TV RGB mod thread

[KnuckleheadFlow]

I'd still suggest finding a TV, maybe a small one, and giving it a go. It feels good making it do something it wasn't intended for. Having given the little Toshiba to my brother, it was time to move on to bigger and better things; the JVC AV-32D501 and it turned out great. I'm not sure in what way, but to me it looks better than the Toshiba. Maybe it's just the size.

Anyway, at first I couldn't find a service manual for the D501 online anywhere, even in the 13GB torrent of JVC manuals. I did find one for the D502 and it showed it had the same jungle IC as the Toshiba. Great I thought, maybe it'll be practically the same as the D501. I finally opened it up this weekend and wouldn't you know it, it is practically the same except for the jungle IC! It's got some JVC branded one which I couldn't find a data sheet for, of course. It's probably another manufacturer's but who knows which one. The micro was the same, however. I traced the RGB lines to the jungle IC, before finding a service manual for another TV that uses the exact same chassis but lacks the PiP daughter board that my TV has.

Looking at the schematics, I confirmed that I did indeed have the right pins. What was interesting was that I noticed the RGB going into the jungle IC was labled "mix RGB". It was routed first around an unpopulated header for Guide Plus (a late 90s early 00s thing like the menus you get with a digital cable box) then into and out of the PiP board. Ahhh, so what they're doing is using the same RGB inputs for OSD, Guide Plus and PiP and just muxing one on top of the other.



Testing the RGB input was as easy as pulling the PiP board and plugging the Genesis RGB into the connector, along with 5v off a regulator into the blanking ("YS") line.



Results were a near perfect RGB picture! I took some photos, but I wasn't satisfied with how those turned out TBH. I can try again later if people are interested. There's a purity or convergence issue in the upper right corner that I'll have to address but with no OSD being muxed by the PiP board I couldn't do it with the RGB input... or could I?

Long story short, I should have an LT1675 RGB mux IC Wednesday evening (with 10 more for $25 on the slow boat from Ali Express). It's actually made for things like OSD and PiP. Not only will this let me keep the the OSD overlaid with the RGB input, looking way more like it came like that from the factory, it means the 4PDT switch is no longer needed, since I think I can have the mux IC switch to overlay the OSD with the OSD's blanking signal. The LT1675 from Ali Express costs actually less than half of what I paid for my 4PDT switch too! All that'll be needed is a on/off switch for the 5V blanking.

PS - With this bigger set, I now see that my HDG non-TMSS Genesis does indeed have the dreaded jailbars. I thought I'd gotten lucky. I couldn't see them with the Toshiba and they're not that bad really, but now I can't unsee them of course. I'll have to take care of them when I re-cap it.

[FinalBaton]

I was actually also considering a JVC D-series set!
There are a couple near me (AV-27D200, AV-27D201, AV-27D500, AV-27D501) which are rated at 700 TVL, which is damn sharp for 27 inch consumer tv

[KnuckleheadFlow]

Do it. I'll check if I have the manual when I get home. Hopefully it'll be as easy as that D501.
E: The difference between the D200s and the D500s is just the PiP I think.

[FinalBaton]

have you compared how the RGB modded set's picture looks compared to using a top quality RGB-to-component transcoder on the stock component input?

[KnuckleheadFlow]

I have not. Theoretically, I know any difference should be imperceptible with a good transcoder. But part of the reason I did this was to learn more about electronics as a hobby, part of it was the DIY aspect of it (“The Man didn’t give us consumer RGB options so we’ll make our own”) and part of it was (and this is going to sound really stupid) more philosophical; the consoles generated RGB and RGB is the raw, simple, pure way of generating analogue video.
So for all this, I don’t really care for the obviously easier and more practical solutions to get great 240p.

[FinalBaton]

I agree, those are good reasons

[NJRoadfan]

One of these days, I'm going to have to try this with the 27" JVC D-Series sitting in the basement. The mod doesn't look to difficult to perform compared to some other sets.

[mvsfan]

I have an av36s33. it has the inputs for pip but doesnt have the pip board. I had kinda picked up that you might be able to feed RGB in where the pip goes but i didnt think the jungle ic supported rgb because the main inputs are component and s-video. I guess i might have been wrong.

Ill take a look at that jungle ic again and look for mix inputs.

