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 Post subject: Re: TV RGB mod thread
PostPosted: Sun Mar 29, 2020 3:56 am 



Joined: 29 Mar 2020
Posts: 6
Hey guys, new guy here i came from the boyac forums looking for help. I got one small 13 inch tv Zanyo, with jungle chip LA7674 and tuning control LSC420142. I think i understand the most , but i just wanted to post here just to make sure i dont screw up. So my question is, based on the schematic, i should solder my rgb cables on jungle 15,16,17 or 18,19,20? i know the 5v i should solder them to -Y in 21, right? And since this particular tv does not have those rca video entrances, should i get the vsync from the tuning chip at 25,24? thanks for any help.
Image Image


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 Post subject: Re: TV RGB mod thread
PostPosted: Sun Mar 29, 2020 11:50 am 



Joined: 16 Mar 2020
Posts: 11
laikmike wrote:
obr wrote:
Here:
https://imgur.com/vclr9UN
You need to cut those lines, also you will need put here also some caps and terminate this input to ground with 75 ohm

Should be good, but you will lose all OSD and TV features


Theres no way i can get OSD with rgb?
about the others tv features i dont mind about it, also which cap do I have to use?

thanks for your replys BTW :D :D :D :D :D


Im not a TV guru, but looks like u cant leave OSD because of this IC(But i can be wrong)
100nF (104) should be good


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 Post subject: Re: TV RGB mod thread
PostPosted: Mon Mar 30, 2020 1:02 am 


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Hey the game sack video used the mux! And BNCs to boot! No switch garbage and no heinous SCART plug


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 Post subject: Re: TV RGB mod thread
PostPosted: Mon Mar 30, 2020 3:53 am 



Joined: 18 May 2017
Posts: 689
laikmike wrote:
obr wrote:
laikmike wrote:
Hello everyone!, hope you can help me with my TV, I want to make the RGB MOD, but i was checking the diagram of my TV (Panasonic CT-F2128S) in the IC601 chip does not have RGB IN just RGB OUT and I dont know if i can perform the mod on this TV also i think is converting RGB to YUV but Idk...
Hope you can help me
i will add a photo
edit: I dont know if the IC601 is the jungle chip
Image

edit2: here are the diagramshttps://diagramas.diagramasde.com/otros2/panasonic_tc-21gx30x_ct-f2128s_ct-g1460mg_ct-f2121g_chassis_gl1.pdf

I guess(not sure) that jungle and controller are combined in this IC. You can try to connect RGB lines directly to tube (before amps ofcourse)


Directly to tube is to the pcb behind the tube?


This jungle doesn't have any RGB inputs, only outputs.
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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: TV RGB mod thread
PostPosted: Mon Mar 30, 2020 3:59 am 



Joined: 18 May 2017
Posts: 689
abispac wrote:
Hey guys, new guy here i came from the boyac forums looking for help. I got one small 13 inch tv Zanyo, with jungle chip LA7674 and tuning control LSC420142. I think i understand the most , but i just wanted to post here just to make sure i dont screw up. So my question is, based on the schematic, i should solder my rgb cables on jungle 15,16,17 or 18,19,20? i know the 5v i should solder them to -Y in 21, right? And since this particular tv does not have those rca video entrances, should i get the vsync from the tuning chip at 25,24? thanks for any help.
Image Image



I can't be sure because I've never encountered this jungle but it looks like it is designed mainly for OSD purposes only. The Blue in is also the blanking signal. I don't think it will be moddable (via Jungle GB injection) but happy to be proven wrong. 15, 16 and 17 are the inputs.
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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: TV RGB mod thread
PostPosted: Mon Mar 30, 2020 5:29 am 



Joined: 31 Jan 2020
Posts: 10
MarkOZLAD wrote:
This jungle doesn't have any RGB inputs, only outputs.


