PlayStation Development Network

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.

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

Okay, I am totally incorrect. I have since acquired more electronic test equipment and I hooked up my 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.
• Maybe have small 1:1 winding transformers on each channel for isolation (though, this might reduce the current considerably).
• Should have diodes on each channel for reverse current protection.

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

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

@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

Okay, new update! Now I'm really learning and getting things progressing

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.


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


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.


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 (which was a silly idea since now I need to clean it off the glass with alcohol carefully). I will also be wet sanding the plastic down and painting it a nice matte black finish (with a semi-gloss clear coat to protect the paint) afterwards instead of the ugly stock grey colour.

More updates along the way as the project progresses

Nice work

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.

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.

I've been lurking for months on your progress. Now, I have the guts to make an account and ask; have you done anything else with the TV? Because I can't inject signals via Jungle IC, I'm doing a similar mod. I'd also appreciate it if you showed how you wired the mod so far.

Thanks in advance!

I have done a lot more work on the TV. I designed a small circuit board which I have etched myself and the TV is working nicely. I will continue with the project when I have more free time and share the schematics eventually of the circuit I designed (as well as the code for the MCU). The last thing I started working on was using the channel up/down buttons to drive a digital potentiometer on the front of the TV to adjust the RGB power levels.

Don't worry, I will be getting a professional PCB made. The DIY board I made was to ditch the breadboard with all the spaghetti wires.

Wow Shadow! You did the tough version of a RGB mod. I RGB modded a TV recently myself. The TV has a Jungle IC with analog RGB OSD inputs so it was as simple as feeding RGB from external connectors into the right points on the board. I ended up pulling one leg of each capacitor for Red, Green, and Blue, and soldered wires from the board holes and capacitor legs to a switch.

The result was very good with the RGB signals terminated at 75ohms to ground.

I had always heard of people talking about RGB modding by driving the signals to the neck board directly but never saw anyone post about actually doing it. I'm sure all the trouble was worth it, RGB is such a fantastic improvement over composite video.

I've done the Jungle IC mod before and it works, but there is no varying RGB intensity in the contrast levels so I wasn't happy with it. The Jungle IC uses digital RGB where as the neck board mod will allow an analog RGB input which results in much nicer contrast levels on each red, green and blue colour index.

Every TV is different and not all of them are suitable for a Jungle IC RGB mod. Digital RGB OSD inputs are a no go from what I've seen people say in discussions. The TV I did mine on I got from a friend. Before I said I'd take it I asked them for the model number and after looking it up and determining that a Jungle IC based RGB mod was possible I said yes.

There is a project out there where someone is looking to make a universal chassis for CRTs. I think the goal is to only need the CRT (tube), the Yoke, and probably the Neck board. But it's a WIP project.

Anyway, I'm happy you have RGB input now. It's a night and day difference from Composite. Although PAL Composite might not be as bad as NTSC Composite.

MottZilla wrote: ↑February 26th, 2022, 6:02 pm Every TV is different and not all of them are suitable for a Jungle IC RGB mod. Digital RGB OSD inputs are a no go from what I've seen people say in discussions. The TV I did mine on I got from a friend. Before I said I'd take it I asked them for the model number and after looking it up and determining that a Jungle IC based RGB mod was possible I said yes.

There is a project out there where someone is looking to make a universal chassis for CRTs. I think the goal is to only need the CRT (tube), the Yoke, and probably the Neck board. But it's a WIP project.

Anyway, I'm happy you have RGB input now. It's a night and day difference from Composite. Although PAL Composite might not be as bad as NTSC Composite.

It'd be interested in the universal chassis. Usually the yoke is custom wound for the tube size so if they make a universal board which will have jumpers or better yet, a programmable way of setting things up (which means a huge database of TV's could be public which makes setting up the universal chassis settings for users easier) that can use the same yoke, that would be nice.

It was mentioned that most likely you'd have to tune things to the specific CRT and Yoke. But that you should probably be able to start somewhere in the ballpark and then dial things in.