[NJRoadfan]

The unit I have in the basement is an AV-27D503. Looking at the service manual, they completely redesigned the circuit. . Looks like the only inputs on the jungle I/C are component. RGB from the PIP board is converted by a Toshiba TA1287F before entering the chip.

[mvsfan]

yeah thats kinda what i got the first time i looked at it. Its component only.

Not that it needs anything done to it. It has great video quality as is. my snes and nes look awesome on this set.

[KnuckleheadFlow]

av36s33

AV-27D503

From a cursory glance at the schematics, unfortunately it would appear that neither of those sets can be easily modified using this method.

However, that D503 looks interesting since its PiP IC has RGB inputs and seems to have decoupling caps on them (C4316, C4317 and C4318) but the lines are going to ground. I'd be very interested in seeing if the pins are still active. If you were to remove R4315, disconnect the grounding on that PiP board connector's pins 2, 3, 4 and 5 and fed your RGB and 5V blanking in there, I wouldn't be surprised if it worked. Sure, the Toshiba TA1287F would convert it to YUV before going to the jungle, but that'd probably not mess things up too much, I'm guessing.
I'd try it if I could; if it doesn't work, just connect those lines back to ground and your TV is the same as before.

[frsj8112]

OK that makes sense. But what can I do to make the signal fit the jungle chip?

I now have a 27" Panasonic Gaoo that I'll be modifying later so I've been reading up on this. I haven't found a service manual for my set specifically yet but I have good reason to believe that its OSD RGB will also need 0.5 Vp-p. I'll do more research when I get to it, but for now I think you should look into what's called a T-pad attenuator circuit.

http://www.electronics-tutorials.ws/att ... uator.html

Hey knuckle, have you worked anything on this yet?

[KnuckleheadFlow]

I have not. But I did work out the values for a T pad attenuation circuit that should get the levels from 0.7 Vpp to 0.5 Vpp. I first did it myself after reading that link I posted earlier, then confirmed it on a couple of website calculators. The math is right, but whether or not this is the right circuit to use remains to be seen. I'm pretty sure a pi pad attenuator would also work and a simpler L pad might be sufficient. When I get to it, I'll do some testing with my oscilloscope to make sure.

Note that this is all rather new to me and it could be very wrong, but I'm trying to figure it out.

First we need to find the attenuation we need in dB. The formula for a gain or loss in Volts peak-to-peak is dB = 20*log10(Vout/Vin). Vin is 0.7, Vout is 0.5 and this worked out to -2.9225. That negative means a loss (attenuation) of 2.923 dB. Using the formula in that link (the value for the dB is given as positive since attenuation is presumed), I worked out the following values for the T pad circuit. Confirmed it here too. You would connect this on each RGB input, before the usual 75 Ω termination to ground, I think. I'm also not sure where the decoupling caps should go because I can see them needing to be before R1, but I can see it also not mattering. Again, I'll have to do testing. Or you can, of course!

Code: Select all

RGB source ---[R1 12.5 Ω]-- --[R2 12.5 Ω]-- --- RGB in
                           |               |
                           |               |
                       [R3 219 Ω]      [R4 75 Ω]???
                           |               |
                            -----[GND]-----

With SMD resistors, I found it more economical to buy smaller values to use in series. For R1 and R2, a 2.5 Ω in series with a 10 Ω, and for R3, 169 Ω in series with 50 Ω, worked out to be significantly less than actual 12.5 Ω and 219 Ω resistors.

Along the same lines, here's how a pi attenuator would look.

Code: Select all

RGB source -- --[R1 26 Ω]---- --------- --- RGB in
             |               |         |
             |               |         |
        [R2 450 Ω]      [R3 450 Ω] [R4 75 Ω]???
             |               |         | 
              -----[GND]----- ---------

[suprcrackers]

Hey I would like to thank Voultar for setting the host of the Retrorgb podcast straight when it comes to RGB modified CRT's vs BVM/PVM's. I completely share his opinion that yes a BVM is of better quality. But why would I want to pay upwards of $300 to play on a 20" BVM when I can for $5 play on a 27"-36" modified CRT with close to the same results? I have been listening to the host rag on modified RGB CRT's for too long.

Good work my friend!

