RGB Modding of a 2005 Sanyo CRT TV. Is it possible?

[benyamin40]

Hi,

I have bought a 19" CRT TV to fit into my late 80s arcade cabinet. I aim at doing an RGB mod and I want to know if this is doable.

I have some limited knowledge in electronics (although I managed to repair my coffee machine PCB by replacing a dead resistor). I have done a ot of research on the web and it seems I should not have much hope. But I wanted to make sure.

Model is Sanyo ds19204, made in 2005.

I opened the TV (safely), discharge and unmount the PCB. BElow is the picture of the chipset



The big chip (IC101) is Sanyo LA76843M 80 pins. I could not find the datasheet on the web. If anyone has a datasheet that could do, I am interested.
The other chips (IC801) is S031 AVC084 51K9 (I found the datasheet on the web but the chip looks different with many more pins, so not much success here again.)

I am afraid this TV has no OSD chip I can bypass and as I think the OSD is integrated in the 80 pin. But before I seek for another 19" CRT TV I wanted to make sure. If there is any way I can mod this TV, I am willing to give it a go.

Thx for you help.

[skum]

Manualslib seem to have the service manual. According to that IC801 sends OSD RGB out from pin 22 (blanking), 21 (B), 20 (G), 19(R) to IC101 pin 15 (blanking), 14 (B), 13 (G), 12 (R).
Blanking goes through R846 (10K), RGB goes through 6.8K R849, R847, R848 respectively. So it seems a candidate for an OSD mux, unless the RGB are digital, but I wouldn't think so given its internal block that mentions amplification and brightness stuff.

[benyamin39]

Thanks very much for the information. I enlarged the PCB board drawing and marked the RGB and blank lines path. I will try to post a scan of my PCB markup

I followed the "8-Bit Guy" thread, in which it is mentioned about setting up the voltage divider.

So I had to find the resistors connected to ground. I believe they are R842/R843/R844 (interestingly I found the information in the DS19330 chassis service manual as those resistors are not indicated in the DS19204 service manual). Their capacity is 820 ohms.

I used the spreadsheet in the thread and the calculated a resistance of 300ohms to be added.

Now my last difficulty (if everything I mentioned before is correct), is to insert those resistances. I don't know how I can unsolder those tiny ground resistors. I wonder what is the best approach. Appreciate anybody's opinion.


Thx!

[benyamin40]

Thank you!

I managed to trace down on the PCB drawing the RGB and Sync lines and location of the various resistors.

Initially I wanted to follow the "8-bit guy RGB mod" thread for ground resistor sizing but found out that my PCB has no ground resistor, nor capacitor. It is a Straight line OSD -> Resistor -> Jungle chip input.

1. Does that mean I can inject the VGA signal straight at the jungle chip input and forget about the resistor divider scheme presented in the thread?

2. Do I need to add a 75 ohm resistor and 104 caps?

Thx for your help.

[amiqrongdude]

Curious if you got this working?

[benyamin39]

Unfortunately the tv died before i could test it. Trying on another set...

[benyamin39]

Unfortunately the tv died before i could test it. Trying on another set...

Well I manage to resurrect my Sanyo TV and I am trying again to mod it. In the mean time I managed to mod successfully a Samsung TV and blew up an old JVC TV. So I gained a bit of experience.

Here is my proposed mod for the Sanyo. I wish someone can vet it before I proceed as the diagram is a bit different from usually seen (and I don't want to blow up this TV).

The connection from OSD to Jungle chip is straight via a resistor. There is not ground resistor on the PCB (my previous post on R842/843/844 was misleading. They actually do not exist on the board...). That is the specific thing about this TV.

In the picture attached I have marked up what I think could work.

1. Iinject VGA signal via a 1100kohm resistor
2. I add a 75 ohm resistor to the PCB ground. I don't think it can harm.
3. I pick the ground from the PCB and connect to the VGA ground (same as on the Samsung, I guess that is why I blew up the JVC TV, I think I forgot to do that properly).

