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 Post subject: Re: TV RGB mod thread
PostPosted: Tue Feb 23, 2021 8:39 pm 



Joined: 10 Dec 2020
Posts: 1
I recently picked up an Akai CFT2490 after seeing some discussion about that model here in this thread. I was able to find a service manual for the TV, and learned that it's actually a rebadged Samsung (specifically a CFT24907X/SMS). As discussed earlier in this thread, the A/V connectors on this TV are actually a SCART connector on the mainboard, and it was super simple to get the RCA jacks removed and a SCART socket installed in their place.
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The service manual indicates that the resistor on SCART pin 8 (R717, physically missing from the board) should be a 39K resistor, which is also one of the values that MarkOzLad worked out assuming that R715 is part of a voltage divider for that line (again, earlier in this thread).
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I soldered one on and tested out some games, and the results were pretty good!
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However, the TV did not switch to the SCART input when powering on a console. I know that the consoles I was using output 5V on pin 8 instead of the 12V that the TV is presumably expecting, so I tried swapping out the 39K resistor for a 10K resistor. (I'm no electrical engineer, but a voltage divider calculator indicates that I would get the same resulting voltage that way.) This also doesn't seem to have done anything to get the TV to automatically switch inputs. If I had to guess, I'd say that since this model was sold in the US, its firmware probably just doesn't do anything with the input from SCART pin 8. Pin 16 connects directly to the RGB Enable pin of the jungle chip, so as long as the TV is set to the right input, I'd be willing to bet that it would work just fine even without any connection on pin 8 at all.

The TV itself has some geometry issues that the service menu doesn't seem able to fix, specifically with some uneven line lengths down the height of the screen, as well as stretching toward the left and right edges of the screen (which I understand is partially, if not fully, due to the fact that it's a flat-screen CRT.) I'm considering recapping the whole mainboard, since I've read that it can help with geometry issues like that, but it's definitely uncharted territory for me, so I'm keeping my expectations pretty low.

That aside, though, I'm still real happy with it! It's satisfying to be able to do such a simple mod to get a great picture out of a TV I paid $5 for.


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 Post subject: Re: TV RGB mod thread
PostPosted: Tue Feb 23, 2021 10:17 pm 


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BazookaBen wrote:
Yeah I don't know if we should have separate threads for component and/or s-video/composite mods. There is tons of crossover in the knowledge related to doing this stuff though.

Related to component mods: In the datasheet CXA2135s jungle, which I think is practically identical to my CXA2131AS that I don't have a datasheet for, it says this about the 2nd set of RGB inputs:

Quote:
R2,G2 and B2 signal input. Input a 0.7Vp-p (no sync,100IRE) signal via a 0.01F capacitor. Same as RGB1 IN, the input signal is clamped at the burst timing in SCP. When setting the bus YUVOUT=1 and connecting 10k resistors to Vcc, Internal YUV signals outputs
30 Pin: B-Y output
31 Pin: R-Y output
32 Pin: Y output


Not sure if this means it can also be component, and the using the word output is confusing me. Can an input be switched to an output inside the jungle?


Not quite, the jungle chip has dedicated YUV inputs on pins 37-39. They are used for the PIP board on some models. There are some quirks, but overall I think the mod works better than the usual OSD method. The TVs I've tried all use the CXA2133s chip, for which I couldn't find a datasheet either; I was going off the CXA2061s which seems to be mostly the same.

I'll write something up later this afternoon. I think I will make a separate post. It's still a bit of a WIP and it would be easier to share ideas without everybody else's RGB mod questions getting in the way (and vice versa).


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 Post subject: Re: TV RGB mod thread
PostPosted: Tue Feb 23, 2021 10:45 pm 


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FantasticMrSocks wrote:
The TV itself has some geometry issues that the service menu doesn't seem able to fix, specifically with some uneven line lengths down the height of the screen, as well as stretching toward the left and right edges of the screen (which I understand is partially, if not fully, due to the fact that it's a flat-screen CRT.) I'm considering recapping the whole mainboard, since I've read that it can help with geometry issues like that, but it's definitely uncharted territory for me, so I'm keeping my expectations pretty low.


I'm not sure about the auto-detect on Scart input. I guess if you have it working by switching it on the remote, then it's probably fine, right?