So this jungle chip CANT take RGB MOD? :cry: :cry: :cry: :cry: :cry:


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 Post subject: Re: TV RGB mod thread
PostPosted: Mon Mar 30, 2020 9:08 am 



Joined: 08 May 2018
Posts: 81
Location: Denmark
MarkOZLAD wrote:
abispac wrote:
Hey guys, new guy here i came from the boyac forums looking for help. I got one small 13 inch tv Zanyo, with jungle chip LA7674 and tuning control LSC420142. I think i understand the most , but i just wanted to post here just to make sure i dont screw up. So my question is, based on the schematic, i should solder my rgb cables on jungle 15,16,17 or 18,19,20? i know the 5v i should solder them to -Y in 21, right? And since this particular tv does not have those rca video entrances, should i get the vsync from the tuning chip at 25,24? thanks for any help.
Image Image



I can't be sure because I've never encountered this jungle but it looks like it is designed mainly for OSD purposes only. The Blue in is also the blanking signal. I don't think it will be moddable (via Jungle GB injection) but happy to be proven wrong. 15, 16 and 17 are the inputs.


I would think it to be possible when reading the datasheet, but it seems to need some looking into, because the way its written on how it works looks a bit confusing to me... If I am not completely off, B should be offset 1.5V for the blanking to occur...
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 Post subject: Re: TV RGB mod thread
PostPosted: Mon Mar 30, 2020 9:10 am 



Joined: 08 May 2018
Posts: 81
Location: Denmark
laikmike wrote:
MarkOZLAD wrote:
This jungle doesn't have any RGB inputs, only outputs.


So this jungle chip CANT take RGB MOD? :cry: :cry: :cry: :cry: :cry:


Unless you figure out if the YUV inputs can be changed to RGB instead (by I2C communication) by finding the datasheet or something, then seemingly no. You can of course install an internal RGB->YUV transcoder...
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 Post subject: Re: TV RGB mod thread
PostPosted: Wed Apr 01, 2020 1:04 am 


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Posts: 55
maxtherabbit wrote:
Hey the game sack video used the mux! And BNCs to boot! No switch garbage and no heinous SCART plug


Hey that was me. I actually don't mind doing SCARTS. Joe wanted BNCs because he's setup to route his audio through a sound system and wanted to have BNCs. The customer is always right!


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 Post subject: Re: TV RGB mod thread
PostPosted: Wed Apr 01, 2020 1:31 am 


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Posts: 1179
suprcrackers wrote:
maxtherabbit wrote:
Hey the game sack video used the mux! And BNCs to boot! No switch garbage and no heinous SCART plug


Hey that was me. I actually don't mind doing SCARTS. Joe wanted BNCs because he's setup to route his audio through a sound system and wanted to have BNCs. The customer is always right!

Nice job. My only critique would be to say the RGB wires were excessively long.

I hate SCART hard, but BNC, RCA or VGA are all cool


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 Post subject: Re: TV RGB mod thread
PostPosted: Wed Apr 01, 2020 2:01 am 


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Joined: 15 Apr 2016
Posts: 55
maxtherabbit wrote:
suprcrackers wrote:
maxtherabbit wrote:
Hey the game sack video used the mux! And BNCs to boot! No switch garbage and no heinous SCART plug


Hey that was me. I actually don't mind doing SCARTS. Joe wanted BNCs because he's setup to route his audio through a sound system and wanted to have BNCs. The customer is always right!

Nice job. My only critique would be to say the RGB wires were excessively long.

I hate SCART hard, but BNC, RCA or VGA are all cool


The cable was that way because of the BNC panel mount connectors I had on hand. They were orientated in a way where they had to be mounted in the front and locked into place with a nut in the back. So that means I had to mount the connectors to the back of the set, then solder on the wires. Unlike say a scart where I could just cut the hole and the screw locations, push the scart which is already soldered through the hole from the back side and screw it in from the front. All of this could have been helped if I had some connectors on me which would have allowed me to just rejoin the cable together once I had the BNCs mounted, but this was a last second kind of deal. I live in a part of South Dakota which is about 10 hours away from Denver. I was there because my son gets treatment for his liver disease every six months at Colorado Children's hospital. I forgot my connectors at home along with my step bit of all things. Luckily Joe has some drill bits which worked in a pinch.

