Can GE 20GT612 Be Fitted With RGB Mod?

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DotMatrixMoe
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Can GE 20GT612 Be Fitted With RGB Mod?

Post by DotMatrixMoe »

Hello, I own a television from General Electronics, given to me for free by my neighbor. I've had it for a year now, and love the aesthetic of the wood grain :lol:

I've done my research on "Jungle" IC chips and several examples of the RGB mod. But, I've yet to find a service manual on my CRT. I don't want to just open it blindly, I prefer operating with a plan. Perhaps does anyone know if it's even possible to RGB mod a TV this fairly old?

--------------------------------------------
Info:
2 Composite signals
3 Audio In and 1 Audio Out
RF Jack
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DotMatrixMoe
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

Post by DotMatrixMoe »

Here's some pictures that might clear things up. A correction to my first post, there's 2 outputs and 2 inputs, not 1 output. The 2nd output doesn't seem to work in my knowledge, but the 1st one outputs all of the TV's sound (Both RF and Composite).
https://imgur.com/a/feBABo2
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

Post by DotMatrixMoe »

I've discovered muxing on another thread. Basically utilizing the RGB blanking pin on SCART to automatically display the signal on connection.

Image

However, I've yet to check if I have inline resistors to the OSD chip. I might have to check to see if the television is even RGB modifiable manually, which I'm not too thrilled about.

I suspect it has a OSD micro controller and Jungle IC for sure, lets pray.
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

Post by MarkOZLAD »

From what I can see it is a Chassis CTC176F. Hope that helps your search.
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

Post by DotMatrixMoe »

MarkOZLAD wrote:From what I can see it is a Chassis CTC176F. Hope that helps your search.
From the back of my TV, it looks like a CTC148P (Chassis). Know any good websites? Looking for service manuals are a headache :lol:
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

Post by MarkOZLAD »

Ok, looks like there might be a sams photofact for that chassis. Might have to pay.
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

Post by DotMatrixMoe »

MarkOZLAD wrote:Ok, looks like there might be a sams photofact for that chassis. Might have to pay.
Ah bummer, and it's a whole $30. A bit much for a service manual. I might continue considering checking manually, the project itself is fairly expensive:

- Dremel
- Wire stripper and crimper (Mine broke).
- Alligator clips, to discharge the CRT.
- Resistors
- And lastly, the SCART socket itself.

Can you sell kidneys on this forum? :P
Someone offered to get me some of the parts, so maybe I need to sell half of one.
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

Post by MarkOZLAD »

When I can’t find a schematic I inspect all the chips on the chassis and write down the model numbers. I then look up the data sheets.

If I determine that the jungle chip has RGB inputs I photograph the top and underside of the chassis and blow up the images on my pc to trace out the RGB and blanking circuits. I also try and find a 5V source. Ground is all over the place.

Once I find the circuits I try and ascertain what resistors and caps are in place either using the colour codes, multimeter or capacitor codes.

After I’ve done all that I design my mod.
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

Post by DotMatrixMoe »

MarkOZLAD wrote:When I can’t find a schematic I inspect all the chips on the chassis and write down the model numbers. I then look up the data sheets.

If I determine that the jungle chip has RGB inputs I photograph the top and underside of the chassis and blow up the images on my pc to trace out the RGB and blanking circuits. I also try and find a 5V source. Ground is all over the place.

Once I find the circuits I try and ascertain what resistors and caps are in place either using the colour codes, multimeter or capacitor codes.

After I’ve done all that I design my mod.
That's a pretty neat idea, probably more common than the chassis itself. I'll try that... once my alligator clips arrive. Don't want to BDF mod myself. (Be Dead Forever)
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

Post by DotMatrixMoe »

I have a question on the mod however. I understand the circuit but where the ground should go. Should they be in the same ground?

Oh, and one amateur question... do I lead the RGB lines both to the SCART pins and lead them to ground, or is that a death sentence.
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

Post by DotMatrixMoe »

DotMatrixMoe wrote:I have a question on the mod however. I understand the circuit but where the ground should go. Should they be in the same ground?

Oh, and one amateur question... do I lead the RGB lines both to the SCART pins and lead them to ground, or is that a death sentence.
Haven't replied for a while, I answered that question for myself. At this point, I'm currently awaiting the parts needed to do the mod. I also plan on recording it, as a reference for myself and maybe others as well. As for this forum, it's now my build log.
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

Post by DotMatrixMoe »

Shotty CRT discharging tool! If I don't respond within a month, I'm probably dead. :lol:
Spoiler
Image
Welp, maybe in a week or two... I'm going to open the wood grain beauty and check the model number of the jungle chip.
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

Post by DotMatrixMoe »

Speaking of taking it apart, it seems that I need a slightly bigger socket wrench than I thought. When my dad comes around, I'll ask to borrow it for a bit.
Last edited by DotMatrixMoe on Sun Oct 03, 2021 2:49 pm, edited 1 time in total.
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

