RGB from Neckboard

[spikespiegel]

I'm trying to MOD RGB a CRT but I have some questions about this diagram (picture). Does this 1N4148 need to be a zener diode? Can it be replaced by an equivalent diode? How do I find out which one is equivalent?
About the resistor 820: I will use 3 potentiometers of 1k each, so do I really need to use this resistor 820 too?
About c-sync, should it be connected to the AV (composite) in or somewhere else? If yes, should I use it in the positive or gnd connector?

[Syntax]

Thats not how we do things around here...

You won't get any help for a neckboard mod, they suck.

If you have component input then use a converter, if not then rgb mod the chassis.

[spikespiegel]

Thats not how we do things around here...

You won't get any help for a neckboard mod, they suck.

If you have component input then use a converter, if not then rgb mod the chassis.

There's no way to use the chassis for this mod (It's not possible). I really want to use the neckboard, not the component-in, so leave it to me to decide if I'm going to like it or not, same way no one is forced to help me with this, but any help would be appreciated, so please don't ruin my chances of getting actual help.

[Osirus]

1N4148 doesn't look like a zener diode.

Connect sync to composite input. Connecting it to ground would just.. ground out the signal.

[spikespiegel]

1N4148 doesn't look like a zener diode.

Connect sync to composite input. Connecting it to ground would just.. ground out the signal.

Is there any equivalent diode to 1N4148?

[Syntax]

You have 0 control over clamping and heaps of other important stuff going neckboard over component, and there is 0 difference between using rgb and component via a good converter.

Else have fun wasting time making a crap picture just so you can say your tv does RGB.

[spikespiegel]

You have 0 control over clamping and heaps of other important stuff going neckboard over component, and there is 0 difference between using rgb and component via a good converter.

Else have fun wasting time making a crap picture just so you can say your tv does RGB.

Cool. So long.

[Osirus]

1N4148 doesn't look like a zener diode.

Connect sync to composite input. Connecting it to ground would just.. ground out the signal.

Is there any equivalent diode to 1N4148?

I dunno. Doesn't seem hard to come by. Mouser has 500k in stock.

That's just for the sync combiner though. There are many other ways of combining sync. I do this: https://www.retrorgb.com/building-a-pas ... biner.html

[spikespiegel]

This one looks interesting. Do you use it with VGA?

[Osirus]

You could use it with a DE-15 connector yes.

[spikespiegel]

You could use it with a DE-15 connector yes.

Why aren't any capacitors being used in the RGB cable? I was informed that they're important to avoid electrical discharge.

[lukilla]

I´ve been using the dodgy diode circuit for years, it works great but you need to make sure that both of the syncs are negative:

http://members.optusnet.com.au/eviltim/scart.htm

As for going to the neckboard, I have done it on a few tv´s so I can tell you that you will need to build an rgb amplifier in order to get some control over the bias and gain of the signals, because video is not standard over there. Without any way to tweak those things, it´s gonna look ranging from horrible to no usable picture at all. Also you will want to build a linear power supply or you are gonna get noise. An OSD mod is a walk in the park in comparison.

[spikespiegel]

I´ve been using the dodgy diode circuit for years, it works great but you need to make sure that both of the syncs are negative:

http://members.optusnet.com.au/eviltim/scart.htm

As for going to the neckboard, I have done it on a few tv´s so I can tell you that you will need to build an rgb amplifier in order to get some control over the bias and gain of the signals, because video is not standard over there. Without any way to tweak those things, it´s gonna look ranging from horrible to no usable picture at all. Also you will want to build a linear power supply or you are gonna get noise. An OSD mod is a walk in the park in comparison.

I forgot to mention, this application is just for vga signal, like using a computer or a raspberry pi.

[lukilla]

I´ve been using the dodgy diode circuit for years, it works great but you need to make sure that both of the syncs are negative:

http://members.optusnet.com.au/eviltim/scart.htm

As for going to the neckboard, I have done it on a few tv´s so I can tell you that you will need to build an rgb amplifier in order to get some control over the bias and gain of the signals, because video is not standard over there. Without any way to tweak those things, it´s gonna look ranging from horrible to no usable picture at all. Also you will want to build a linear power supply or you are gonna get noise. An OSD mod is a walk in the park in comparison.

I forgot to mention, this application is just for vga signal, like using a computer or a raspberry pi.

I do it using a vga signal, a console signal would be more complicated since the black level is not clamped. All in all, if you do it for image quality and you have to go to neckboard for some reason, there is no way around an amplifier since vga is too weak to drive it and you need to tweak each color line.

[KPackratt2k]

Thats not how we do things around here...

You won't get any help for a neckboard mod, they suck.

If you have component input then use a converter, if not then rgb mod the chassis.

But what about sets without Component inputs that can't be RGB modded any other way than the neckboard? I've come across a few sets where this is the case (either they have digital RGB inputs only or they're just too old to have one at all on the jungle chip).

[Syntax]

You find another TV.
No one with a decent set of eyes neck mods a TV and is happy with the result.

[spikespiegel]

A friend tried with an amplifier and it worked flawlessly:

[KPackratt2k]

You find another TV.
No one with a decent set of eyes neck mods a TV and is happy with the result.

Sorry, but as CRT TVs are becoming harder to find nowadays without having to resort to paying $$$ to scalpers (and for some people, are already impossible to find), a lot of people are stuck with what they have, and for some people (including at least one other member of this forum) it may be a TV that's too old to have a jungle chip with any usable RGB inputs unfortunately. Sure, you may be able to at least mod such sets for S-Video, but honestly, once you see (and experience) RGB, it's really hard to go back, so for those people, S-Video really isn't cutting it anymore (Heck, some people have even labeled it as "garbage quality" compared to RGB).

As CRT TVs with modifiable jungle chips are becoming harder to find, I think it'll eventually become important to research ways to RGB neckboard mod these older sets so that a lot more TVs are open to being RGB modifiable. I think we should appreciate what we have instead of just saying "nah" and resort to wasting time finding something that may never come up for sale in their area, because some of us really are stuck with what we have, even if it's something like a crappy old '80s TV with no RGB capable jungle chip.

[Syntax]

If you are that desperate to use a tube that has a chassis which does not support the video mode you desire then buy a chassis that does and fit that.

The results will be far better than any neckboard mod and cheaper too.

https://www.aliexpress.com/item/526651150.html