[matt]

This TV looks suspicious. In my experience, a schematic that look like this (no coupling capacitors or resistors to ground) usually means one of two things: digital RGB or weird input voltage levels. I've had bad luck with some of these Sanyo jungle chips, and without a datasheet it could be anything.

First thing you should do is test the blanking. If you get a white screen, it's probably not going to work. If it's black, you might have a chance.

Your plan looks like a good starting point for injecting RGB (although most of the time there are 0.1uF caps between the RGB signal and the jungle). But, don't be surprised if it doesn't work right away. Put everything on some breadboard at first so you can change components as needed. If you hook it up the way you've illustrated and nothing happens, you may want to remove the inline resistors from the PCB and inject the signal straight to the jungle chip (without the 1100ohm resistors) to see what happens. You may have to change/remove your termination resistors, add or remove coupling capacitors, or maybe even add a video amp - once that's settled you can figure out how to mix the OSD back in.

[benyamin39]

This TV looks suspicious. In my experience, a schematic that look like this (no coupling capacitors or resistors to ground) usually means one of two things: digital RGB or weird input voltage levels. I've had bad luck with some of these Sanyo jungle chips, and without a datasheet it could be anything.

First thing you should do is test the blanking. If you get a white screen, it's probably not going to work. If it's black, you might have a chance.

Your plan looks like a good starting point for injecting RGB (although most of the time there are 0.1uF caps between the RGB signal and the jungle). But, don't be surprised if it doesn't work right away. Put everything on some breadboard at first so you can change components as needed. If you hook it up the way you've illustrated and nothing happens, you may want to remove the inline resistors from the PCB and inject the signal straight to the jungle chip (without the 1100ohm resistors) to see what happens. You may have to change/remove your termination resistors, add or remove coupling capacitors, or maybe even add a video amp - once that's settled you can figure out how to mix the OSD back in.

Hi Matt,
The OSD Chips is an LA76843N (datasheet below). It looks like it is analog, but I am not sure.
I picked a 5V signal from the board for blanking. When I measured I got only 4V, but I guess it should be sufficient.

I tested my configuration and I get a black screen (I confirm the tube is on, because when I switch off the TV, there is quick flash). It is not white, So maybe a good sign? I wonder though why I don't get something (channel number) from the OSD with this configuration. It is a problem coz I can't set any parameter on the TV.

I need to test injecting a signal now.

[MrMcTiller]

Hi, I'm curious to see if you got this working. I am wanting to mod a similar Sanyo TV that has the same chips.

[benyamin39]

Hi, I'm curious to see if you got this working. I am wanting to mod a similar Sanyo TV that has the same chips.

Hi. I am not very successful at the moment. I disconnected my blanking signal bypass. I still have a black picture. So the problem is on the RGB signal. I suspect the PCB does not like the fact that I introduced a resistor voltage divider. I will try to inject directly 0.7V to the jungle chip without 75ohm connected to the ground. If this does not work, I don't know what else to do really.

Also, what I do not know is the expected voltage on the jungle chip considering that there is 5V output from the OSD and a 6800k resistor. Is there a way to calculate what is the anticipated voltage on the jungle chip side?

[benyamin39]

Hi, I'm curious to see if you got this working. I am wanting to mod a similar Sanyo TV that has the same chips.

Hi. I am not very successful at the moment. I disconnected my blanking signal bypass. I still have a black picture. So the problem is on the RGB signal. I suspect the PCB does not like the fact that I introduced a resistor voltage divider. I will try to inject directly 0.7V to the jungle chip without 75ohm connected to the ground. If this does not work, I don't know what else to do really.

Also, what I do not know is the expected voltage on the jungle chip considering that there is 5V output from the OSD and a 6800ohm resistor. Is there a way to calculate what is the anticipated voltage on the jungle chip side?