Post by DotMatrixMoe »

Leaving some before pictures here. I'll revisit these once I complete the mod, and give my overall view on it.
Spoiler
Image

Image

Image
All in composite, output from PC. Cannot wait to see the difference!
(You can even see the offsetting blur and pale color.)
Excuse my thumb... :oops:
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

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Parts are almost here! Woot woot!
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

Post by DotMatrixMoe »

Though my dad is going to visit tomorrow and get me the nutdriver I need, I had a sneak peak though the vents and saw that a mini service manual is in there. A diagram of the motherboard and get this, model numbers for all the chips. It's in small text, and seeing through the vent is hard. So once I take it apart, I'll take a picture of it, upload it, and use it to design my mod.
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

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DotMatrixMoe wrote:Though my dad is going to visit tomorrow and get me the nutdriver I need, I had a sneak peak though the vents and saw that a mini service manual is in there. A diagram of the motherboard and get this, model numbers for all the chips. It's in small text, and seeing through the vent is hard. So once I take it apart, I'll take a picture of it, upload it, and use it to design my mod.


I would've taken a picture that can at least prove it's there, but it'd look like a Super Smash Bros. leak.
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

Post by DotMatrixMoe »

Dad will be able to come by in 3:00pm. Cannot wait! I'm making a mostly visual schematic on the mod, so RCA and GE television owners with the same chassis can lay back and save the research for me.
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

Post by DotMatrixMoe »

I finally got the thing disassembled and wasn't lying about the mini service manual!
Spoiler
Image

Image
And most importantly, I didn't die from the anode cap!
Spoiler
Image

Image
And after some shimming, the PCB:
Spoiler
Image
While I wanted to take a picture of the front of the PCB as well...
Unfortunately the IF shielding is soldered on. (Obviously I have a soldering iron, I just don't feel like it after the hassle I went through.) Conveniently I know that the OSD is under the shielding because the it seems to be marked. I didn't take a photo, but looking at the bottom of the PCB convinced me.

The two composite inputs are annoying as well, it's unclear through a multimeter which pin they use. But for audio, I was able to locate ground and the signal itself.

Once I get the shielding off, I'll write down it's modes of both the Jungle and OSD chipsl and mark the pins I'm using for the mux circuit. As you can see, I'm already getting started on the diagram:

Image

All from GIMP haha! After 2 years of use, its awesome to use as a diagram maker.

Wish me luck!
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

Post by DotMatrixMoe »

On 2nd glance, I suspect the A23110001A might be the jungle chip. I'm looking for a datasheet, but man finding information on this chassis is hard!
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

Post by DotMatrixMoe »

So I found this site after many hours on my jungle chip.
https://precisionlogicinc.net/parts/a23110001a#pdf
They claim to have a datasheet on it, so I shot them an email. Hopefully I get a response.
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

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DotMatrixMoe wrote:So I found this site after many hours on my jungle chip.
https://precisionlogicinc.net/parts/a23110001a#pdf
They claim to have a datasheet on it, so I shot them an email. Hopefully I get a response.
Also, minor update on schematic. Just added the chroma chip and its model number.
Just to remind you, I made this chip from scratch using GIMP.

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Re: Can GE 20GT612 Be Fitted With RGB Mod?

Post by DotMatrixMoe »

BINGO! Found the model number of my OSD as well! Same situation as the chorma chip, contacting an IC chip manufacturer for the datasheet. Schematic is looking more complete, too.

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Re: Can GE 20GT612 Be Fitted With RGB Mod?

Post by DotMatrixMoe »

I might actually be wrong about the OSD. Looking into the mini service manual and PCB, it might be 1874-2UH.

TIme to do even more research. :roll:
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

Post by MarkOZLAD »

Most of the pictures aren't showing for me.
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

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MarkOZLAD wrote:Most of the pictures aren't showing for me.
Here's all the images I've used.
https://drive.google.com/drive/folders/ ... sp=sharing
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

Post by Syntax »

Jungle will have more than 28 pins.

Probably the one in the center of the board.

From what I can tell RCA reused a heap of tech in other models, might have luck with this.

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Re: Can GE 20GT612 Be Fitted With RGB Mod?

Post by MarkOZLAD »

I would expect U1001 to be jungle, U3100 to be micom (if you haven't already worked that out...)
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

Post by DotMatrixMoe »

MarkOZLAD wrote:I would expect U1001 to be jungle, U3100 to be micom (if you haven't already worked that out...)
Figured U1001 was the jungle chip, but was completely clueless on the OSD :lol:
Thanks a lot!
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Re: Can GE 20GT612 Be Fitted With RGB Mod?

Post by DotMatrixMoe »

Syntax wrote:Jungle will have more than 28 pins.

Probably the one in the center of the board.

From what I can tell RCA reused a heap of tech in other models, might have luck with this.

Image
Awesome, I'll confirm it by following the traces of the pins and write where the resistors are. This is useful, thanks.
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