8 Bit Guy CRT TV RGB Mod Log

[MarkOZLAD]

Here are some notes from my work to enable the 8 Bit Guy to RGB mod his little Samsung TV.

TV Model: Samsung TXD-1372
Chassis: K-1
Service Manual Link
Jungle chip is TA1201AN. Datasheet Link

8 Bit Guy Video 1 Video 2

After analysis of the schematics, the On Screen Display Circuit for this TV could be simplified to this.



This set was unusual, it has some extra circuitry for what I believe is for Close Caption Display. I might add a later post with more detail about it but, long story short, it appears that it was designed to be disabled in some versions of this set (the board and schematic show an optional jumper) so I decided we should bypass it with addition of the jumper JWJ06.





The resultant On Screen Display circuit now becomes the standard pattern used by many sets. Micro controller RGB out through a voltage divider in into Jungle RGB inputs.



Now that we've got the standard circuit in place we want to implement the RGB Mixing. This is the method pioneered by Syntax and myself to avoid the dreaded OSD snip methods that had been previously used. In this method we mix the external RGB we input with the On Screen Display. Whilst the On Screen Display isn't perfect in RGB mode it is usable and saves a lot of wiring and flicking of switches. On TVs like this one with through hole resistors it is WAY easier to implement than OSD snip, just needs a little maths.

Here is the diagram that serves as template for the OSD/RGB Mix. This is from the test set Syntax first tested the method on..



The spreadsheet used to calculate resistor values is here

Another piece of background knowledge required is that the External RGB video signals must be 75 Ohm terminated. Turns out the mathematics works out so that the existing resistors were suitable and we could implement the external RGB input like this.



In video 1 you will see David making his "little triangles" out of the existing resistors and 75 ohm resistors and then connecting his RGB wires there.

Ok, let's discuss blanking....

My original circuit design, which turns out worked but was flawed was this.



We grab 5V from the unused CN901 port and connect it to the leg of resistor R919. This means the TV's inbuilt voltage divider will reduce the 5V to the 1.5V or so used to induce RGB blanking. Fortunately David implemented this slightly differently at first and instead of soldering the 5V line to the resistor, he soldered to the chip leg of the jungle. This is identical in function but it triggered numerous viewers to note a flaw with this method that was potentially dangerous. He discusses this in the second video and David came up with a solution of instead running the Micro controller's blanking signal and our 5V to the opposite sides of the switch. This enables us to prevent 5V going to the micom and also allows OSD to continue to work in RGB and not RGB modes.



The output of the switch goes to the lifted leg of R919, the leg closest to micro controller. The micro controller's blanking signal comes from the hole left by the lifted leg.

I really like this solution and will be copying it myself.

I'm very glad David implemented it the way he did in the first place otherwise it may not have been so obvious to the viewers that was an issue. Thanks to those who commented/emailed.

That's the thrust of the mod, some other quick things...

A lot of commentators talked about the AV port being Scart shaped. This TV does not have an empty header for RGB scart, it only has the pins for composite video and mono audio.



CN901 is a port used to adjust values in the EEPROM. A lot of sets have these ports and are a great place to find 5V and Ground.

Users also suggested a diode could be inserted on the blanking line from the micro controller, before R919 and then connect the constant 5V to R919. I have taken the time to review the maths on this. It appears it WOULD be suitable to place a 1n4148 switching diode on the line. The 0.7 Volt drop caused by the diode would change the blanking voltage the jungle receives from the micro controller but it would still be within the required range to trigger RGB insertion. By my maths it would end up (5.0 - 0.7) * 4700 / (8200 + 4700) = 1.57 Volts.

[MarkOZLAD]

On the topic of the Closed Captioning Circuit and it's effect on the OSD voltages.

Here is a simulation of the factory circuit.

http://tinyurl.com/ycv6s6fp

Interestigly with the CCD disabled the voltage is 1.7V from the OSD. With it enabled it is 0.7V, seemingly exactly the same as the scart standard. The CCD pulse would dim the RGB signal.