I don't know if you get what I'm saying, but normally my RGB wires are shorter. Luckily there was no interference which I was happy about. Also I don't mind SCART. It's nice for the end user just for the economics of using it. There is an abundance of cheap SCART cables for all the major consoles. It can look heinous having a big SCART plug on the back of the set if you don't cut the hole well though. In the end whatever the customer wants is what they get from me. I just wish my new switches had arrived in time. Corona extended the delivery by a couple months so I had to rely on the cheap toggle switch. Oh well.


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 Post subject: Re: TV RGB mod thread
PostPosted: Wed Apr 01, 2020 6:01 am 



Joined: 07 Apr 2016
Posts: 1348
Are there any Consumer CRT TV RGB modders in Ohio? I'm interested in getting one of mine modded.


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 Post subject: Re: TV RGB mod thread
PostPosted: Wed Apr 01, 2020 6:24 am 



Joined: 02 Nov 2013
Posts: 26
I have a Sharp 27C241 I'm hoping to mod.

According to the service manual, it has a IX3354CE jungle chip, which is identical to the LA76843N according to MarkOZLAD.

The RGB and blanking lines each have a 6.8k 1/8W resistor next to IX3528CE (OSD chip). The blanking line also has a 0 ohm resistor next to jungle chip. None of the lines have any capacitors that I can see on any of the diagrams.

I haven't opened it up yet-- I'm hoping to formulate a plan and purchase parts before doing that. Could the PCB have capacitors despite what the service manual shows? Should I wire the RGB lines directly to the chip if there are no capacitors?


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 Post subject: RGB Mod Sharp 27K-S100 running Naomi Jamma I/O 15KHz
PostPosted: Fri Apr 03, 2020 2:54 am 



Joined: 03 Apr 2020
Posts: 2
Image

Image

Image

viewtopic.php?f=6&t=56155&p=1404382&hilit=sharp#p1404382

The thread above was someone modding a 25" model. Things look similar. I never heard if he had success but can anyone help me make sure these steps are correct?

For background/application I am trying to use this in my Naomi cab. If for some reason I can't use the jamma output could I mod a vga cable? In standard res mode?


Last edited by Antler693 on Sat Apr 04, 2020 11:43 pm, edited 1 time in total.

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 Post subject: Re: TV RGB mod thread
PostPosted: Fri Apr 03, 2020 6:01 pm 



Joined: 03 Apr 2020
Posts: 4
Hi All.
I have just done a mod on a NEC FS68v80.
I thought that I did OK but I ended up with a black and white picture and no sound.

The Jungle chip is a TB1227BN. Data sheet found here. https://datasheetspdf.com/pdf/496876/TOSHIBA/TB1227BN/1

According to the data sheet it needs .5v on pin 22 to turn on RGB. (i'm guessing it's an unused teletext mode).

I created a voltage divider with a 75ohm and 10ohm resistor between 5v and Ground. I then wired from between the resistors to one side of a double throw switch (should be around 0.58V).
I then pulled one arm of the resistor connected to pin 22 and connected it to the other side of the switch, hopefully retaining the original circuit. I then ran the middle wire of the switch to pin 22 (I put it in the hole that I pulled the resistor arm from). But no matter what side I have the switch on, I seem to get a sharp but black and white image. When I middle the switch so nothing is connected to 22, I get colour, but it seems there is no green and the image isn't as sharp (probably composite video).

There were already 3 caps connected to the rgb inputs of the jungle chip (23, 24, 25), they are 103J caps. I then traced back on the PCB to the absent TEXT circuit where there was a wire link for each of the caps tying the negative side of the caps to ground. I removed these links and replaced them with a 75ohm resistor for each colour, therefor terminating them to ground. I connected the RGB wires from my Scart Connector (pins 15, 11, 7) to the leg of the resistor not tied to ground (connected to the negative leg of the caps). I also pulled ground off of one of the resistors for the scart plug and ran it to pins 4, 18 and 21.

