customary to keep the plates at voltages that transistors can drive, i.e. around 150VDC.This means the CRT cathode (and filament) must have a large -ve potential, like -2,000V as well as the anode voltage(s).

author: BrokenYugo
author_rank: Super Contributor
timestamp: January 19, 2021, 02:47:49 am
content: http://lampes-et-tubes.info/cr/6LO1Ien.pdfLooks to be an electrostatic scope tube.

author: mikerj
author_rank: Super Contributor
timestamp: January 19, 2021, 01:09:37 pm
content: The Sinclair Microvision MTV1 used a small electrostatic deflection tube very similar to that. If you look at the last post inthis forum threadyou'll find a link to the service manual which might be useful.

author: Gyro
author_rank: Super Contributor
timestamp: January 19, 2021, 01:31:20 pm
content: Interesting @mikerj, I love some of the back of a fag packet schematics!@S. Petrukhin: Note that the Sinclair CRT is/was directly heated, or at least had the indirectly heated cathode attached to one of the heater pins. That's pretty unusual (maybe a narrow neck pin number limitation). It is worth checking that your CRT doesn't have the same. If there is a separate cathode pin on your CRT, then as I said, heater polarity isn't relevant.

author: Benta
author_rank: Super Contributor
timestamp: January 19, 2021, 06:26:17 pm
content: The 6LO1I that the OP is using has electrostatic deflection.

author: Gyro
author_rank: Super Contributor
timestamp: January 19, 2021, 08:03:30 pm
content: So was the Sinclair.

author: S. Petrukhin
author_rank: Super Contributor
timestamp: January 19, 2021, 08:56:26 pm
content: By the way, an interesting idea to make not only a TV, but also a monitor.

author: floobydust
author_rank: Super Contributor
timestamp: January 19, 2021, 10:08:44 pm
content: I was watching ancient UK sci-fi seriesMoonbase Alpha (Space 1999)from 1976 and I believe they use theSinclair MTV-1B?Mini TV's schematics etc. worth looking at for the projectFrank's Handgheld-TV pagesSinclair MTV1 Service manualhard to read the way he biased the 2" CRT.I imagine the cathode/filament and control grid are at say at -750V or so, the deflection plates can then be around 150-300V to be transistor driven.

author: S. Petrukhin
author_rank: Super Contributor
timestamp: January 22, 2021, 08:09:06 pm
content: Quote from: floobydust on January 19, 2021, 10:08:44 pmFun idea to get a reamer saw directly on the deflecting plates