Disabling via jumper has the following result.

http://tinyurl.com/y7bswnbr

[buttersoft]

Smooth moves, as always

[FinalBaton]

Ha! so you're the chap who helped the 8-Bit Guy with his mod I had a feeling it was you. nice

[MarkOZLAD]

There was one other question that kept coming up as to why you would want to do this.

For me it was to find an inexpensive source of Arcade monitors.

Thanks to buttersoft I found out about it.

Massive props, as always, to Syntax too. One talented dude.

[Syntax]

Massive props, as always, to Syntax too. One talented dude.

Aww shucks
You deserve all credit dude after the amount of time you've spent helping random people with RGB mods.

I just wish my camera skills were on par, it stops me from being able to share some of the cool stuff I've built.

[Jaek_3]

I happened to have the exact same CRT and the means so I decided to try out the mod myself and everything works perfectly fine minus the colors, which as you can see are quite faded when cone of my other RGB capable TVs: https://imgur.com/JjzvIT2

EDIT: I've spoken to David and he told me that he had been advised that the resistor values on the RGB line might need adjusting, so I was thinking that I might mount three 1k potentiometers somewhere on my modded case in lieu of the resistors which would also provide me the added advantage of being to manually control the colors, like you can on a high quality broadcast monitor. Do you guys think there's any prospect of this working?

[KatKya]

I had previously asked for a bit of assistance in modding a similar vintage Samsung set which has the same Jungle IC and seemingly much of the same routing as this set. If I were to supply the schematics and such, would it be possible for someone to give advice as to how to do the same mod to my set?

It is a GXE1395, or more commonly the Samsung GXTV, on the KG1 chassis.

Schematic is in this zip: https://files.catbox.moe/bmtmfs.zip

[Syntax]

I had previously asked for a bit of assistance in modding a similar vintage Samsung set which has the same Jungle IC and seemingly much of the same routing as this set. If I were to supply the schematics and such, would it be possible for someone to give advice as to how to do the same mod to my set?

It is a GXE1395, or more commonly the Samsung GXTV, on the KG1 chassis.

Schematic is in this zip: https://files.catbox.moe/bmtmfs.zip

You were just walked through "HOW TO RGB MOD A TV" and your asking someone else to do the brainwork for you now?

The whole purpose of this thread is to make it dead simple for anyone to understand how to mod these.

If your having trouble theres plenty of people here ready to help but have a go yourself first.

[playandpay]

I also have a similar Samsung Tv model TXE-1370 and I am still having a hard time finding the owners manual and/or service manual for the schematics. I am new to this but I am eager to follow through with the RGB mod as I do have a good understanding of electronics.

Feel free to share any information to further build on this forum. Thanks

[KatKya]

No, I can already work out what needs to be done for just the basic RGB mod portion of it; That I am perfectly capable of doing on my own. The thing I'm asking for advice on is in regards to if the set in question has a similar Closed Captioning dimming circuit as the one in 8-Bit Guy's set. If that were not there or at least not mentioned, what is/was already said and shown would be enough to work things out. Additionally, the formatting of the service manual for my set doesn't seamlessly flow between pages as the one in the OP (rather deciding to connect the pages using labeled "bars") works against my already somewhat poor ability to work out a circuit diagram.

I'll also fully admit I missed the spreadsheet until giving the OP a second look through.

Spoiler because wiiiiide image.

Spoiler

Would the edits made to this be the proper bits required for patching in an external RGB source? The RGB lines being the external input, the orange being 75ohm to Ground for termination, the pink being a jumper, and the purple being the fixed blanking switch.

[MarkOZLAD]

Been sick for a week so haven't been able to be of much assistance. I'll get back to answering questions for people as soon as possible.