For Sync I used a double throw switch so that I could switch between S-Video Luma and Composite Video, and wired the middle leg of the switch to pin 20 of the scart plug. When on composite video I get a very sharp but black and white image, on S-video Luma I just get a jumbled mess.

For the audio I tried connecting to the Stereo Jacks on Input 1, then to pins 2 and 6 respectively on the scart plug, but all I get is a quiet buzz and no Audio. Looking at the service manual It looks as though there is some sort of internal switch or something that the plug will open when inserted. All of the jacks seem to be shorted together when testing with a continuity meter.

I tried using the S-Video connection with RCA stereo and everything seems to work fine that way, but there is still some audio buzz when there is no signal.

TV tested with a PAL SNES using RGB Sync on Luma cable from retro gaming cables. and S-Video. I can test with a NTSC SNES, Mega Drive or Modded PAL N64 if need be.

Hopefully someone can help me.

Cheers and thanks for your time.


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 Post subject: Re: TV RGB mod thread
PostPosted: Sat Apr 04, 2020 5:23 pm 



Joined: 03 Apr 2020
Posts: 4
I'm not sure if this'll come out in order, as I haven't seen my original post go up yet.

Anyway...

I seem to have had success with the NEC FS68v80. After reading a few of the posts, and watching a couple of video's on youtube. I saw how important it seems to ground all 'ground' pins on the scart plug.

I also got inspired by MarkOZLAD's external MUX and ran s-video and audio from the AV1 sockets into the Sync pins and audio pins respectively on the scart plug. This solved both the no audio and Luma sync issues I was having before.

Now the thing I can't explain. According to the Toshiba TB1227BN data sheet, pin 22 needs 0.5v to activate RGB mode. So as I stated in the past post I used a 2 throw switch to change from ground to 0.5v.
Both of these options are giving me a black and white image. But when I middle the switch (effectively putting nothing on pin 22) I get RGB displayed. I tested this by removing the blue wire from the scart plug, and found that I was indeed getting RGB since blue was now missing. I have no idea why this is happening, But I'm not going to question it. It's working.
I'm also getting all the OSD, which is a real plus.

Would anyone here have any idea why it seems to be working this way?

I tested it using the following consoles, and all worked fine.
SNES (Pal and NTSC), NES with RGB mod, N64 with RGB mod, Mega Drive, Game Cube, PS2
It looks nice and clear, but it's slightly less vivid than my LG Flatron running component via a SB RGB to Ypbpr convertor for the 480i consoles.

Pics
Image
Image
Image
Image
Switch UP 0v on pin 22 (original circuit)
https://imgur.com/D0lxeYt
Switch Down 0.58v on pin 22 (voltage not actually read, only calculated)
https://imgur.com/hYmoVBN
Switch Middle Nothing on pin 22
https://imgur.com/1jijUho


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 Post subject: Re: TV RGB mod thread
PostPosted: Sat Apr 04, 2020 5:46 pm 



Joined: 29 Mar 2020
Posts: 6
I'm trying my hand at modding a Panasonic CT20G6DE I just got for this purpose. Unfortunately it has an integrated single chip setup instead of the seperate jungle IC I was expecting, so most of the info I have found doesn't seem to apply. Is it still possible to RGB mod this TV? I have been looking at the service manual and I don't see where I could inject the RGB signal. If anyone is willing to take a look and help me out it would be greatly appreciated. :)

Here is a link the a PDF of the circuit diagram: https://drive.google.com/open?id=14WpQZ ... T8SMEoYIIY
sorry about the rotation

and here is a link with the service manual: https://drive.google.com/open?id=1KzhM9 ... gVkOV1QeEo
pages 48-49

Thanks for anyone feeling generous enough with their time to take a look at this!

edit: https://www.digchip.com/datasheets/down ... =M65580MAP
here is the datasheet for the main IC

