CRT RGB Modification/Hack [56K Warning]

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sickle
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Re: CRT RGB Modification/Hack [56K Warning]

Post by sickle » May 3rd, 2015, 11:55 am

Hahaha, I when making that post that I didn't actually know the name of the coils that aim the beam. But yeah those guys.
Was wondering if all their fluctuating would be picked up... not necessarily in a dangerous way, but just in any noticable way.

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Re: CRT RGB Modification/Hack [56K Warning]

Post by Shadow » February 3rd, 2020, 12:58 pm

Okay, 5 years later (03/FEB/2020) and I was looking into this again and doing some thinking (because I want to finish the TV off), and it seems I need to build a "frequency doubler" or "frequency multiplier" circuit. The problem isn't the voltage levels because the transistors will 'turn on' at even 2V.

So, the problem is infact that the frequency is too low. The guns are not firing quickly which results in a dim picture. The faster the guns fire, the brighter the image will be because the phosphor coating will retail illumination for a longer duration :)

If I had a 'signal generator' then I could actually test this theory, so I might pick on up to confirm this before I start building a circuit. Then, if my theory is correct I will get around to doing some tests and seeing what type of circuit will suffice nicely for this application :mrgreen:
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Re: CRT RGB Modification/Hack [56K Warning]

Post by Shadow » February 7th, 2020, 6:27 pm

Okay, I am totally incorrect. I hooked up the signal generator and it is not the frequency which drives the contrast/brightness. It is in fact the amplitude of the signal. So, I'll need to build an amplification circuit which takes RGB in and feeds a higher amplitude out for each channel (IE: red, green and blue).

Notes to consider:
- Need to add potentiometers so each channel is driven independently for fine colour tuning.
- Need to add a voltage limiter on each channel to stop the transistor and electron guns from burning out.
- Should have small, telephony 1:1 winding transformers on each channel for complete isolation.
- Should have diodes on each channel for reverse current protection.
Development Console: SCPH-5502 with 8MB RAM, MM3 Modchip, PAL 60 Colour Modification (for NTSC), PSIO Switch Board, DB-9 breakout headers for both RGB and Serial output and an Xplorer with CAETLA 0.34.

PlayStation Development PC: Windows 98 SE, Pentium 3 at 400MHz, 128MB SDRAM, DTL-H2000, DTL-H2010, DTL-H201A, DTL-S2020 (with 4GB SCSI-2 HDD), 21" Sony G420, CD-R burner, 3.25" and 5.25" Floppy Diskette Drives, ZIP 100 Diskette Drive and an IBM Model M keyboard.

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Re: CRT RGB Modification/Hack [56K Warning]

Post by causeofdeath » March 30th, 2020, 3:34 pm

@Shadow: But your TV was originally supporting 15 kHz hsync ?

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Re: CRT RGB Modification/Hack [56K Warning]

Post by Shadow » March 30th, 2020, 6:04 pm

causeofdeath wrote:
March 30th, 2020, 3:34 pm
@Shadow: But your TV was originally supporting 15 kHz hsync ?
Yes, well 14.4 KHz to be exact (according to my old scope) but it's most likely 15 KHz :)
Development Console: SCPH-5502 with 8MB RAM, MM3 Modchip, PAL 60 Colour Modification (for NTSC), PSIO Switch Board, DB-9 breakout headers for both RGB and Serial output and an Xplorer with CAETLA 0.34.

PlayStation Development PC: Windows 98 SE, Pentium 3 at 400MHz, 128MB SDRAM, DTL-H2000, DTL-H2010, DTL-H201A, DTL-S2020 (with 4GB SCSI-2 HDD), 21" Sony G420, CD-R burner, 3.25" and 5.25" Floppy Diskette Drives, ZIP 100 Diskette Drive and an IBM Model M keyboard.

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Re: CRT RGB Modification/Hack [56K Warning]

Post by causeofdeath » April 13th, 2020, 8:16 am

@Shadow I had got one of these chinese GBS-8200 video upscaler units. Haven't gotten around to wiring it just yet, but the posts on various retrocomputing forums are positive.
https://cdn.shopify.com/s/files/1/0008/ ... Manual.pdf

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Re: CRT RGB Modification/Hack [56K Warning]

Post by Shadow » April 30th, 2020, 7:18 am

Okay, new update!

I tried building an op-amp circuit using an LM324. I also built a negative voltage supply for the op-amp but overall this did not work as intended.
Image

Next, I tried using the 'Ultimarc VGA' booster. Same principal. It uses an op-amp (much different to the LM324 however) but this performed the same (it would just increase the voltage to the guns but not amplify the signal correctly).

So after a few hours of testing and diagnosing, I finally found that the neck board has small pull down resistors on each gun. They were rated at 330R. After using a potentiometer to do some testing, I came to the conclusion to replace all three of them with 200R. I will be adding pots in line with these so that I can fine tune each of the red, green and blue signals intensity :)
Image

Finally, I had a strong intensity RGB signal. Here is a before and after. Notice how the intensity is very weak and the gradient at the bottom of each signal is weak. Also, don't worry, the red intensity is very strong. The camera settings are just different from the before photo.
Image

Yes, I know, I need to clean the glass. I had tape on the screen to protect it while it was in storage for a few years. I will be sanding the plastic down and painting it a nice matt black finish (with a semi-gloss clear coat to protect the paint).

More updates along the way as the project progresses :)
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Development Console: SCPH-5502 with 8MB RAM, MM3 Modchip, PAL 60 Colour Modification (for NTSC), PSIO Switch Board, DB-9 breakout headers for both RGB and Serial output and an Xplorer with CAETLA 0.34.

PlayStation Development PC: Windows 98 SE, Pentium 3 at 400MHz, 128MB SDRAM, DTL-H2000, DTL-H2010, DTL-H201A, DTL-S2020 (with 4GB SCSI-2 HDD), 21" Sony G420, CD-R burner, 3.25" and 5.25" Floppy Diskette Drives, ZIP 100 Diskette Drive and an IBM Model M keyboard.

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Re: CRT RGB Modification/Hack [56K Warning]

Post by Aura » April 30th, 2020, 11:05 am

Nice work

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Re: CRT RGB Modification/Hack [56K Warning]

Post by CosmoGuy » June 10th, 2020, 10:01 pm

Incredible how adding a simple op-amp circuit did increase color burst but didn't make image worse.
I'd presume that it could be to bright or to much of a contrast.
Image

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Re: CRT RGB Modification/Hack [56K Warning]

Post by Shadow » June 11th, 2020, 11:34 pm

CosmoGuy wrote:
June 10th, 2020, 10:01 pm
Incredible how adding a simple op-amp circuit did increase color burst but didn't make image worse.
I'd presume that it could be to bright or to much of a contrast.
The operational amplifier circuit did not work. I didn't use it.
Development Console: SCPH-5502 with 8MB RAM, MM3 Modchip, PAL 60 Colour Modification (for NTSC), PSIO Switch Board, DB-9 breakout headers for both RGB and Serial output and an Xplorer with CAETLA 0.34.

PlayStation Development PC: Windows 98 SE, Pentium 3 at 400MHz, 128MB SDRAM, DTL-H2000, DTL-H2010, DTL-H201A, DTL-S2020 (with 4GB SCSI-2 HDD), 21" Sony G420, CD-R burner, 3.25" and 5.25" Floppy Diskette Drives, ZIP 100 Diskette Drive and an IBM Model M keyboard.

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