[MarkOZLAD]

No, I can already work out what needs to be done for just the basic RGB mod portion of it; That I am perfectly capable of doing on my own. The thing I'm asking for advice on is in regards to if the set in question has a similar Closed Captioning dimming circuit as the one in 8-Bit Guy's set. If that were not there or at least not mentioned, what is/was already said and shown would be enough to work things out. Additionally, the formatting of the service manual for my set doesn't seamlessly flow between pages as the one in the OP (rather deciding to connect the pages using labeled "bars") works against my already somewhat poor ability to work out a circuit diagram.

I'll also fully admit I missed the spreadsheet until giving the OP a second look through.

Spoiler because wiiiiide image.

Spoiler

Would the edits made to this be the proper bits required for patching in an external RGB source? The RGB lines being the external input, the orange being 75ohm to Ground for termination, the pink being a jumper, and the purple being the fixed blanking switch.

The diagram you have made looks wrong. If you are to do this the same way as the 8-Bit Guy you would need to lift the legs (farthest from the micom) of OSD grounding resistors R944,, R945 and R946 and tie your 75R to them and inject your RGB between the exiting resistors and 75Rs. These are the "triangles" David refers to. The free leg of the 75R gets soldered into the holes we lifted the legs out of. It's a very quick and dirty method I came up with that works fine.

If the schematic is correct the factory resistor values in the set should be fine for the On Sceen Display. A simple pass at the maths shows the On Screen Display should come out very close to the 0.7V, 5V * (560+75) / (560+75+3900)

Your set does have the same CCD set up as Davids. If it were my set I'd even be tempted to remove that transistor KSR1010. The jumpering shown in your diagram is the same as we implemented for the episodes and will be necessary even if you removed the transistor.

These multi-page schematics are indeed frustrating, part of the reason you see my handwritten notes on here instead of the schematics.

[MarkOZLAD]

I happened to have the exact same CRT and the means so I decided to try out the mod myself and everything works perfectly fine minus the colors, which as you can see are quite faded when cone of my other RGB capable TVs: https://imgur.com/JjzvIT2

EDIT: I've spoken to David and he told me that he had been advised that the resistor values on the RGB line might need adjusting, so I was thinking that I might mount three 1k potentiometers somewhere on my modded case in lieu of the resistors which would also provide me the added advantage of being to manually control the colors, like you can on a high quality broadcast monitor. Do you guys think there's any prospect of this working?

We could try and rework all of the resistor values to lower values if you'd like? I know Syntax has a set of "Go to" values we could try. This would mean replacing the OSD inline and OSD termination resistors with lower values.

[Jaek_3]

We could try and rework all of the resistor values to lower values if you'd like? I know Syntax has a set of "Go to" values we could try. This would mean replacing the OSD inline and OSD termination resistors with lower values.

That sounds great! I'm not exactly an expert in this kind of electronics so I have some potentiometers coming in tomorrow to try manually adjusting the color lines - maybe I can use a multimeter to read out the values that work best... if that would even work. I don't know how to really calculate resistor values myself so this was how I was planning on getting it done.

[MarkOZLAD]

We could try and rework all of the resistor values to lower values if you'd like? I know Syntax has a set of "Go to" values we could try. This would mean replacing the OSD inline and OSD termination resistors with lower values.

That sounds great! I'm not exactly an expert in this kind of electronics so I have some potentiometers coming in tomorrow to try manually adjusting the color lines - maybe I can use a multimeter to read out the values that work best... if that would even work. I don't know how to really calculate resistor values myself so this was how I was planning on getting it done.

Let's try replacing each of R916,R917,R918 OSD inline resistors with 1000 Ohm resistors and replace each of R204,R205 and R206 OSD grounding resistors with 91 Ohm. This is one of the lowest resistance configurations I can come up with. 100 Ohm resistors in place of the 91 Ohms would likely be ok too. The 75 Ohm resistors are still needed as per original spec.

[MarkOZLAD]

I also have a similar Samsung Tv model TXE-1370 and I am still having a hard time finding the owners manual and/or service manual for the schematics. I am new to this but I am eager to follow through with the RGB mod as I do have a good understanding of electronics.