(http://mikejmoffitt.com/img/tv_rgb_injection.png)
What I tried to do is connect the RGB lines to the OSD in RGB pins(51,49,48) which seem to be connected to the nearby 55,57,58 which are labelled simply r,g, and b. I used this diagram to wire the lines in and I was planning to leave the composite video cable connected for now in order to provide sync. I did not put the OSD on a switch, I just wanted to see if I could get this working and then possibly add switches for OSD if I felt up to it. I did not cut the traces between the pins on the processor since I'm not sure if I'm on the right track. I did knock off one SMT resistor. I connected 5v on a switch to FAST BLK(pin50) but it doesnt seem to do anything. The OSD is now messed up and unreadable, I never tried it before though. I'm getting signal from the composite in but when I flip the switch to supply 5v to FAST BLK it doesn't seem to do anything. I'm not sure what input/channel I should be on in order to see the RGB picture.

I'm kinda feeling my way in the dark here, trying to learn something new. I do have an oscilliscope and I tried checking the RGB pins and there is some kind of signal there. I'm not sure where to go from here.

I should mention I am hooking it up to an RGB modded SNES mini, since I dont have a SCART cable for it and it's pretty tough to get anything currently I just soldered some thin wires into RGB pins where they leave the SNES and I am running them into the TV, then using the stock composite cable to connect sound and composite for sync.


Last edited by bengmo on Sun Apr 05, 2020 1:09 am, edited 2 times in total.

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 Post subject: Re: TV RGB mod thread
PostPosted: Sat Apr 04, 2020 8:06 pm 



Joined: 04 Apr 2020
Posts: 2
I’m happy to find this thread and appreciate everyone that has contributed information! I’m looking for some assistance and will be happy to provide a donation for someone’s time.

I’m trying to figure out the circuit on my Samsung TXK2554. The service manual is supposed to cover this model along with some variants. The problem is the schematic seems to only reference the variations which include components that my TV doesn’t have like the Picture in Picture chip along with SCART and VGA inputs. For this reason I can’t determine the best approach to tap into the RGB lines or the proper resistor values. I would appreciate it if anyone can take a look at the service manual and see if I’m missing something. Perhaps it does show the how the circuit works without those additional components: https://www.manualslib.com/manual/43513 ... k2554.html

The jingle chip actually has two sets of RGB inputs: one for the OSD and the other for PIP but I’m making the assumption that I can only tap into the OSD lines on the model I own because it is missing the logic to switch to those lines since it has no PIP chip. If anything perhaps I can tap directly into the jungle chip and use separate pots for blanking and the RGB starting with higher resistance pots until I get to the proper voltage to blank and get a picture?

As you can see I’m pretty ignorant on this subject but I’ve been doing my best to grasp things. If only this circuit was similar to the Samsung that the 8 Bit Guy worked on. Thanks to MarkOZLAD and Syntax I understand how that worked along with doing the math to get the resistor values. Any input is greatly appreciated, thanks!


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 Post subject: Re: TV RGB mod thread
PostPosted: Sun Apr 05, 2020 7:43 am 



Joined: 24 Mar 2020
Posts: 2
Could anyone tell me where the blanking pin is on this IC.

https://imgur.com/a/3H2ZAHo

the tv is a 32" sanyo


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 Post subject: Re: TV RGB mod thread
PostPosted: Sun Apr 05, 2020 7:44 am 



Joined: 12 Apr 2018
Posts: 15
I’m in the exact same boat as (at least) two other posters on the thread. The jungle IC I’m looking at has blue and blanking on the same input.

The chip is the same mentioned by abispac above which is a LA7674. It also resembles an earlier post by thedudeabides (page 94) with a LA7672.

https://www.audiolabga.com/pdf/LA7674.pdf

I’m unable to tell if the IC is digital only and how to supply blanking and blue to the same pin (pin17).

The CRT in my case is a is a Mitsubishi CS-27305 and I unfortunately can’t find a service manual for it. Also, I actually picked up this TV, unopened, in the original box so I’d love to get it working rather than finding a different one.