The geometry issues sound like it might be vertical linearity. If you can't access that in the service menu, it would be worth looking around on the motherboard. In fact, if you can find any physical geometry controls at all, it's probably best to set the service menu at mid-way and adjust the physical pots until it generally looks good.

IAC, to adjust linearity, you'll need the grid pattern, and you can measure the height of the boxes in the grid, adjusting to make them all as equal as possible from top to bottom.

You can narrow down caps that you might want to replace by sections on the board. The flat screen CRTs are more difficult, and I don't think caps are always the problem there. Sometimes the LOPT gets weak, or some other part of the system starts to wear. However, you can probably improve the geometry at least a little by checking and replacing any out of value (20% or more) caps in the Horizontal and Vertical sections, and anything electrolytic that's directly coupled to the LOPT (if there is any).

You don't need to mess with anything in the control electronics or the tuner section as that stuff is probably fine and doesn't see much heat or wear. the most suspect things are small caps that are near hot component, as those tend to dry out. That's mostly around the HV, and the power section near any big transistors/heat sinks or any banks of power resistors, and especially anything near a spot on the PCB that looks burn in any way.


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 Post subject: Re: TV RGB mod thread
PostPosted: Wed Feb 24, 2021 12:02 pm 


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I wrote a post about the Trinitron component mod, for those interested:

https://shmups.system11.org/viewtopic.php?f=6&t=68134


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 Post subject: Re: TV RGB mod thread
PostPosted: Fri Feb 26, 2021 7:49 am 



Joined: 26 Feb 2021
Posts: 4
Location: Seattle
I picked up a Philips 19PS35 (Chasis code 19S800 7628) the other day with the intention of making it my first RGB mod, but I'm having a hard time figuring out the best way to go about this. There's only a single chip that seems to handle everything including the OSD, which I wasn't really expecting. The IC is a TDA9577H, which I can't seem to find a datasheet explicitly for, but I did find one for a TDA9570H, and from looking at it and other TDA95xx datasheets, it appears to be the same as other TDA95xx IC's.
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I also managed to find the service manual for the chassis and I noticed that it has unused pins for component or RGB, but I'm not actually sure if I can piggyback off of those in any way.
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Attached below are images of the IC side of the board and the unpopulated part of the PCB where other inputs would be
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Image


As it stands this unit only has RF input on the rear and composite on the front, so I'm open to any advice on how I could go about adding higher-quality inputs to this unit.

Thank you!


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 Post subject: Re: TV RGB mod thread
PostPosted: Fri Feb 26, 2021 11:21 pm 


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You probably can't do an RGB mod on your philips. But you should be able to add component and/or Svideo. Go back to page 119 of this thread and there are a few posts about it. Another user and I did this mod to a Magnavox TV that's similar to yours.

The extra video inputs are disabled in software, but usually can be activated in the service menu.


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 Post subject: Re: TV RGB mod thread
PostPosted: Sat Feb 27, 2021 12:49 am 



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Posts: 213
I have actually RGB modded a set that uses that same family of microprocessor (TDA957x series).

It's possible, but you need to access the service menu and change certain values. Tell me if you can access the service menu somehow. Here's the datasheet:
https://pt.scribd.com/document/67809217 ... HDatasheet

I recommend RGB over Component in this case because this chip wont get sync from the Luma line without flashing the EEPROM.


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 Post subject: Re: TV RGB mod thread
PostPosted: Sat Feb 27, 2021 3:41 am 



Joined: 26 Feb 2021
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It looks like I'd need a master setup remote to enter the service menu, so I just ordered an Anderic RR2573 master setup remote that should hopefully do the job.

tongshadow wrote:
I have actually RGB modded a set that uses that same family of microprocessor (TDA957x series).

How did you go about wiring yours up? I've been trying to come up with a good way to feed in RGB but I've got nothing thus far.

I'm also trying to come up with a way to get composite onto the back of the TV, it's seeming like the easiest way would just be to desolder the front jack and feed it to the rear, but I'm not sure if there's a cleaner way to handle it.


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 Post subject: Re: TV RGB mod thread
PostPosted: Sat Feb 27, 2021 5:37 am 


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tongshadow wrote:
I have actually RGB modded a set that uses that same family of microprocessor (TDA957x series).