Feel free to share any information to further build on this forum. Thanks

You may have to open up the set and manually inspect the chips to help work out what chassis is in your set. I often find cleaning the chips (with compressed air/isopropyl alcohol) and then photographing the major chips with flash on.

If you can't find a schematic you may need to find individual datasheets to identify the RGB and blanking lines between micro controller and jungle and then reverse engineer your own schematic via photography and/or inspection with a multi-meter.

[Jaek_3]

Done. I opted for 100 ohm resistors in place of 91 ohm ones due to availability and there's definitely an improvement in the overall color fidelity of the image, however it's still rather washed out and in place of the old blue tinge there seems to be a greenish one now. It's worth pointing out that even the composite has an obnoxious blueness to the image that can't be eliminated entirely even after playing around with the menu settings. Also do you think it's possible to integrate a way to manually adjust the colors on the set like you can on most broadcast monitors?

[Syntax]

Looks like to much voltage to blanking causing halftone menu.

Try to lower it with a pot setup as a voltage divider.

[KatKya]

The diagram you have made looks wrong. If you are to do this the same way as the 8-Bit Guy you would need to lift the legs (farthest from the micom) of OSD grounding resistors R944,, R945 and R946 and tie your 75R to them and inject your RGB between the exiting resistors and 75Rs. These are the "triangles" David refers to. The free leg of the 75R gets soldered into the holes we lifted the legs out of. It's a very quick and dirty method I came up with that works fine.

If the schematic is correct the factory resistor values in the set should be fine for the On Sceen Display. A simple pass at the maths shows the On Screen Display should come out very close to the 0.7V, 5V * (560+75) / (560+75+3900)

Your set does have the same CCD set up as Davids. If it were my set I'd even be tempted to remove that transistor KSR1010. The jumpering shown in your diagram is the same as we implemented for the episodes and will be necessary even if you removed the transistor.

These multi-page schematics are indeed frustrating, part of the reason you see my handwritten notes on here instead of the schematics.

I meant to remove the connection to ground in the little sketch up, but forgot to do so before posting. You suggest removing the transistor, why is that? Simply not necessary at that point, or?

I actually went ahead and did the mod work after posting that. Aside from the fact that it seems that the RGB signal seems completely unaffected by the brightness/contrast/etc controls in the basic menu (curious if David's does the same) the image looks pretty fantastic. I'm wondering if adjusting via the service menu might work, but at least for now, it's unnecessary.

https://www.youtube.com/watch?v=u9yI11NkVIs

[MarkOZLAD]

Glad it is working.

I believe that transistor is completely redundant.

If you look at the internal diagram of the jungle chip you’ll see the RGB signal bypasses all the brightness and contrast controls. Just goes into the RGB cutoff stage and back out again.

[KatKya]

I hadn't given it a look, but expected something along those lines. Adjusting G2 was enough to get the brightness correct, and the contrast is perfectly fine; Just means if I decide to use composite for something, I'll have to compensate there instead.

Either way, thank you for distilling some of the more technical bits of this sort of thing into something easier to work out/understand.

[Jaek_3]

Looks like to much voltage to blanking causing halftone menu.

Try to lower it with a pot setup as a voltage divider.

So just hook up a potentiometer to the 5v line on the toggle switch? Wouldn’t that cause the RGB to shut off and switch back to regular composite mode the second the current drops below 5v?

[Jaek_3]

Alright so after fiddling around a bit, I think the fundamental problem is related to the brightness. I had previously lowered the brightness on the flyblack transformer to compensate but obviously this solution wasn't ideal. After putting it back up and installing the new resistors I can see that the colors are more or less what they should be, only extremely washed out and faded. Do you guys idea how to fix this? fix this?

[Syntax]

Looks like to much voltage to blanking causing halftone menu.

Try to lower it with a pot setup as a voltage divider.

So just hook up a potentiometer to the 5v line on the toggle switch? Wouldn’t that cause the RGB to shut off and switch back to regular composite mode the second the current drops below 5v?