Display Controller is a:M73266ME-A66SP
https://www.alldatasheet.com/datasheet- ... 266ME.html

Anyway, I’d appreciate any help and maybe others would too!


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 Post subject: Re: TV RGB mod thread
PostPosted: Sun Apr 05, 2020 8:48 am 



Joined: 08 May 2018
Posts: 81
Location: Denmark
F-Bomb wrote:
I'm not sure if this'll come out in order, as I haven't seen my original post go up yet.

Anyway...

I seem to have had success with the NEC FS68v80. After reading a few of the posts, and watching a couple of video's on youtube. I saw how important it seems to ground all 'ground' pins on the scart plug.

I also got inspired by MarkOZLAD's external MUX and ran s-video and audio from the AV1 sockets into the Sync pins and audio pins respectively on the scart plug. This solved both the no audio and Luma sync issues I was having before.

Now the thing I can't explain. According to the Toshiba TB1227BN data sheet, pin 22 needs 0.5v to activate RGB mode. So as I stated in the past post I used a 2 throw switch to change from ground to 0.5v.

It's a common misconception that the pins need 0.5V, it needs *at least* 0.5V to switch. However that voltage will vary some, and it could be it works when you're in the middle position and thus the input is floating (which is a bad thing). Instead put a 10K pulldown resistor on it, and then only switch 5V in, so you don't have any undefined states, either it's pulled to GND by the 10K resistor, or you have 5V on it.
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 Post subject: Re: TV RGB mod thread
PostPosted: Sun Apr 05, 2020 8:52 am 



Joined: 08 May 2018
Posts: 81
Location: Denmark
SlightlyObsessed wrote:
I’m in the exact same boat as (at least) two other posters on the thread. The jungle IC I’m looking at has blue and blanking on the same input.

The chip is the same mentioned by abispac above which is a LA7674. It also resembles an earlier post by thedudeabides (page 94) with a LA7672.

https://www.audiolabga.com/pdf/LA7674.pdf

I’m unable to tell if the IC is digital only and how to supply blanking and blue to the same pin (pin17).



It says linear RGB input so pretty sure it's not digital. Also you can simply create a DC offset to your signal to obtain the switch voltage. There are many ways to do this depending on your requirements, with the simplest being a voltage divider with your signal coming in "in the middle" to using an om-amp to sum voltages.
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 Post subject: Re: TV RGB mod thread
PostPosted: Sun Apr 05, 2020 10:06 am 



Joined: 19 Mar 2020
Posts: 4
obr wrote:
Surfovod wrote:
Hello.
I have a TV Panasonic TC-2155R, with a chassis MX-3C http://gaf.kz/tv/AN.PDF, a video processor AN5192K http://gaf.kz/tv/MX.pdf.
I want to connect a 60-in-1 Chinese gaming board for vertical games.
Image

Connected according to the picture. I picked up all the necessary resistances and ceramic capacitors. The colors are very good, bright, they delight me, but there is one problem - the geometry of the picture is broken (the image is shifted). I read the whole topic, I realized that the reason for this is a comb filter. It is recommended to connect directly to the luma S-video, but I do not have such an input, only composite (AB). I tried to connect directly to Y-in (43) and CHROMA-in (48) there is no effect, I even tried to connect to the contacts of vertical and horizontal synchronization (45,46) (the geometry is not straightened). I would configure the geometry through the service menu, but the original remote is lost, I don’t know how to enter the service menu without it.
I am in despair, ready to throw the TV into the abyss.

Please tell me how to get around this comb filter? are there any methods?
Or maybe it is possible to enter the service menu without the original remote?
I would be grateful for any help


Could you please show a picture of wrong geometry?