Here is the follow up. I removed all the modding and only tested the RED signal by injecting 1V straight after the 6.8k resistor, without any 75 ohm to the ground. To do so, I used a simple 1.5V battery (reason is, I already burnt a video card with another TV I tried to mod, so I want to be cautious this time). I left the 1.1k resistor for the moment.

When I inject the RED signal with the TV off, I got 0.96V at my injection point and 0.6mA. I have no idea if this is good or not, but it looks like I can test the TV on with those values.

So I switched on the TV, everything is fine and the upper right of the picture display "VIDEO" characters in green on a blue background.

Then I inject the RED signal and at first nothing change in the picture at all.

Then I test the OSD further by selecting the menu. This time, the picture shows more characters, some of them in bright red (UHF/VHF options, ...)

Then I inject the RED signal again and this time those same red characters become dim red. so my RED signal injection is doing something, but not what I expect.

Since I inject a continuous 1V signal, I would expect the entire screen to turn reddish (or a mix of Red and blue), but this is not happening. Possibly my RED signal was too weak.

So I tested the RED signal again with this time 2x1.5V batteries. This time the entire screen turned pinkish!

I will try next by replacing the 1.1k resistor with a variable resistor and see what happen. I will also test a voltage divider to test 0.7V from my 1.5V battery and go with lower resistor. value.

I need some insights though. What matters to the jungle chip to get the picture right? Purely the correct voltage input? or a correct voltage input and sufficient amp level?

[matt]

Do you still have the blanking switch hooked up? If you're trying to test one of the color channels it's better to do it without activating the OSD.

If this jungle chip will take analog RGB, it may not be in the usual 0.7p-p format. As long as the blanking is functional, you can try feeding the RGB signals straight from your test console to the jungle chip inputs with no terminating resistors or inline capacitors. If you get any results, it may be possible to do the mod but you'll need a video amp.

[benyamin39]

Do you still have the blanking switch hooked up? If you're trying to test one of the color channels it's better to do it without activating the OSD.

If this jungle chip will take analog RGB, it may not be in the usual 0.7p-p format. As long as the blanking is functional, you can try feeding the RGB signals straight from your test console to the jungle chip inputs with no terminating resistors or inline capacitors. If you get any results, it may be possible to do the mod but you'll need a video amp.

I have the blanking switch hooked up and it works well. I input the signal from a TV Box and once I activate the blanking switch the screen turn black. So I am good there.
Then I have tested various input voltage and resistor configuration and the conclusion is that :
1. at 1.4V at the jungle chip I get nothing. at 2.2-2.4V volt I got a perfect red screen (beyond 2.2V there is no difference)
2. no terminating resistors is required.

I think I have been as far as I could and my questions are:

1. Is the jungle chip expecting a 0-2.2V range or 1.2-2.2V range?
2. What would be the easiest voltage amplifier I could use to make this modding work (I spent quite some time on this TV, so after all I don't mind trying one).

[matt]

Does the brightness change between 1.4v and 2.2v? If not then you definitely have a digital-only jungle chip.

The THS video amps seem to be the most popular: https://www.retrorgb.com/thsamps.html

I've never tried it with a TV mod, although it's on my to-do list.

[benyamin39]

Does the brightness change between 1.4v and 2.2v? If not then you definitely have a digital-only jungle chip.

The THS video amps seem to be the most popular: https://www.retrorgb.com/thsamps.html

I've never tried it with a TV mod, although it's on my to-do list.

The brightness change between 1.4V and 2.2V. So I am pretty sure it is analog. I wonder though why 0-1.4V range is flat (absolute dark). maybe there is not a linear relationship between voltage and brightness?

Thx for the link, I have studyied it. I need to figure out out to adjust the amplification level on the chip to what I need.

[benyamin39]

Does the brightness change between 1.4v and 2.2v? If not then you definitely have a digital-only jungle chip.