Go back and read the blanking data for your chip.
You are misunderstanding its function.
No blanking chip out there requires 5v.
Some have multiple functions across different voltages.
And voltage and current are 2 different things.

[Jaek_3]

Go back and read the blanking data for your chip.
You are misunderstanding its function.
No blanking chip out there requires 5v.
Some have multiple functions across different voltages.
And voltage and current are 2 different things.

Didn't work, unfortunately I think my blanking line is either on or off. Anyways I'm at a bit of a loss as to what to do to get this thing up and running as best I can, are RGB modded consumer CRTs usually this troublesome

[MarkOZLAD]

The block diagram of the TA1201AN showing that the RGB insertion bypasses all the brightness/contrast/sharpness etc. Only the cutoff/drive settings seem to be in play.



With regards to the blanking, the TA1201AN datasheet says that blanking should begin at about 0.7V. There is no mention of half tone in the datasheet that I have found.

Can RGB modding a consumer TV be difficult? Yes! If you're looking for an easy ride this is not the place. Knowledge and success are often hard won. I've personally had many disappointments.

I don't know what is wrong with your set Jaek_3, If I did I would tell you. All I can suggest is that you recheck all your connections with a multi meter. Check that all RGB lines register identical readings along the lines and to ground. Yours certainly would not be the first time I've heard stories of two people modding seemingly identical sets with differing results.

[666sbm]

wow great post

yesterday i posted a question in the big rgb mod thread about modding the same chasis!

so im trying this later!

super thank you

[pyr8]

No, I can already work out what needs to be done for just the basic RGB mod portion of it; That I am perfectly capable of doing on my own. The thing I'm asking for advice on is in regards to if the set in question has a similar Closed Captioning dimming circuit as the one in 8-Bit Guy's set. If that were not there or at least not mentioned, what is/was already said and shown would be enough to work things out. Additionally, the formatting of the service manual for my set doesn't seamlessly flow between pages as the one in the OP (rather deciding to connect the pages using labeled "bars") works against my already somewhat poor ability to work out a circuit diagram.

I'll also fully admit I missed the spreadsheet until giving the OP a second look through.

Spoiler because wiiiiide image.

Spoiler

Would the edits made to this be the proper bits required for patching in an external RGB source? The RGB lines being the external input, the orange being 75ohm to Ground for termination, the pink being a jumper, and the purple being the fixed blanking switch.

The diagram you have made looks wrong. If you are to do this the same way as the 8-Bit Guy you would need to lift the legs (farthest from the micom) of OSD grounding resistors R944,, R945 and R946 and tie your 75R to them and inject your RGB between the exiting resistors and 75Rs. These are the "triangles" David refers to. The free leg of the 75R gets soldered into the holes we lifted the legs out of. It's a very quick and dirty method I came up with that works fine.

If the schematic is correct the factory resistor values in the set should be fine for the On Sceen Display. A simple pass at the maths shows the On Screen Display should come out very close to the 0.7V, 5V * (560+75) / (560+75+3900)

Your set does have the same CCD set up as Davids. If it were my set I'd even be tempted to remove that transistor KSR1010. The jumpering shown in your diagram is the same as we implemented for the episodes and will be necessary even if you removed the transistor.

These multi-page schematics are indeed frustrating, part of the reason you see my handwritten notes on here instead of the schematics.

Hey Mark,

I did the mod as per this thread on the same monitor that KatKya has and the OSD display is totally washed out (bright as hell) now and barely readable. I am wondering if it was the "jumper" mod on 948? "470 Ohm" that caused this? I am thinking I may remove the jumper and see if it fixes the issue. Thoughts?!?!

[undone.evil]

hello i was looking at the wiring diagram from the 8 Bit Guys television and noticed that the resistors on the RGB lines appear to be 3.9K and on your diagram you have 5.4K. im modding my tv for RGB and was just wondering if this is a mistake or if im missing something. thank you