I corrected the image on Panasonic using the service menu of the TV, I could not tear it apart
Now I have another Sony Trinitron KV-25R1R TV with a BE-5 chassis, I connected the RGB via SCART, it is also shown with an offset (I attach the photo). How to cure it? Tell me please.
Image


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 Post subject: Re: TV RGB mod thread
PostPosted: Sun Apr 05, 2020 10:42 am 



Joined: 12 Apr 2018
Posts: 15
skum wrote:
SlightlyObsessed wrote:
I’m in the exact same boat as (at least) two other posters on the thread. The jungle IC I’m looking at has blue and blanking on the same input.

The chip is the same mentioned by abispac above which is a LA7674. It also resembles an earlier post by thedudeabides (page 94) with a LA7672.

https://www.audiolabga.com/pdf/LA7674.pdf

I’m unable to tell if the IC is digital only and how to supply blanking and blue to the same pin (pin17).



It says linear RGB input so pretty sure it's not digital. Also you can simply create a DC offset to your signal to obtain the switch voltage. There are many ways to do this depending on your requirements, with the simplest being a voltage divider with your signal coming in "in the middle" to using an om-amp to sum voltages.


Thanks skum that gives me hope. Requirements would be to send the standard voltage (with 75ohm termination) on the blue line for video termination including both the blue signal and the required blanking (pulled high I think, using 5v from the board somewhere). I somewhat follow you on how to achieve this but likely need a diagram or reference on how to build that circuit. I can read up more tomorrow, and it’s probably simple but so far I’m not seeing how I’d setup the voltage divider (or an op amp) to achieve a solution. If you have an idea how to build it or can give me more direction let me know and I’ll give it a shot and report back.

Thanks!


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 Post subject: Re: TV RGB mod thread
PostPosted: Sun Apr 05, 2020 11:09 am 



Joined: 03 Apr 2020
Posts: 4
skum wrote:
F-Bomb wrote:
I'm not sure if this'll come out in order, as I haven't seen my original post go up yet.

Anyway...

I seem to have had success with the NEC FS68v80. After reading a few of the posts, and watching a couple of video's on youtube. I saw how important it seems to ground all 'ground' pins on the scart plug.

I also got inspired by MarkOZLAD's external MUX and ran s-video and audio from the AV1 sockets into the Sync pins and audio pins respectively on the scart plug. This solved both the no audio and Luma sync issues I was having before.

Now the thing I can't explain. According to the Toshiba TB1227BN data sheet, pin 22 needs 0.5v to activate RGB mode. So as I stated in the past post I used a 2 throw switch to change from ground to 0.5v.

It's a common misconception that the pins need 0.5V, it needs *at least* 0.5V to switch. However that voltage will vary some, and it could be it works when you're in the middle position and thus the input is floating (which is a bad thing). Instead put a 10K pulldown resistor on it, and then only switch 5V in, so you don't have any undefined states, either it's pulled to GND by the 10K resistor, or you have 5V on it.


This is what I currently have installed.
Image
From what you are saying, should it be more like this?
Image

Or do I just need to change 0.5v to 5v?

You can see the wiring on the third picture of my original post.
The two resistors near the black cable are the voltage divider. I can remove them. Where the 75ohm resistor goes into the board is 5v so I can put the grey wire in there.
The resistor where the black wire is attached is R313 10Kohm. I should be able to put that back into the hole where the Brown wire is.

Let me know if this is correct and I'll make the change and let you know how it goes.


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 Post subject: Re: TV RGB mod thread
PostPosted: Sun Apr 05, 2020 12:13 pm 



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F-Bomb wrote:
Or do I just need to change 0.5v to 5v?

You can see the wiring on the third picture of my original post.
The two resistors near the black cable are the voltage divider. I can remove them. Where the 75ohm resistor goes into the board is 5v so I can put the grey wire in there.
The resistor where the black wire is attached is R313 10Kohm. I should be able to put that back into the hole where the Brown wire is.

Let me know if this is correct and I'll make the change and let you know how it goes.