It's possible, but you need to access the service menu and change certain values. Tell me if you can access the service menu somehow. Here's the datasheet:
https://pt.scribd.com/document/67809217 ... HDatasheet

I recommend RGB over Component in this case because this chip wont get sync from the Luma line without flashing the EEPROM.


Nice! What settings did you use for the option bits?


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 Post subject: Re: TV RGB mod thread
PostPosted: Sat Feb 27, 2021 2:12 pm 



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SnarkyRaccoon wrote:
It looks like I'd need a master setup remote to enter the service menu, so I just ordered an Anderic RR2573 master setup remote that should hopefully do the job.

tongshadow wrote:
I have actually RGB modded a set that uses that same family of microprocessor (TDA957x series).

How did you go about wiring yours up? I've been trying to come up with a good way to feed in RGB but I've got nothing thus far.

I'm also trying to come up with a way to get composite onto the back of the TV, it's seeming like the easiest way would just be to desolder the front jack and feed it to the rear, but I'm not sure if there's a cleaner way to handle it.

You're gonna work on pins 50~53. First you need to see if the RGB inputs are populated by grounded SMD capacitors, if yes, you'll need to remove them. Pin 50 is the insertion pin, which is fed by 3.3v that goes through 2 resistors. It's basically digital blanking.

This is how you wire them:
https://i.imgur.com/FYP8vJt.png
You can use between 10nF (103) and 100nF (104) ceramic capacitors, they dont have to be SMD btw.

The hardest part is getting a proper connector for RGB. Your sync signal will come from the Composite input.
Then you enable RGB Blanking and RGB mode through the service menu:
https://i.imgur.com/4OESUpz.png
https://i.imgur.com/OSpUslc.png

The addresses are called "Control 0" and "Control 1", you change the values to 64~74" and "2", respectively. For the latter you can try different values if you dont see RGB. That was the case for my set, but since the Microprocessor is the same it should be similar or identical.

matt wrote:
Nice! What settings did you use for the option bits?

Control 0 to 72, from default 8.
Control 1 to 2, from default 0.


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 Post subject: Re: TV RGB mod thread
PostPosted: Sat Feb 27, 2021 5:29 pm 



Joined: 26 Feb 2021
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This is some really good information, thanks! I've just ordered up everything I think I'll need to do the mod, so I'll report back when I'm hopefully done with the hardware portion of the mod!


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 Post subject: Re: TV RGB mod thread
PostPosted: Mon Mar 01, 2021 10:40 pm 


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Hi, I don't know much about the inter-workings of CRTs so bear with me.

I'm trying to RGB mod a crappy Sylvania SST413 TV.
It is to my understanding that I need to pump an RGB signal into the video processor (JUNGLE IC) on my TVs board, more specifically the lanes intended for the OSD, and put 5V on the blanking lane whenever I want to display my signal. Also I figured out my video processor seems to require a 75 ohm resistor and a 0.1uF capacitor (just like the diagram in the OP said).
What I'm trying to figure out if it is acceptable to leave the OSD microprocessors RGB and blanking legs intact, or if I absolutely HAVE to remove them in order for my RGB signal to display properly.

Thanks, also please correct me if I got anything wrong there :D .


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 Post subject: Re: TV RGB mod thread
PostPosted: Mon Mar 01, 2021 11:41 pm 



Joined: 07 Jan 2017
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NeonOverflow wrote:
What I'm trying to figure out if it is acceptable to leave the OSD microprocessors RGB and blanking legs intact, or if I absolutely HAVE to remove them in order for my RGB signal to display properly.

Thanks, also please correct me if I got anything wrong there :D .

You can just remove the component that is positioned just before the legs and add it later to the switch.


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 Post subject: Re: TV RGB mod thread
PostPosted: Tue Mar 02, 2021 12:36 am 


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tongshadow wrote:
NeonOverflow wrote:
What I'm trying to figure out if it is acceptable to leave the OSD microprocessors RGB and blanking legs intact, or if I absolutely HAVE to remove them in order for my RGB signal to display properly.

Thanks, also please correct me if I got anything wrong there :D .

You can just remove the component that is positioned just before the legs and add it later to the switch.


