Little CRT

[S. Petrukhin]

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.

[Gyro]

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.

[CaptDon]

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?

[S. Petrukhin]

Oh yes, in the middle of the night I caught a child's mistake 6.3V AC RMS this is 6.3V DC. 

[S. Petrukhin]

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?

I 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.

[floobydust]

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).

[BrokenYugo]

http://lampes-et-tubes.info/cr/6LO1Ien.pdf

Looks to be an electrostatic scope tube.

[mikerj]

The Sinclair Microvision MTV1 used a small electrostatic deflection tube very similar to that.  If you look at the last post in this forum thread you'll find a link to the service manual which might be useful.

[Gyro]

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.

[Benta]

The 6LO1I that the OP is using has electrostatic deflection.

[Gyro]

So was the Sinclair.

[S. Petrukhin]

By the way, an interesting idea to make not only a TV, but also a monitor. 

[floobydust]

I was watching ancient UK sci-fi series Moonbase Alpha (Space 1999) from 1976 and I believe they use the Sinclair MTV-1B ?

Mini TV's schematics etc. worth looking at for the project Frank's Handgheld-TV pages
Sinclair MTV1 Service manual hard 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.

[Terry Bites]

[S. Petrukhin]

I was watching ancient UK sci-fi series Moonbase Alpha (Space 1999) from 1976 and I believe they use the Sinclair MTV-1B ?

Mini TV's schematics etc. worth looking at for the project Frank's Handgheld-TV pages
Sinclair MTV1 Service manual hard 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.

Fun idea to get a reamer saw directly on the deflecting plates