I Built Another CRT TV from an AliExpress Kit-But It’s Still Not Working!
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- เผยแพร่เมื่อ 17 ก.ย. 2024
- Well, it's time I closed this chapter.......finally part 2 of my CRT DIY kit.
Want to try this kit your self? Search Ali Express for "5.5 Inch Black And White Tv Kit Electronic Production Parts Training Parts"
Part 1 Here: • I built CRT TV from a ...
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The problem with the compression at the bottom is caused by the vertical deflection circuit's being inadequate to scan the screen entirely from top to bottom. The vertical circuit produces a sawtooth wave at approximately a 60 Hz rate. if that sawtooth wave is not linear, you can get results like you're seeing.
There is a transistor or more than one transistor in that vertical circuit that is operating too close to its limits. If you look at a normal vertical waveform on an oscilloscope, you should see a smooth straight sawtooth. The waveform from this little TV is not smooth and straight; it is curved at the end, causing the compression seen in the picture.
The problem is most of these Learning kits are basically the result of using circuits designed by Tech-school students, combined with cheap dropout components from factories that produce Capacitors, resistors and all that, bundling that with a cheap plastic case and a PCB made in factories during times of low demand and then they sell it as learning kits. Often these kits need a lot of changes and and people often come up with their own improvements. I saw this a lot in forums about those cheap 6J9 tube buffer amps, that use a combination of low power tubes and transistors for the actual amplification of the audio and people changed the circuit with some re-routing to increase the sound quality. And yet i find these kids VERY fascinating because they are what they are and i love the fact that they make scrap parts at least available in these kits for some kind of useful purpose for folks like us who love to tinker around and solder it together for fun. Even if these circuits they use for the PCBs are far from being optimized or tested.
The funny thing is of course it worked for everyone but you. I barely knew how to solder and made multiple mistakes and broke several traces, yet i still got it to work.
Theoretically there could be a phase mismatch in the coils
but 120V at 60Hz shouldnt make any difference since its internally running on DC everywhere after the regulator circuit.
PAL/NTSC shouldnt make a difference since its black and white anyway and the b/w transmittions are pretty much compatible already
Both look like low B+, or the secondary voltages coming off the flyback are low.
Do you have a scope? Use an x10 probe to measure the voltage and flyback pulse at the collector of the HOT.
The schematic is terrible but variable resistor W4 in the power supply section should adjust the B+ regulation.
I mainly fixed flat panels, but I ripped the guts out of several CRTs.
If you've got a Raspberry Pi you can enable the composite video output and set it to PAL if you need a true reliable PAL video source.
Seen some colour motherboards for sale recommended off the original link posted in that video. Thanks for going over some of the caveats of these.
Not got any dead crts yet but hopefully we'll get some quality aftermarket solutions outside of 4K scalers soon.
I just watched part one the other day lol. Keep up the outstanding work. BZ
Awesome! Thank you!
Techknight might have some ideas about this thing. 📺
Those "cheap" Hyperkin consoles usually have a switch on them to change between NTSC and PAL. I think you can get the RetroN 1 (their NES clone) for about $20-25. Might be able to find a used one even cheaper. I wouldn't use them for gaming specifically, but for testing things out it could come in handy.
I was wondering about this project the other day. The board I bought is still unopened lol
I doubt the problem would be a power supply problem, or a signal compatibility problem. It could be on the high voltage circuit, or, more likely, the circuit that provides horizontal and vertical signals to the yoke.
The defect here is almost exactly like one I had on a security system CRT. Except that it would also distort the image a lot more. I couldn't figure out how to fix it.
Just today I received my 4 inch flat CRT from aliexpress and I’ve been having similar issues with screen size and that collapsed line, interesting that you uploaded this update just yesterday. This is at least giving me ideas for troubleshooting, even if you didn’t ultimately solve your issues.
What does tweaking pot W4 in the power supply section do for you?
@@coyote_den My pots are labelled RV (or possibly RU), and I don’t see anything near the 12V input.
It almost looks like the vertical linearity is off. I’m guessing there isn’t an adjustment for it. Maybe fiddle with the vertical driver see if there are components that may affect the linearity. The yoke coils may be wrong?
I find them quite expensive is there a place to buy this kit for cheaper
Unfortunately no I haven’t yet.
@@RetroTechorDie I will try to save some money then