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Project with CRTs. Anyone interested?

 
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[Frankie]



Joined: 16 Jun 2014
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Location: Italia


PostLink    Posted: Wed Aug 28, 2019 6:43 am    Post subject: Project with CRTs. Anyone interested? Reply with quote


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Hi! I've made this github page about a project i'm doing. This involves High End CRTs of 2001/02/03 and so on with 100 Hz Scanning. I post the link: https://github.com/telemoses/crt-pi

Briefly the project consists in making a new brain for a CRT TV 100Hz. The brain is a Raspberry Pi which controls an High End Output Processor (aka TDA9332H). This HOP is able to handle basically lots of multysinc resolutions from 240p to 720p including interlaced one obviously. It can be used so for HD up to 1080i and for retrogaming down to 240p. Moreover it can be an ecological way to reuse old CRT TV instead of trhowring them away. Guess it's kinda impossible recommercializing CRT display to a medium user.. but for who knows that CRTs has some excellent pros, it can be a really cool project!

Anyway.. I wanted to ask most of all if it make sense. If someone wants to help me in some way is free to chat with me here or on Github.

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kal
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PostLink    Posted: Thu Aug 29, 2019 12:36 pm    Post subject: Reply with quote

Maybe I'm not understanding, but it sounds like you're designing a scaler?

Kal

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[Frankie]



Joined: 16 Jun 2014
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Location: Italia


PostLink    Posted: Thu Aug 29, 2019 1:29 pm    Post subject: Reply with quote

kal wrote:
Maybe I'm not understanding, but it sounds like you're designing a scaler?

Kal


No, it's more like a new brain for the TV or a new signal board

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kal
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PostLink    Posted: Thu Aug 29, 2019 4:26 pm    Post subject: Reply with quote

But that's what a scaler is, something that allows you to choose any output resolution you like (progressive or interlaced) at any refresh rate. Basically what you wrote here:

[Frankie] wrote:
This HOP is able to handle basically lots of multysinc resolutions from 240p to 720p including interlaced one obviously. It can be used so for HD up to 1080i and for retrogaming down to 240p.


What does your solution do that (say) something like a Radiance can't? (The Radiance does a million other things too of course - completely flexible scaling/refresh rate changes is only a small part of what they do).

Kal

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[Frankie]



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Location: Italia


PostLink    Posted: Thu Aug 29, 2019 6:17 pm    Post subject: Reply with quote

kal wrote:
But that's what a scaler is, something that allows you to choose any output resolution you like (progressive or interlaced) at any refresh rate. Basically what you wrote here:

[Frankie] wrote:
This HOP is able to handle basically lots of multysinc resolutions from 240p to 720p including interlaced one obviously. It can be used so for HD up to 1080i and for retrogaming down to 240p.


What does your solution do that (say) something like a Radiance can't? (The Radiance does a million other things too of course - completely flexible scaling/refresh rate changes is only a small part of what they do).

Kal


It's not a Radiance, is a part of the TV. The TV is SD 100Hz, with this you hopefully go a little bit higher. With this u substitute the inner Small Signal Board of the TV with a new one that u can modify resolutions, and all the image parameter trough i2c. Natively this TVs has got only one resolution (PAL 100Hz). With this internal board u can go theorically from 240p to 1080i.

Have you read the Github page? There there is a more detailed description Wink

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kal
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PostLink    Posted: Thu Aug 29, 2019 7:03 pm    Post subject: Reply with quote

I see.

While every CRT TV has similar principles as to how the deflection circuitry works to paint the image, how that's done is different in every model so your circuit before that that interfaces to the deflection circuitry would have to be interfaced and used different for every TV I would imagine, no? So every TV would require a custom designed solution right?

TVs are rarely ever over-engineered to allow for higher scanrates or refresh rates than what they were designed for as the companies know that doing so is a waste of money on their part. For example, if you have a SD TV that only accepts PAL today (576i), the deflection circuitry will not be designed to scan much higher than that. If you want to do 1080i you need to more than change the circuitry that creates the image and timing signals. You need to also change all of the high voltage circuitry to accepts multiple scanrates and refresh rates. In most cases fixed resolution TVs don't have HV circuitry to handle anything but the one resolution that they expect to recieve. The TV manufacturer wouldn't put the cost of this in the TV and then never allow the user to use it. So you need to have higher speed / higher power transformers, MOSFETs, and so forth. Not just the control circuitry. You'd be replacing basically everything but the picture tube probably?

That said, have at it and let us know how it goes! Experimentation is good and I wouldn’t want to dissuade anyone from trying something they’re interested in. Good luck!

Kal

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kal
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PostLink    Posted: Thu Aug 29, 2019 11:00 pm    Post subject: Reply with quote

Seems much of what I’ve said here was already covered in this previous thread: http://www.curtpalme.com/forum/viewtopic.php?t=40265

Kal

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[Frankie]



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PostLink    Posted: Fri Aug 30, 2019 6:09 am    Post subject: Reply with quote

For what i know, a 100Hz TV handle a maximum of almost 40 KHz of Horizontal Deflection so PSU and all deflection circuits theorically should handle a 1080i signal for instance. It's not an higher scan-rate. It's basically the same for what i see. Anyway.. i checked the service manual of another CRT TV that accepts 480p/480i/576i/576p/720p/1080i which is the 32PW9551/12 from Philips. This set has got basically the same deflection circuitery with the same MOSFET (BU2520DX) and the same HOP (TDA9330H which is a previous version of the TDA9332H) of my 100Hz CRT. Anyway when i'll try doing this i'll let you know if it works anyway Wink
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PostLink    Posted: Sun Sep 01, 2019 1:43 am    Post subject: Reply with quote

Don't let out the magic smoke!
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