The THS video amps seem to be the most popular: https://www.retrorgb.com/thsamps.html

I've never tried it with a TV mod, although it's on my to-do list.

The brightness change between 1.4V and 2.2V. So I am pretty sure it is analog. I wonder though why 0-1.4V range is flat (absolute dark). maybe there is not a linear relationship between voltage and brightness?

Thx for the link, I have studyied it. I need to figure out out to adjust the amplification level on the chip to what I need.

Hi
The THS 7314 and 7316 have a 2V/V gain level (6dB). I need about 3.5/4 V/V (12dB) to boost from .7V to about 2.2.
I found other reference :
THS 7315 (5.2V/V)
THS 7320 (4V/V)
THS 7375 (5.6V/V)
I will try my luck with the first 2 units and add couple of resistors to lower the voltage. I think I can get something, but I am not sure of the picture quality I will get. Anyone thought on this is well appreciated as I am not an advanced electronic guy. This is very exploratory.

[matt]

The RGB signals are only 0.7v after 75 ohm termination, if you experiment with different resistors on the input and output side you should be able to get it to the right level.

[matt]

Alternatively, it might be possible to bring up your RGB levels with passive components (diodes and resistors from a +5v source). I don't have enough experience to advise you on the best way to do this, however.

[benyamin39]

Alternatively, it might be possible to bring up your RGB levels with passive components (diodes and resistors from a +5v source). I don't have enough experience to advise you on the best way to do this, however.

Ok, I have received the THS7315 and wired it up. upstream of the THS I put a 75 ohm resistor to the ground for the RGB input but it does not change anything to the picture level. Downstream I put a resistor and connected straight to the junglechip (I also tested a voltage divider but that does not seem to change anything). I prepared a breadboard to test various resistor value.

The good news is I got a picture on the TV.


the bad news is the colors are ugly.

I tested the picture against a calibration image found on the following website https://www.equilter.com/help/calibration


I should see 20 shades of red on the second row (Red). I see only 4 different levels. 9 black , shade, shade, 9 red
I adjusted the resistor from 1800ohm to 10k. the brightness of the red change, but I still get very few shades.





I was afraid of that although I hade some hope since I could modulate the red level from 1.2 to 2.4 volts, but apparently it is more complicated than that. Is it a digital signal that is expected?

Any help is appreciated. I have been as far as I could on this TV and I don't think I am far from a solution.

[benyamin39]

Here below are snapshot of the service manual for the chipsets, if this may help.



There is a voltage chart as well that provide voltage levels for color bar signal. Not sure if this is useful though.



It looks like is an analog signal.

Assuming it is an analog signal, I am tempted to apply further signal transformation to shift the 0-0.7Vpp signal in the 1.4V-2.1V range and see if I get a proper color grading. I red on the web to use a Rail-to Rail I/O opamp. Has anyone tried that before?

[benyamin39]

Continuing with the subject:
I put a 1.5V battery in series with the Red signal to shift the signal by 1.5V



I got more color grading now. About 8 to 10 shades on the red. So halfway to success. Still there are black area on the left and saturation on the right. A range 1.7 / 2.2V would probably bring me to the color grading comparable to the calibration picture.

To double check this weird voltage range I tried again to apply a simple constant voltage on the Red signal using again 2x1.5V batteries and a voltage divider. I retained the green and blue signal from the computer. What I got is hard to explain.
Here is the picture with only green and blue signal coming from the computer web browser


Here is the picture after applying a 2.76V on the red signal. Other colors are affected! This should not be the case for an RGB signal. Black becomes redish tinted black. But more curiously, some bright Red bars appear wherever there were blue signal (basically the 4 bottom bars of the calibration picture). I wonder whether it is an YPrPb signal? Or maybe I saturated one of the chips. Hope someone can make sense of it and give me the key to success. In the mean time I am thinking about getting a summing op amp and put in place a voltage divider to shift the signal to 1.7V/2.2v.