Would that entail getting multiple switches?


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 Post subject: Re: TV RGB mod thread
PostPosted: Tue Mar 02, 2021 12:58 am 



Joined: 07 Jan 2017
Posts: 213
It's like this:
https://youtu.be/jbi9HEz-cww?t=426

Or you can use the MUX method, not sure if it would work in your case though:
https://i.imgur.com/dKnPBC9.png


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 Post subject: Re: TV RGB mod thread
PostPosted: Tue Mar 02, 2021 8:15 am 



Joined: 02 Jan 2021
Posts: 5
Hi guys, trying to add RGB to a Sharp 20F640, tried searching to see if anyone has done this particular model or even variants on the chassis, but no luck. There is a space for a header on the board between the MICOM and jungle chip labeled RGB, and looking at another model (although with slightly different chipsets) there does seem to be a use for this jumper. I am completely confident in my soldering skills if someone could explain out a circuit I need to put in to get this to work, but I have no idea on how to figure what resistors or capacitors need to go where. Hoping this is a easy one. Attached some pictures if they're of any help.

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On the flip side, I may be picking up 2 SSM-14N5U's (and maybe even more) from my states airport post office that I just happened to come across while on a job on property (Fire Alarm Tech). Looks like they're finally getting rid of their security monitors and I'm hoping there isn't too much use on them. But considering I'm in Hawaii and getting a PVM shipped here is next to impossible to do cheaply, ill take what I can.
I plan on using an established guide on those to enable the already built in RGB capabilities since they're pretty much trimmed down PVM-14N5U's which in itself are trimmed down PVM-14N6U's. Super stoked for that if I can take possession of them.


Last edited by shikikanzero on Sat Mar 06, 2021 10:36 pm, edited 1 time in total.

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 Post subject: Re: TV RGB mod thread
PostPosted: Tue Mar 02, 2021 4:00 pm 



Joined: 11 Jan 2021
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SnarkyRaccoon wrote:
I also managed to find the service manual for the chassis and I noticed that it has unused pins for component or RGB, but I'm not actually sure if I can piggyback off of those in any way.
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This is the aid that I have been using for my work on the 937x series chip. Look at the Yellow box for YUV pin 51-53 input. The Teal box for blanking pin 50.
https://i.imgur.com/zeKvwsN.jpeg


SnarkyRaccoon wrote:
Attached below are images of the IC side of the board and the unpopulated part of the PCB where other inputs would be
Spoiler: show
Image
Image


As it stands this unit only has RF input on the rear and composite on the front, so I'm open to any advice on how I could go about adding higher-quality inputs to this unit.

Thank you!

This pic looks similar to the board you posted. Following the traces I see a set of unpopulated SMD components on the lines. For me it is easier to fill these in and follow the line to a thru hole jumper and lift that to inject the signal, rather than working directly on the pins of the IC chip.
https://i.imgur.com/m0ge9dj.jpeg
https://i.imgur.com/UWXVlEG.jpeg

Again, these are visual aids for a 20pt6331, Chasis L01.1U, but the pins are numbered the same.


Last edited by stonesipping on Sat Mar 06, 2021 9:14 am, edited 1 time in total.

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 Post subject: Re: TV RGB mod thread
PostPosted: Wed Mar 03, 2021 4:34 pm 


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I'm running into color calibration issues on my Sony WEGA KV-24FS120 over Component and am wondering if there's any benefit to RGB modding it?

Is it possible to RGB mod these?

Does RGB modding bypass the internal color processing that's throwing my colors off?

Do you lose access to the built-in Gain/Bias adjustments after RGB modding?

Is it possible to use the existing component and one of the composite ports for RGBS?

Thanks!


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 Post subject: Re: TV RGB mod thread
PostPosted: Thu Mar 04, 2021 5:28 am 


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No, the 24fs120 can't be RGB modded. It has a 1 chip design with no place for RGB input.


