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 Post subject: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Fri Sep 17, 2021 12:48 am 


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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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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Sun Sep 19, 2021 1:40 am 


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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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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Sun Sep 19, 2021 1:10 pm 


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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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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Wed Sep 22, 2021 1:17 am 



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From what I can see it is a Chassis CTC176F. Hope that helps your search.
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OSD/External RGB Mux Diagram
OSD/External RGB Mux Resistor Value Table 0.7Vp-p : 0.5Vp-p

"Imagine toggle switch OSD modding a TV in 2019" - maxtherabbit


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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Wed Sep 22, 2021 10:22 am 


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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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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Wed Sep 22, 2021 12:02 pm 



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Ok, looks like there might be a sams photofact for that chassis. Might have to pay.
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OSD/External RGB Mux Diagram
OSD/External RGB Mux Resistor Value Table 0.7Vp-p : 0.5Vp-p

"Imagine toggle switch OSD modding a TV in 2019" - maxtherabbit


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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Wed Sep 22, 2021 3:03 pm 


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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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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Thu Sep 23, 2021 11:29 am 



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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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MarkOZLAD
OSD/External RGB Mux Diagram
OSD/External RGB Mux Resistor Value Table 0.7Vp-p : 0.5Vp-p

"Imagine toggle switch OSD modding a TV in 2019" - maxtherabbit


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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Thu Sep 23, 2021 11:38 am 


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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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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Thu Sep 23, 2021 11:45 am 


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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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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Thu Sep 30, 2021 6:04 pm 


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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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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Sat Oct 02, 2021 2:02 am 


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Shotty CRT discharging tool! If I don't respond within a month, I'm probably dead. :lol:

Spoiler: show
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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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Sat Oct 02, 2021 6:37 pm 


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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.
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Last edited by DotMatrixMoe on Sun Oct 03, 2021 2:49 pm, edited 1 time in total.

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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Sun Oct 03, 2021 2:15 am 


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

Spoiler: show
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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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Tue Oct 05, 2021 7:17 pm 


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Parts are almost here! Woot woot!
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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Thu Oct 07, 2021 10:48 pm 


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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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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Thu Oct 07, 2021 10:53 pm 


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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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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Fri Oct 08, 2021 11:42 am 


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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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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Sat Oct 09, 2021 3:05 am 


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

Spoiler: show
Image

Image

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

Spoiler: show
Image

Image


And after some shimming, the PCB:
Spoiler: show
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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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Sat Oct 09, 2021 3:57 am 


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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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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Sun Oct 10, 2021 4:45 pm 


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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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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Sun Oct 10, 2021 6:03 pm 


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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.

Image
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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Sun Oct 10, 2021 11:25 pm 


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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.

Image
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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Mon Oct 11, 2021 2:45 am 


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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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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Tue Oct 12, 2021 12:16 am 



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Most of the pictures aren't showing for me.
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OSD/External RGB Mux Diagram
OSD/External RGB Mux Resistor Value Table 0.7Vp-p : 0.5Vp-p

"Imagine toggle switch OSD modding a TV in 2019" - maxtherabbit


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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Tue Oct 12, 2021 12:41 am 


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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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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Tue Oct 12, 2021 3:58 am 


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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


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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Tue Oct 12, 2021 8:43 am 



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I would expect U1001 to be jungle, U3100 to be micom (if you haven't already worked that out...)
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OSD/External RGB Mux Diagram
OSD/External RGB Mux Resistor Value Table 0.7Vp-p : 0.5Vp-p

"Imagine toggle switch OSD modding a TV in 2019" - maxtherabbit


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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Tue Oct 12, 2021 9:51 am 


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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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 Post subject: Re: Can GE 20GT612 Be Fitted With RGB Mod?
PostPosted: Tue Oct 12, 2021 9:58 am 


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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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