[Pwnisher]

Hello folks. I have been trying my hand at my first rgb mod with a 9" Memorex dvd combo. I haven't been able to find documentation for this set's jungle, but I think it may be of Sanyo lineage. I would love to hear about progress on this mod you've made. This conversation is the only place I've seen issues described that are similar to what I'm experiencing.

First thing you should do is test the blanking. If you get a white screen, it's probably not going to work. If it's black, you might have a chance.

This is the exact behavior I get when I blank my jungle with nothing else connected to it, bright white screen. I was hoping you could elaborate on why this is bad/what it means. Thank you!

[benyamin39]

I finally bought a THS7315 OP amp to boost the RGB signal which I mixed with a voltage regulator and followed by a voltage divider.

The result is much better. This is definitely an RGB signal ranging from 1.7-2.1V and I believe it is possible mod this TV.



At the moment I have a lot of noise generated probably by the voltage regulator, I need to put some capacitors and probably an additional op amp to filter the signal. I ordered 2 Max4383 op amp and I will test again.

[benyamin39]

Work in progress.

I received my op amps and tested the following arrangement

https://electronics.stackexchange.com/q ... 874_568154

I think it works. I got color grades and the picture is clear despite being dull. I need to adjust the resistors to get the proper signal range, fix the noise (Not sure where it comes from this time as I did not have it before) and modify the PCB to add a switch.

[PacManPlus]

Good Morning, and forgive me for bumping an old thread.

I have two 13" Sanyo TVs, with (what looks like) the same chips involved in this thread.
Now, I watched both videos of 8-bit guy (which is what made me want to do this in the first place)...

But I was running into issues, as the schematic for the Sanyo TVs (DS13204 and DS13320) were very difficult to read, and certain traces (the 'Blanking' signal specifically) looked like it went nowhere on the board, but in the schematic they had a trace that went to the processing chip.

Also, after reading this thread, I got very discouraged with all of the hoops that we need to jump through to get this working.

However, while I had one of the TVs apart, I noticed one of the ribbon cables that went from the main circuit board to the small circuit board on the back of the tube. This ribbon cable had R,G,B, and 2 Ground lines. So I thought to myself, "Why can't I just tap into those lines, and put the sync (via composite) through the composite input?"

So I tried it. I cut the ribbon cable, and reattached them, along with external wires for R,G,B, and ground. And I couldn't believe it, but it actually worked! ... Sort of ...
Some of the colors aren't correct. In this example, I have an arcade Pac-Man board connected via R G B and the Sync going through the Composite input.

The dots are red, and Blinky and Clyde are almost indistinguishable from each other. (It looks better in the video than it actually is). In this video, I show the screen, and show exactly where I intercepted the cable going to the board on the back of the tube:
https://www.youtube.com/watch?v=zyW9WOTDc_Y

I'm guessing I have to put some resistors in-line (the signals are over-driven?), but I'm not sure of that or if I'm right what size to use.

Does anyone have any ideas?
At least if I can do this, these two TVs won't go to waste.

Thank you,
Bob

[sanyosucks]

I have a sanyo with the same jungle chip. wondering if you ever got this mod working properly? Service manual: https://www.manualslib.com/manual/69984 ... 13204.html

[tKC]

Work in progress.

I received my op amps and tested the following arrangement

https://electronics.stackexchange.com/q ... 874_568154

I think it works. I got color grades and the picture is clear despite being dull. I need to adjust the resistors to get the proper signal range, fix the noise (Not sure where it comes from this time as I did not have it before) and modify the PCB to add a switch.

I checked out your last post of Stackexchange, with what you select is your newest configurations, but appears to be settings posted by Someone else, did you use those configurations and how did it turn out?

I have the Same Jungle in a SHARP TV, and through all of testing testing trying to make this work I stumbled upon the theory of raising the voltage on the RGB lines, but decided to do more digging and happened upon your post. Di you ever try raising the voltage to 3.5Vpp?