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 Post subject: Re: TV RGB mod thread
PostPosted: Thu Mar 04, 2021 8:36 am 



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I managed to screw up pretty badly; I lifted the pad I was originally going to use for the red input, decided to try just taking it straight to leg of the IC instead, and somehow managed to completely remove the leg from the IC. I'm thinking my best bet now if I want to salvage this is going to be a new chip. My board has a TDA9577H/N1/A/0818 and the closest thing I can find is a TDA9577H/N1/A/1057, which seems to be used in the 7638 chassis while mine is a 7628. I'm tempted to buy one to see if it works (and to finally give myself an excuse to invest in a hot air rework station), but not sure if it would actually be a suitable replacement.


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 Post subject: Re: TV RGB mod thread
PostPosted: Thu Mar 04, 2021 10:57 am 



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You could also try carefully filing or Dremeling into the package of the IC to expose more of the leg going to the actual chip on the inside.
When I modded my 1-Chip SNES I also accidentally broke off a pin and had to resort to that technique. Your chip seems to be of a similar size so it might just work.


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 Post subject: Re: TV RGB mod thread
PostPosted: Thu Mar 04, 2021 3:47 pm 


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SnarkyRaccoon wrote:
My board has a TDA9577H/N1/A/0818 and the closest thing I can find is a TDA9577H/N1/A/1057, which seems to be used in the 7638 chassis while mine is a 7628. I'm tempted to buy one to see if it works (and to finally give myself an excuse to invest in a hot air rework station), but not sure if it would actually be a suitable replacement.


I can't find the datasheets, so chances are you can't either. Next best bet is to compare the pins on the schematics to see if they look identical. Service manuals usually have a basic block pinout of the main ICs, but if you can't find that, just compare the actual schematics and write down all the names on each pin. If the two are the same, it's a good chance the extra numbers are not important or one is an updated version of the other.

There's another possibility, and that's the extra numbers have to do with the package. They often make chips that function the same, but come in different sizes or shapes. If that's the case, you will have to solder the new chip to a breakout board and then wire that board to the correct pads on the PCB.

As the other post mentioned, you can try to dremel out or carefully drill the edge of the chip to expose the leg and solder to it. Can't hurt to try.


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 Post subject: Re: TV RGB mod thread
PostPosted: Thu Mar 04, 2021 7:55 pm 



Joined: 07 Jan 2017
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Never try to lift SMD legs, they break very easily! You could have just scratched the nearest trace into the chip to expose the board's copper and soldered into it.

https://www.youtube.com/watch?v=xty1G5UBYb0


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 Post subject: Re: TV RGB mod thread
PostPosted: Sat Mar 06, 2021 10:38 pm 



Joined: 02 Jan 2021
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anyone able to help with this one? is it possible it is set up for RGB already and i just gotta wire in some BNC's to that RGB header and some blanking voltage?

shikikanzero wrote:
Hi guys, trying to add RGB to a Sharp 20F640, tried searching to see if anyone has done this particular model or even variants on the chassis, but no luck. There is a space for a header on the board between the MICOM and jungle chip labeled RGB, and looking at another model (although with slightly different chipsets) there does seem to be a use for this jumper. I am completely confident in my soldering skills if someone could explain out a circuit I need to put in to get this to work, but I have no idea on how to figure what resistors or capacitors need to go where. Hoping this is a easy one. Attached some pictures if they're of any help.

Spoiler: show
Image

Spoiler: show
Image

Spoiler: show
Image

Spoiler: show
Image

On the flip side, I may be picking up 2 SSM-14N5U's (and maybe even more) from my states airport post office that I just happened to come across while on a job on property (Fire Alarm Tech). Looks like they're finally getting rid of their security monitors and I'm hoping there isn't too much use on them. But considering I'm in Hawaii and getting a PVM shipped here is next to impossible to do cheaply, ill take what I can.
I plan on using an established guide on those to enable the already built in RGB capabilities since they're pretty much trimmed down PVM-14N5U's which in itself are trimmed down PVM-14N6U's. Super stoked for that if I can take possession of them.


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 Post subject: Re: TV RGB mod thread
PostPosted: Sat Mar 06, 2021 11:42 pm 


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shikikanzero wrote:
anyone able to help with this one? is it possible it is set up for RGB already and i just gotta wire in some BNC's to that RGB header and some blanking voltage?


Maybe. It looks like there are RGB inputs, but you only posted a small amount of the schematic. I think you're not getting an answer because it's not enough to work from. Post pictures of the signal path between the OSD source and the jungle IC and ideally also the pinout of the two ICs.


