Adding Potentiometer to CRT Chassis for Vert Size Adjustment

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darknezz19
Posts: 60
Joined: Tue Oct 13, 2015 1:59 am

Adding Potentiometer to CRT Chassis for Vert Size Adjustment

Post by darknezz19 »

Want to mod a home crt chassis that is in a groovymame arcade with a vertical potentiometer. Too much hassle to get into service menu each time it needs resizing. Would adjusting R551 on pin 22 accomplish this?

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darknezz19
Posts: 60
Joined: Tue Oct 13, 2015 1:59 am

Re: Adding Potentiometer to CRT Chassis for Vert Size Adjust

Post by darknezz19 »

So ditched this idea because was afraid of messing with the Xray safety circuit. Got an ardiuno and downloaded one of Martin Hejnfelt's i2c projects to enable rgb on certain jungles. The git is below.

https://github.com/skumlos/tb1226en-i2c-bridge

My Jungle is a TA1268N, uses the same write address and read address as his jungle. Edited the code to just look for 09 offsets and edit the hex to change Vsize. Was having trouble getting it to work at first, but for some reason when my logic analyzer is hooked up to the i2c outputs that go to the jungle, it magically starts working. I'm not sure why yet, and need to figure that out. Edited the Vsize value manually and reuploaded to the ardiuno, Vsize was indeed changed. In the end my goal will to be to store an initial Vsize value, and then map a couple momentary switches to increase and decrease the value.

This will be great for GroovyMame setups. As many of your might already know, most all other geometry can be controlled with settings in the driver, except for Vsize. When this is done, which might take a while longer as I'm a green horn with C++, should be seamless to change that setting. No more having to go through the service menu when changing a game.

Big thanks to Martin for making his code open source, couldn't have started this without his initial code.

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darknezz19
Posts: 60
Joined: Tue Oct 13, 2015 1:59 am

Re: Adding Potentiometer to CRT Chassis for Vert Size Adjust

Post by darknezz19 »

Got it working for the most part.

https://www.youtube.com/shorts/iaNxtEacty4

Here is a fork with Martin's original code and the edit's for Vsize.

https://github.com/darknezz19/tb1226en-vsize-bridge
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Gunstar
Posts: 617
Joined: Wed Apr 09, 2014 10:29 am
Location: UK

Re: Adding Potentiometer to CRT Chassis for Vert Size Adjust

Post by Gunstar »

Nice work! it goes over my head but it sounds like a really handy feature to have
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BazookaBen
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Joined: Thu Apr 17, 2008 8:09 pm
Location: North Carolina

Re: Adding Potentiometer to CRT Chassis for Vert Size Adjust

Post by BazookaBen »

Yo that's amazing man!

This would be super useful for modern 240p games, since they're almost all 16:9.

Like if you're running a CRT Emudriver setup and want to play Shovel Knight, for example.
Johngalindo
Posts: 2
Joined: Fri Dec 09, 2022 10:27 am

Re: Adding Potentiometer to CRT Chassis for Vert Size Adjust

Post by Johngalindo »

This allows adjusting geometry between games in a very convenient way. He's installed 3 potentiometers: V-SIZE, H-SIZE, and H-SHIFT. crt chassis that is in a groovymame arcade with a vertical potentiometer. Too much hassle to get into service menu each time.
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