[mikejmoffitt]

One of these days, I'm going to have to try this with the 27" JVC D-Series sitting in the basement. The mod doesn't look to difficult to perform compared to some other sets.

The D-series was the first one I ever did, and those work very well:



http://mikejmoffitt.com/articles/0032-tvrgb.html

[KnuckleheadFlow]

Hey I would like to thank Voultar for setting the host of the Retrorgb podcast straight when it comes to RGB modified CRT's vs BVM/PVM's. I completely share his opinion that yes a BVM is of better quality. But why would I want to pay upwards of $300 to play on a 20" BVM when I can for $5 play on a 27"-36" modified CRT with close to the same results? I have been listening to the host rag on modified RGB CRT's for too long.

Good work my friend!

The retrorgb guy rags on modified TVs with regularity? With BS reasons? I'd like to hear this actually, when was this one?

[suprcrackers]

Maybe rag is too strong of a term. He has mentioned on 2-3 podcasts that I can remember on how the sony PVM/BVM is superior to a RGB modified CRT.

The thing is I don't have a BVM or a PVM to compare it because

a)I live in a rural area. So when the whole craze started I had no access to them.

b) Now that the craze has been going for a many years now, I can not buy them economically. I am not going to drop close to $300 on a 20" BVM so I can feel smug in knowing I have the absolute crispest picture for my games. I would much rather pick up a nice 27-36 inch Trinitron for free, spend a couple dollars in caps, wiring, a switch, a socket, and enjoy gaming on a very close proximity when it comes to clarity. But the also have the added bonus of playing on a much much larger screen.

It just annoys me, that's all.

[Guspaz]

Well, he's right, a decent PVM is going to be sharper since it's going to have a higher TVL count and use better phosphors. That doesn't mean that an RGB-modded CRT isn't good too, it's just not as high quality of a device...

[vol.2]

Wondering if it makes sense to RGB mod one of these: kv-32hs510

I have this TV, and while it does a great job with 480p material, as I understand it, it automatically treats 240p content as 480i. (I'm still not 100% sure about this, but I have read about it on other forums, and there is a youtube game channel that mentions it as well)
The TV already has a component in but, as I mentioned, it displays 240p as 480i. I think the component in goes to a digital processing unit of some kind that converts non-native resolutions to their nearest neighbor or something.

In terms of do-ability, I have the service manual. I can do electronics work, and I am experienced with soldering and PCBS. I actually build circuits at work sometimes, and I have experience working on audio equipment like amplifiers, etc, but I have never worked on a TV, so I would be a bit new to all of that.

What I am hoping for, is that someone can tell me if this would be worth it. Is it even doable at all? Am I correct in thinking that this massive 1080i CRT from the last few years of SONY EDTV/HDTVs probably has a higher than average vertical line count?

[KnuckleheadFlow]

I'm almost sure that an EDTV will have a single chip jungle IC/MCU combination, therefore no RGB lines in between to tap into. If so, the only way to get RGB going would be to drive the electron guns directly. Not nearly as simple from what I understand.

[cruzlink2]

Hi guys got a question that hopefully someone with more experience could answer. I modded 2 TVs so far one was an old 90's RCA tube and had only one composite input, I hooked up the sync to the luma pin on the jungle IC and it handle's any sync I've thrown at it so far. My question is about the second TV I modded, a newer sharp 2006 tube with 3 composite, one Svideo and one component input I used the composite the first composite pin for sync and attempted to do a dpdt switch to use luma on the svideo in case I needed it. The compsosite video input works but when I try using the luma pin it doesn't work. Was wondering if maybe the TV might have an enable pin on the Svideo port that tells it when a cable is plugged in and allowing sync to be fed to luma pin. By the way the svideo and composite video input share the video 1 input, that led me to believe there has to be an enable pin. Anyone else encountered this?

[KnuckleheadFlow]

Well, he's right, a decent PVM is going to be sharper since it's going to have a higher TVL count and use better phosphors. That doesn't mean that an RGB-modded CRT isn't good too, it's just not as high quality of a device...

Oh, no question. I've never seen one in person but I'm sure I'd still love a P/BVM (or any other pro RGB)... if it was big enough, not used up and priced right. And available.
A couple of months back, I actually did find a PVM for a price I was willing to pay, one of these. It doesn't power on, so it's in the projects queue.