The original R313 10K is most likely just a current limiter (wise) so inject before that. Is R319 populated? Otherwise that's where I'd put a 10K in (the value is not that important, it's simply to avoid drawing too much current when 5V is injected). So between R313 and R319 (which if not there, add a resistor to the pads) is where your switch should simply inject 5V, basically what your drawing shows. At least that's how I'd try it if I was doing it :) No guarantees made, and smoke and fire is of course to be expected ;)
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 Post subject: Re: TV RGB mod thread
PostPosted: Sun Apr 05, 2020 12:27 pm 



Joined: 08 May 2018
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Location: Denmark
SlightlyObsessed wrote:
skum wrote:
SlightlyObsessed wrote:
I’m in the exact same boat as (at least) two other posters on the thread. The jungle IC I’m looking at has blue and blanking on the same input.

The chip is the same mentioned by abispac above which is a LA7674. It also resembles an earlier post by thedudeabides (page 94) with a LA7672.

https://www.audiolabga.com/pdf/LA7674.pdf

I’m unable to tell if the IC is digital only and how to supply blanking and blue to the same pin (pin17).



It says linear RGB input so pretty sure it's not digital. Also you can simply create a DC offset to your signal to obtain the switch voltage. There are many ways to do this depending on your requirements, with the simplest being a voltage divider with your signal coming in "in the middle" to using an om-amp to sum voltages.


Thanks skum that gives me hope. Requirements would be to send the standard voltage (with 75ohm termination) on the blue line for video termination including both the blue signal and the required blanking (pulled high I think, using 5v from the board somewhere). I somewhat follow you on how to achieve this but likely need a diagram or reference on how to build that circuit. I can read up more tomorrow, and it’s probably simple but so far I’m not seeing how I’d setup the voltage divider (or an op amp) to achieve a solution. If you have an idea how to build it or can give me more direction let me know and I’ll give it a shot and report back.

Thanks!


They actually show an example of the circuit in the datasheet you link to on page 5. You can see they use a simple voltage divider approach, the question is then what voltage to apply at the BLANKING-IN resistor (the 2.7k). Most likely this should be 3V or higher, which will then result (at 3V) with an added voltage of ~1.8V, which I guess should be enough for blanking if the threshold is maximum 1.1V (if I read the datasheet correct).
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 Post subject: Re: TV RGB mod thread
PostPosted: Sun Apr 05, 2020 5:28 pm 



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skum wrote:
They actually show an example of the circuit in the datasheet you link to on page 5. You can see they use a simple voltage divider approach, the question is then what voltage to apply at the BLANKING-IN resistor (the 2.7k). Most likely this should be 3V or higher, which will then result (at 3V) with an added voltage of ~1.8V, which I guess should be enough for blanking if the threshold is maximum 1.1V (if I read the datasheet correct).


Here’s their example you reference:
Image

If I were to try and merge the concepts...would this be it?
Image


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 Post subject: Re: TV RGB mod thread
PostPosted: Sun Apr 05, 2020 5:35 pm 



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SlightlyObsessed wrote:
...huge pictures...


Yeah something like that. But I haven't done any calculations as to how it would play out. I am however unsure if your inputs needs to be offset already, as I really dont know how to read these RGB - Y out DC (3-5V) numbers... Before applying any video, I'd definitely see if I could get it blanking first...
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 Post subject: Re: TV RGB mod thread
PostPosted: Sun Apr 05, 2020 6:08 pm 



Joined: 12 Apr 2018
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skum wrote:
SlightlyObsessed wrote:
...huge pictures...


Yeah something like that. But I haven't done any calculations as to how it would play out. I am however unsure if your inputs needs to be offset already, as I really dont know how to read these RGB - Y out DC (3-5V) numbers... Before applying any video, I'd definitely see if I could get it blanking first...


Lol sorry about the Uuge pics. I fussed with them for quite a while. :x So you think I may need to lower the 5v on the blanking side (hopefully not the blue side)? Maybe a voltage divider in front of the blanking side to bring down the 5v? Is that what you mean? Also, where are you seeing the “RGB - Y out DC (3-5V)” numbers? Thanks for the help, it’s a bit over my current knowledge level! :)


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