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 Post subject: Re: TV RGB mod thread
PostPosted: Sat Mar 06, 2021 11:53 pm 



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vol.2 wrote:
shikikanzero wrote:
anyone able to help with this one? is it possible it is set up for RGB already and i just gotta wire in some BNC's to that RGB header and some blanking voltage?


Maybe. It looks like there are RGB inputs, but you only posted a small amount of the schematic. I think you're not getting an answer because it's not enough to work from. Post pictures of the signal path between the OSD source and the jungle IC and ideally also the pinout of the two ICs.


thanks for the reply, here they are.


Spoiler: show
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 Post subject: Re: TV RGB mod thread
PostPosted: Sun Mar 07, 2021 2:22 am 


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shikikanzero wrote:

thanks for the reply, here they are.

Spoiler: show
Image

Spoiler: show
Image


Looking at that, it's a bit different from what I'm used to seeing. One issue I can think of is what the OSD input on the Jungle IC is expecting (TTL or analog) and whether or not you can do it without level shifting the input.

What I see on the schematic is Zero Volts DC coming out of the OSD output on the character generation chip and roughly 2.3VDC on the OSD inputs on the Jungle IC. I also do not see any DC restoration circuit in between the two lines, or a level shift chip. I see 2.3VDC coming out of the Jungle IC RGB outputs that are going to the neck board. That might suggest that the OSD is directly coupled to the RGB output and the RGB input voltage level simply reflects the output voltage level (because they are just joined at that point) and the caps and resistors between the Char Gen IC and the Jungle IC are there to just block the DC offset in the direction of the character IC.

So, that's suspicious. I would like confirmation from someone else here, but I kind of would guess that might be digital RGB, and I'm not sure how to handle that.

To answer the question you had in your first post about an unused RGB input. No, I don't see any other RGB inputs on the Jungle IC, only the Char Gen IC RGB input. There's inputs for the composite video and the NTSC/PAL signals. This set is different from other ones I've seen in that it does the IF input on the jungle IC, and seems to maybe use the Char Gen IC for some other stuff as well.

Sorry I couldn't be more help than that, but I feel confident that someone else here can fill in the blanks about the OSD RGB inputs there.


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 Post subject: Re: TV RGB mod thread
PostPosted: Sun Mar 07, 2021 3:15 am 


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shikikanzero wrote:
Hi guys, trying to add RGB to a Sharp 20F640, tried searching to see if anyone has done this particular model or even variants on the chassis, but no luck. There is a space for a header on the board between the MICOM and jungle chip labeled RGB, and looking at another model (although with slightly different chipsets) there does seem to be a use for this jumper. I am completely confident in my soldering skills if someone could explain out a circuit I need to put in to get this to work, but I have no idea on how to figure what resistors or capacitors need to go where. Hoping this is a easy one. Attached some pictures if they're of any help.


Sorry I missed this when you posted it. Always nice to see other people here from Hawaii. What island are you on? I've done a number of RGB mods and am happy to help if you're on Oahu.

Here's the data sheet for your jungle chip if you didn't find it already:
https://datasheetspdf.com/pdf/610984/Re ... 61251AFP/1

It's very similar to the jungle chips used by the Toshiba AF series, which usually do well with RGB mods and have been documented pretty well. The chip can be set to take digital or analog RGB, but fortunately the schematic looks like a typical circuit for analog inputs so I think it would work. The usual OSD mix method should work fine. Have you looked up MarkOZLad's posts on the subject?

vol.2 wrote:
What I see on the schematic is Zero Volts DC coming out of the OSD output on the character generation chip and roughly 2.3VDC on the OSD inputs on the Jungle IC. I also do not see any DC restoration circuit in between the two lines, or a level shift chip. I see 2.3VDC coming out of the Jungle IC RGB outputs that are going to the neck board. That might suggest that the OSD is directly coupled to the RGB output and the RGB input voltage level simply reflects the output voltage level (because they are just joined at that point) and the caps and resistors between the Char Gen IC and the Jungle IC are there to just block the DC offset in the direction of the character IC.


