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Help with CRT TV connection to original game PCB's


Strahany

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Hey guys, I know this topic will definitely have been covered at some point in the past here but I have not been able to find it so if anybody could please enlighten me as to where to find it that would be awesome.

I have a Sony Trinitron CRT TV (model# KV-XA25M31) which is pretty much the last of their 4:3 aspect CRT's and was wanting to make the grand daddy of cocktail cabs out of it, I have several original game boards from the 80's and have purchased a 6 way JAMMA switcher so I can have 6 of my favorite original games in one awesome cabinet. My question is can I connect the RGB signal direct from the JAMMA pinouts to the component input on the Sony, obviously there is no sync input on the Sony so I am assuming that I will either need some form of converter or this is a bigger project than first thought. I originally had these boards running on a proper commercial arcade machine years ago and have since sold it so the boards have been in safe storage for around 20 years. I have bought a few of the different multi boards (60 in 1, pandoras box styles etc...) and these are ok but they don't play EXACTLY the way the originals did, in particular I cannot find a nice version of GYRUSS.

But as luck has it I still have my original GYRUSS board and would love to get this especially (along with others) up and running on a CRT based cocktail cab, the Sony TV I have was bought from new by me and hasn't done much work until put into storage and I figured it would be great as it is nice and bright and clear but should still retain that analog charm.

Anyway if anybody has any suggestions or can point me to some helpful threads I would be most grateful.

Cheers and game on!!!

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The only issue you will have with your approach is that the teletext RGB shares the RGB lines of the OSD. The OSD lines have termination resistors on them R063, R064 and R065.

 

These will interact with any termination resistors you put on the external RGB and will make your external RGB have incorrect and/or your OSD voltages wrong.

 

 

Sent from my iPhone using Aussie Arcade

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Otherwise you can remove R063-065 and put 620 ohm in line resistors on the external RGB lines, to go with the normal 75R.

 

You would then be doing a mux

 

 

Sent from my iPhone using Aussie Arcade

 

 

Do you know what the output voltage of the teletext chip's RGB is?

 

- - - Updated - - -

 

If you use 91 ohm termination on your external RGB you should get close to the required 75ohm (because of the inbuilt 470R) but the OSD will be washed out.

 

 

Sent from my iPhone using Aussie Arcade

When i read through your thread on shumps i cant see anywhere that you say you did that, just that you fed into CN307 and it worked straight up? Was there more work you did there that is not mensioned in that thread?

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If you use 91 ohm termination on your external RGB you should get close to the required 75ohm (because of the inbuilt 470R) but the OSD will be washed out.

 

 

Sent from my iPhone using Aussie Arcade

 

 

One other question about this;

 

WHY are you terminating 75ohm to ground and not just putting the appropriate size resistor in line to drop the level?

 

Im sure there is a reason, but id expect if you drop the voltage using an in line resistor instead of terminations to ground, everything should stay the same and it should all work fine?

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My post on SHMUPS was from early in my journey and hasn’t been updated.

 

75R to ground is standard analog video termination.

 

 

Sent from my iPhone using Aussie Arcade

 

Yeah i know it is, but what stops us using inline resistors?

 

This should theoretically produce a good result yes?

 

Have you looked into using the INT RGB pins on the jungle with the BG3R?

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Weird, I’ve used teletext to blank before. These was on a BG3S

 

 

Sent from my iPhone using Aussie Arcade

Yeah mate its odd isnt it, but once you get a source in there pressing the teletext does nothing at all.

 

I used 100ohm resistors through a switch.

 

I took 5v from the 7805 reg, put that through a switch and that does the job. The image is fantastic, but for some reason ive got no audio. Ill have to open it up another day.

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Weird, I’ve used teletext to blank before. These was on a BG3S

 

 

Sent from my iPhone using Aussie Arcade

 

Ok, so no question about it, the teletext button wont do blank, but thats fine.

 

Fixed the audio, but ive only got left speaker.

 

What i might do is remove from composite 1 and use the component input for sunc and audio instead, do you know of any issues doing that Mark?

 

Im going to need to change those resistors, 100ohm is not enough really. Might drop down to somewhere near 85ohm.

 

Ive fixed the off-center image, it is now centered nicely.

 

- - - Updated - - -

 

For those who dont know, parallel resistors will ALWAYS lower resistance:

 

1/r1 +1/r2 + 1/r3 = total resistance.

 

I add this because i saw on Shmups someone was saying saying something totally different which will give a completely wrong value.

 

Easy enough trap to fall into, but giving current an extra path to flow down cant ever result in a higher resistance than the lowest value path, any added parallel resistor will always result in LOWER overall resistance.

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It’s generally fine to use component input for sync and audio.

 

I have heard of an issue where the TV’s component board had bad caps and that meant the TV had trouble syncing through there. If the caps are fine should work perfectly.

 

 

Sent from my iPhone using Aussie Arcade

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It’s generally fine to use component input for sync and audio.

 

I have heard of an issue where the TV’s component board had bad caps and that meant the TV had trouble syncing through there. If the caps are fine should work perfectly.

 

.

Sent from my iPhone using Aussie Arcade

Oh i know it works ive tested it ;) Just wondering if you were aware of it causing any issues

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It’s generally fine to use component input for sync and audio.

 

I have heard of an issue where the TV’s component board had bad caps and that meant the TV had trouble syncing through there. If the caps are fine should work perfectly.

 

 

Sent from my iPhone using Aussie Arcade

Dont know why but my posts dont show up on Shmups, is there no admin on that site or whats the go there mate?

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If you're a new member, your first post is moderated / reviewed before being published. Can take a day or two. Once confirmed legit (not spam / a robot / a dickhead etc) it and all subsequent posts will be published.

 

Yeah but this is 2 weeks later and still nothing!

 

- - - Updated - - -

 

So that’s why I miss posts? Was wondering why new stuff shows up five messages ago.

 

 

Sent from my iPhone using Aussie Arcade

 

Have you seen any from me? Can you please send the admin a PM and let them know i still cant post?

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