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CRT TV EEPROM & Micom hacking for RGB (+tube swap for 48cm to 51cm TV)


buttersoft

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This thread started out being about swapping a 48cm tube onto a chassis that originally had a 51cm tube, but has turned into a discussion of EEPROM and microcontroller hacking to enable RGB on old Australian (possibly NZ) SD CRT TV's on which it appears to have been disabled by the microcontroller (Micom). Discussion of the latter begins a few pages in, and it's all very much a work in progress.

 

Note that not all old sets need the above, in progress hack in order for you to RGB mod them. As a very rough guide, if the neckboard has colour pots for RGB bias/gain, you probably don't need to worry, injecting signals into the jungle IC should just work. For newer sets without neckboard pots, try inserting RGB, and see if it works.

 

Remember that the shumps thread is a better place for information on the subject of RGB hacking!

 

I've been hunting for more RGB-moddable chassis to drive 20"/48cm TV tubes - the standard 2ohm/14.8ohm ones in old cabs. They're getting harder to find though.

 

After @namastepat's just-make-it-fit suggestion I was wondering about swapping out the chassis from a 51cm TV and using it on a standard 48cm tube. Do the 51cm tubes typically have the same yoke resistances and pinout? Is the required HV going to be much different? I know I've seen chassis that will suit multiple tubes.

 

At the moment I'm looking at this job here - https://my.mixtape.moe/rnatkf.pdf.

 

That service manual says the chassis can handle 14", 20" and 21" tubes. (In this particular case I suspect the 20" and 21" tubes might be the same thing but US vs Aus names? i.e both the same 51cm tube, not a 48cm one?)

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For the record, I have made enquiries with LG part sellers and they say that LG no longer supply the PJ201 Scart Jack and there is no equivalent part available from them. Will have little choice but to go with @NEO-GEO 's suggestion.

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For the record, I have made enquiries with LG part sellers and they say that LG no longer supply the PJ201 Scart Jack and there is no equivalent part available from them. Will have little choice but to go with @NEO-GEO 's suggestion.

 

Youll likely find that item will fit fine anyway, theyre generally pretty standard.

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Nice job! Here's hoping it all runs smoothly, but i reckon it will from this point.

 

This is kinda what modding TV's for RGB is about. Sometimes you have to do more than just connect up a few wires, and sometimes there's a better way around to begin with.

 

When you have it up and running you should make a mod log and post it up in the shmups thread. This is important info :)

 

It's a shame that you never tapped into the EEPROM directly, I'd have liked before and afters of the code. But like hell anyone would bother when you could just use the remote :)

 

Cheers,

 

Thanks for the help and encouragement along the way. I learned so much during the process and whilst the solution appears simple in this case I wouldn't have solved it without going through the process. Had never looked at a TV service manual or schematic before.

 

I will do a post on SHMUPS thread when I can. Seems any LG with the MC-84A chassis is now a no brainer for this procedure and might help bring to life a heap of previously useless sets and help build/rejuvenate some arcade cabs cheaply. It might be worth looking through the specs on other LG chassis to see if they are similarly simple to mod.

 

Here is a list of LG models and chassis....

 

https://drive.google.com/open?id=0BxXDEFhRZ50MTmpINVVfQnNNOFU

 

- - - Updated - - -

 

Youll likely find that item will fit fine anyway, theyre generally pretty standard.

 

It was more out of interest than anything.

 

- - - Updated - - -

 

Nope. I used to think they were bias voltages but I'm guessing there's no way you'll get anything near that if you measure the DC voltage at those points. I'd be interested to find out what they mean.

 

It seems they are voltages of some sort.

 

IC Voltages.png

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It seems they are voltages of some sort.

 

No need to be cryptic :) What sort of voltages are they?

 

I've found sometimes they are, but in some cases they're so far out and all in different directions i'm not sure what I'm looking at.

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Shmups thread can be found here:

 

http://shmups.system11.org/viewtopic.php?t=60010

 

Hah, i meant in the regular RGB mod thread i keep linking to - http://shmups.system11.org/viewtopic.php?f=6&t=56155 - that's the main repository. Can you make a link to that thread in your post on there, and vice versa? With a quick precis about simply turning RGB on in the service menu, i 'd say. I'm happy to do it, if you don't want to. That way people can find what you've done. Even getting as far as you have is an important step!

 

Great writeup, too :)

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Have compiled an excel spreadsheet to list LG Chassis and Model numbers to try and help people identify model numbers that are easy to mod to Scart. It's not exhaustive and there are likely errors. Message me if you find out a chassis/model is moddable and I'll modify the lists.

 

https://drive.google.com/open?id=0BxXDEFhRZ50MSXoyb01PN3hGdUE

 

The only true way to be sure is to find the service manual/schematic for the model you are looking at and inspect it. A way to find the chassis number for your model is to find a spare parts list for the TV by model. For example for this model we can see the spare chassis is the 84A http://spares.bigwarehouse.com.au/index.php?cPath=24759_24766_25883

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Bet ya glad you did that instead of buying something else ;)

 

Yeah, I was just interested in the options.

 

Turns out there weren't any other credible options anyway.

 

This piece attached to the chassis like it came that way from the factory. Only problem is the rear AV panel needing modification.

 

 

Sent from my iPhone using Aussie Arcade

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Chassis swap (51cm to 48cm tube) + MarkOZLAD's RGB SCART hack for LG TVs

 

Jamma to Scart adapter.

 

I have one of these:

 

https://www.ebay.com.au/itm/322544727766

 

But it is destined for a different machine.

 

There are these, much cheaper.

 

https://www.ebay.com.au/itm/152243258281

 

Or I might investigate building my own. Plenty of Jamma to Scart instructions online.

 

http://www.gameland.gr/geoanas/realarcade.htm

 

 

Sent from my iPhone using Aussie Arcade

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