[suprcrackers]

I agree. My problem this whole time hasn't been that I disagree with the fact that PVM/BVMs are better. It's just saying it so flippantly without explaining the obvious size and price difference which obviously should come into play, that feels wrong.

[thebeautifulones]

I'm planning on modding a Panasonic ct-27xf11cs.

This is the IC I'm looking at http://pdf.datasheetcatalog.com/datashe ... N5307K.pdf

Can someone tell me if this seems right?

1. lift the OSD RGB pins (22, 23, 24)
2. solder scart socket RGB to 75ohm resistors and ground the resistors, to ie. pin 27
3. solder 0.1uf caps between the resistors and the IC's RGB pins (edit: it looks like I may need to attenuate 0.7 to 0.5?)
4. connect Ys input (pin 21) to a 5v source, ie. pin 37
5. solder c-sync from scart socket to composite video input of TV

I'm especially wondering about step 4. Is that the blanking pin?

[KnuckleheadFlow]

Yes those are the pins and yes, it looks like a 0.5 Vpp RGB signal is needed. Now, I wrote a bunch of stuff about attenuators a bit ago but it could be as simple as using a resistor in series with the RGB input. I was planning experimenting using a few pots (100 Ohm?) once it's time to mod my own Panasonic (ct-27xf34c) and read up on video attentuation.

And from the electrical characteristics on that pdf's page 9 (page 231 in the scanned original I guess) it'd appear that Ys (pin 21, blanking) only needs 1 V. Not sure what 5 V would do but I'd look into using a linear regulator (like this one, costs about $3 http://www.ti.com/product/lp3879/description) if there isn't a 1 V source handy.

[KnuckleheadFlow]

Wow, do I feel stupid. If your TV's jungle IC needs it, going from 0.7 Vpp to 0.5 Vpp is dead simple. Looking for video attenuation examples I realized that superguns with SCART connectors need to do this to drop the ~3 Vpp JAMMA RGB to 0.7 Vpp.
I had a look at this guy's supergun and long story short, a 30 Ω resistor in series with the RGB input before the 75 Ω terminations will make a voltage divider that'll attenuate the typical console's 0.7 Vpp to 0.5 Vpp.

My reasoning being that in the above supergun we've got:

Code: Select all

JAMMA RGB in (3 Vpp) ---[R1 180Ω]---[optional 250Ω pot]--- --- AD8073 amps then SCART RGB out (0.7Vpp)
                                                          |
                                                          |--- AD725 encoder IC
                                                          |
                                                       [R2 75Ω]
                                                          |
                                                          |
                                                         GND

For our purposes we can ignore the AD8073 amplifiers (probably) since that's accounting for the RGB being split to his encoder IC (AD725) and SCART connector. All that matters is the voltage divider. A regular resistive voltage divider is:

Code: Select all

V in ---[R1]--- --- V out
               |
              [R2]
               |
              GND

with
V out = R2/R1+R2 * V in

So with that supergun, R1 is 180 Ω (+ optional 250 Ω pot) and R2 is 75Ω to go from 2.3 Vpp (I guess that's the typical JAMMA RGB signal and the pots are there for stronger boards sending 3 V?) to 0.7 Vpp. Our R2 will also be 75 Ω and we want to go from 0.7 V in to 0.5 V out so...

Code: Select all

0.5 V = (75Ω / xΩ + 75Ω) * 0.7 V
...
x = 30Ω

Add a pot along with that 30 Ω resistor in case you get something with stronger signals and Bob's your uncle. It's really simple and I'm surprised it took me this long to figure out.

[cruzlink2]

Hey guys, trying to do my third mod for a friend. His jungle ic generates osd internally but there is a set of pins 46 47 48 that are unused. They are labeled rgb/yuv insert couuld these be used and what would be my blanking pin pin 49?

[mikejmoffitt]

I have a chance to get a 36" Trinitron, from the same vintage as my KV-27S42. Think I should pick it up? It's free.

[KnuckleheadFlow]

Ha you honestly think anyone in this thread would tell you no?
Only reasons I see not to is if I knew I couldn't mod it, it had some flaw not worth fixing like screen burn, or I didn't have the room. Worst case scenario you gotta ditch a big TV.

[thebeautifulones]

Thanks a lot for the info, Knucklehead. Going to order the resistors.