I built CRT TV from a kit on Ali Express

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I built CRT TV from a kit on Ali Express

Postby Harry Dalek » Wed Jun 08, 2022 10:22 pm

I found this video interesting Television Kits have been few and far between over the the decades this must be the last CRT version
https://hackaday.com/2022/02/09/build-your-own-crt-tv/

youtu.be/cRr6OTpLGD8
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: I built CRT TV from a kit on Ali Express

Postby Steve Anderson » Wed Nov 30, 2022 7:33 pm

If it's still available I'd be interested in buying one. But given the schematic I would simply replace all the supplied resistors and capacitors with decent quality parts I can get locally at a fairly small cost. I'd also omit the RF tuner making it a baseband video input only. OK, the case and mechanical parts are crappy, but given there are few 5" or so B/W monitors around these days it's all there might be.

What isn't mentioned is is it 525/60 or 625/50, or selectable? As the guy in the video is in the US I assume 525. However it comes with a 220V transformer so there may be hope yet for most of us 625 guys. A 5" or so screen is ideal for a 120/128 monochrome SSTV, and particularly NBTV display after up-conversion. However, China does use 525 on 220V, or more correctly - did.

As there is no vertical output transformer this thing may be OK at 50Hz as opposed to 60Hz. The difference between 525 and 625 horizontal rate should be of no consequence.

I've tried finding the seller on Alibaba but no go. If anyone has a link I would be thankful...

Steve A.
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Re: I built CRT TV from a kit on Ali Express

Postby Harry Dalek » Fri Dec 02, 2022 1:51 pm

Steve Anderson wrote:If it's still available I'd be interested in buying one. But given the schematic I would simply replace all the supplied resistors and capacitors with decent quality parts I can get locally at a fairly small cost. I'd also omit the RF tuner making it a baseband video input only. OK, the case and mechanical parts are crappy, but given there are few 5" or so B/W monitors around these days it's all there might be.

What isn't mentioned is is it 525/60 or 625/50, or selectable? As the guy in the video is in the US I assume 525. However it comes with a 220V transformer so there may be hope yet for most of us 625 guys. A 5" or so screen is ideal for a 120/128 monochrome SSTV, and particularly NBTV display after up-conversion. However, China does use 525 on 220V, or more correctly - did.

As there is no vertical output transformer this thing may be OK at 50Hz as opposed to 60Hz. The difference between 525 and 625 horizontal rate should be of no consequence.

I've tried finding the seller on Alibaba but no go. If anyone has a link I would be thankful...

Steve A.


I think it still is
https://www.aliexpress.com/item/1782606 ... 208bc4e24c

I think he had trouble with the power supply as if teh supplied Transformer was to low amp wise to drive the deflection electronics from memory .
pretty much pay that for just the crt if you are lucky to find one these days .
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: I built CRT TV from a kit on Ali Express

Postby Steve Anderson » Fri Dec 02, 2022 2:17 pm

Thanks for the link Harry, I'll follow up on it...

I noted his concerns about the transformer, I'd do the same as him, replace it with something better, and/or provide a DC input - from an old laptop power supply/charger modified for whatever voltage this needs....later, it appears to be 12V, - current, I'd guess 1-1.5A, but maybe less.

Looking at the circuit diagram you can see a DC input jack, though I'm not too keen on how it's been implemented, but that's an easy fix.

Click the image to zoom in, it's about 2700x1800, monochrome GIF.

Another thing I noticed - there's no mention or indication of a focus control whether electromagnetic or electrostatic. OK, it's a small screen, but some form of focus adjustment would be an improvement once the deflection and power supply problems are overcome. Getting a datasheet for the CRT is probably nigh on impossible.

The buzzing/hum on the audio mentioned in the video is probably down to pin 7 of IC2 being open-circuit. It's an internal bypass point and requires a capacitor from pin 7 of around 10-22uF/16-25V to ground/0V (IC2 pin 4). This reduces the ripple/hum from the supply to the speaker by around 40db (by 100). IC2 is a 'copy' LM386, see original datasheet. What the Chinese do to save a cent (literally).

Steve A.

LM386.pdf
(264.42 KiB) Downloaded 82 times


TV diagram.gif
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