I don't think this is out of the ordinary. According to its data sheet, the jungle chip expects 0.7pp RGB in analog mode and 1vpp for digital. 2.3v on the input is pretty normal for OSD signals, and I think the 0v on the Micon outputs is an irreguarity with the schematic.


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 Post subject: Re: TV RGB mod thread
PostPosted: Sun Mar 07, 2021 9:24 am 


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Location: Honolulu, Hawaii
shikikanzero wrote:
There is a space for a header on the board between the MICOM and jungle chip labeled RGB, and looking at another model (although with slightly different chipsets) there does seem to be a use for this jumper.


I took another look at your TV's service manual. It looks like this header is just what you need - it connects to all 3 of the OSD RGB lines and the blanking pin (pins 1-4 are B, G, R, and blanking respectively). If you populate this header you'll have access to all 4 of the signals you need from the top of the PCB, which simplifies things a lot.

If you haven't seen it already, the OSD mixing circuit is pretty easy to follow:

Spoiler: show
Image


For your TV, you'll have to remove resistors R1068, R1070, and R1075. The RGB lines will each need a 75 ohm terminating resistor to ground, and a 180 ohm inline resistor before they connect to the header (you might have to try a few different values for this one to get the OSD brightness right). For my mods I usually just put these on the RGB input connector and run the wires from there. For blanking, you'll have to find a +5v source on the PCB and run it through a switch to pin 4 of the header (I usually add a 1k resistor for safety). I couldn't find a voltage listed for the blanking pin on your jungle chip's data sheet, but +5v has worked fine for other Renesas chips so it should be OK.


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 Post subject: Re: TV RGB mod thread
PostPosted: Sun Mar 07, 2021 10:03 am 



Joined: 02 Jan 2021
Posts: 5
matt wrote:
Sorry I missed this when you posted it. Always nice to see other people here from Hawaii. What island are you on? I've done a number of RGB mods and am happy to help if you're on Oahu.

Here's the data sheet for your jungle chip if you didn't find it already:
https://datasheetspdf.com/pdf/610984/Re ... 61251AFP/1

It's very similar to the jungle chips used by the Toshiba AF series, which usually do well with RGB mods and have been documented pretty well. The chip can be set to take digital or analog RGB, but fortunately the schematic looks like a typical circuit for analog inputs so I think it would work. The usual OSD mix method should work fine. Have you looked up MarkOZLad's posts on the subject?

vol.2 wrote:
What I see on the schematic is Zero Volts DC coming out of the OSD output on the character generation chip and roughly 2.3VDC on the OSD inputs on the Jungle IC. I also do not see any DC restoration circuit in between the two lines, or a level shift chip. I see 2.3VDC coming out of the Jungle IC RGB outputs that are going to the neck board. That might suggest that the OSD is directly coupled to the RGB output and the RGB input voltage level simply reflects the output voltage level (because they are just joined at that point) and the caps and resistors between the Char Gen IC and the Jungle IC are there to just block the DC offset in the direction of the character IC.


I don't think this is out of the ordinary. According to its data sheet, the jungle chip expects 0.7pp RGB in analog mode and 1vpp for digital. 2.3v on the input is pretty normal for OSD signals, and I think the 0v on the Micon outputs is an irregularity with the schematic.


Nah, thank you for doing the community a service, its not like you have to reply to everyone asking for help, so really appreciate it.

I actually am on Oahu. I have read through quite a bit of this thread, and while I do get the circuit that needs to be built, I have no idea how you guys determine when and where you need resistors or capacitors, and at what values, and what they even do for the circuit as far as its relation to the signal. I have seen that spec sheet for the Renesas chip before, and other than the pinouts, I wasn't able to absorb much from it.

Though with the information you gave me, I now think I figured out how to use MarkOZLad's resistor chart. Looks like ill need to

Remove the 330ohm resistors to ground for RGB
Add 180ohm resistors in series after the 330ohm resistors on the RGB lines
add 75ohm resistors to ground before the 180ohm resistors

Hoping I'm right here. Would I be getting sync on composite? And as for the blanking voltage, how much and would it be before or after the 560 ohm resistor? I've reviewed some Toshiba AF series RGB mods (from The SegaHolic and Analog Thinker, specifically) but not sure if I should be using the same reference voltages they used on their Toshiba sets.


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