Sony Trinitron S-Video/Composite Mod (RF-Only TV) SOLVED

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d32xing
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Re: Sony Trinitron S-Video Mod

Post by d32xing »

Will this work on an NTSC-U unit? I have a similar TV but it's a TS20 like a user stated above. And the red X means eliminate the connection?

Thank you.
jeffez
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Re: Sony Trinitron S-Video Mod

Post by jeffez »

d32xing wrote:Will this work on an NTSC-U unit? I have a similar TV but it's a TS20 like a user stated above. And the red X means eliminate the connection?

Thank you.
I don't see why not. I believe the jungle can operate in both pal and ntsc. And yes the the red crosses mean disconnect. This can be either lifting a component leg or cutting traces. I am also running wires on both sides of the cut so i can switch it back to "stock" rf mode. Since there were composite sets that used the same/similar jungle i think it is possible to do this without the need to cut traces if the jungle can be forced into "composite" mode. This effectively blanks the screen just like done in rgb mods. I haven't been able to figure this out though..
jeffez
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Re: Sony Trinitron S-Video Mod

Post by jeffez »

Updated diagram with Audio added.

This pretty much completes the mod. There may be different/better ways to do this but this is what i can verify as working. This mod requires traces being disconnected and a switch if you want to run the tv in stock rf mode. Next I am looking into if it is possible to do a way simpler switch-less mod with no need to disconnected traces.

Image
jeffez
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by jeffez »

I finally figured out how to do this mod completely switchless. By lifting a grounded pin on the OSD chip, the TV can now go into 'Video' mode using the remote. Video mode originally came disabled on this since it's an rf only set. The pin outputs 5V when in AV mode so i was able to use this to control a switching circuit that toggles between svideo/composite and stock tv mode from the tvs remote.
It's a mess of breadboards and wiring but once all back together it won't even look like a modded tv since there's no external toggle switch or button needed. I know this seems like allot of trouble just to retain the stock tv mode but I started on this 6 months ago and it's become a bit of a passion project just to see how far i could go with it. In future i'll aim to make an updated diagram complete with the switching circuit.
Image
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Bratwurst
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by Bratwurst »

Phenomenal work.

I'm hoping to unlock s-video in a Sharp set that's RF only but I haven't been able to find the schematics unfortunately.
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FinalBaton
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by FinalBaton »

This is so cool, thanks for the work. It'll save many sets from the dump hopefully

I see KV-20HFR/27HRF regularly around here, those look like solid sets but have no S-video.
-FM Synth & Black Metal-
jeffez
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by jeffez »

Bratwurst wrote:Phenomenal work.

I'm hoping to unlock s-video in a Sharp set that's RF only but I haven't been able to find the schematics unfortunately.
FinalBaton wrote:This is so cool, thanks for the work. It'll save many sets from the dump hopefully

I see KV-20HFR/27HRF regularly around here, those look like solid sets but have no S-video.
Thanks guys. Even a really old set with no OSD or unlockable video mode could use this and just have a SPST switch.
Looks like those KV-20HFR/27HRF sets have composite which would make things allot easier.
BWF
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by BWF »

I hope someone here can help me, ive been reading about modding these CRTs now for several weeks but i feel like im chasing my tail. Its clear that there is some fundamental gap in my understanding but i cant seem to get past it.

It seems to me someone should be able to use the data sheet for a jungle IC to plan the circuit modifications necessary to make these mods work without a bunch of trial and error. But so far i havent been able to grasp this. I keep hearing about 75 ohm resistors and .7 Vpp signals but....why do i never see these in actual circuit diagrams for sets, on data sheets, or never measure them anywhere? Ive started measuring Vp-p on input pins with an oscilloscope and recording these on live sets, and the values i see never match what the spec for the jungle says its supposed to be, nor does it match what the "standard" voltage should be. For example, the data sheet for the CXA1870S (for a KV20S20 set) specifies a "standard input level" of 2Vp-p on the YIN pin. Isnt that supposed to be 0.7V p-p? And when i measure it with a scope, why is it nowhere close to either of these voltages (closer to a 1 Vp-p signal sitting on a 3VDC bias). So here i am with a standard that doesnt match the data sheet which doesnt match the measurement. Really frustrating.

Obviously the problem is with my grasp of the concept or lack of skill reading data sheets. Where do i go from here?

It would be easy for me to just copy a circuit from here and move on....but that would be incredibly unsatisfying.

I wanted to post some pictures of the scope measurements and data sheet sheets but I cant figure out how to do that on this forum either. Feeling dumb...help.
jeffez
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by jeffez »

BWF wrote: It seems to me someone should be able to use the data sheet for a jungle IC to plan the circuit modifications necessary to make these mods work without a bunch of trial and error. But so far i havent been able to grasp this.
I started out wanting to do it this way but ended up with the trial and error method as i was also getting nowhere with it. The datasheet for my sets jungle also had odd voltages stated but in the end the thing that worked was just sending the signal straight to the chip with a coupling capacitor and termination resistor shown in the diagram. I have seen newer sets specifically mention 0.7Vpp in the datasheets on rgb lines, so it does happen.
BWF wrote: I wanted to post some pictures of the scope measurements and data sheet sheets but I cant figure out how to do that on this forum either. Feeling dumb...help.
You would need to upload them to an image hosting platform and then put a link to it in an [Img] tag in your post. I use https://imgur.com/ but there are many others.
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Osirus
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by Osirus »

Trying this with my Panasonic after being unsuccessful with RGB. In my Jungle V Sync is the same pin as Y In: https://html.alldatasheet.com/html-pdf/ ... 5165K.html

I 75 ohm terminated both Y and C on my S-video connector and ran them to Y In (39) and C In (43) with 0.1uF caps to the jungle. This had a picture with no sync which was to be expected. I then connected Y on the S video directly to the composite in on the chassis, this got a stable image but it was distorted:
Spoiler
Image
Then I removed the 0.1uF cap between S video Y and composite in, I got a correct, stable image:
Spoiler
Image
But it's blurry, notice the white bleeding in "GAMECUBE". This looks worse than normal Composite In.

Any suggestions? I can't quite duplicate the circuit jeffez posted since I have V-sync and Y on the same pin.
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cyborc
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by cyborc »

Osirus wrote:Trying this with my Panasonic after being unsuccessful with RGB. In my Jungle V Sync is the same pin as Y In: https://html.alldatasheet.com/html-pdf/ ... 5165K.html

I 75 ohm terminated both Y and C on my S-video connector and ran them to Y In (39) and C In (43) with 0.1uF caps to the jungle. This had a picture with no sync which was to be expected. I then connected Y on the S video directly to the composite in on the chassis, this got a stable image but it was distorted:

Then I removed the 0.1uF cap between S video Y and composite in, I got a correct, stable image:

But it's blurry, notice the white bleeding in "GAMECUBE". This looks worse than normal Composite In.

Any suggestions? I can't quite duplicate the circuit jeffez posted since I have V-sync and Y on the same pin.
It might be the composite input's comb filter mucking with the image.
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mikejmoffitt
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by mikejmoffitt »

I had okay results on an old Trinitron that was Composite only, by injecting Chroma into the jungle chip, but just passing Luma in through the composite input. I guess the viability of that will depend on how strongly filtered the Composite input is in order to remove the subcarrier.
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by jeffez »

mikejmoffitt wrote:I had okay results on an old Trinitron that was Composite only, by injecting Chroma into the jungle chip, but just passing Luma in through the composite input. I guess the viability of that will depend on how strongly filtered the Composite input is in order to remove the subcarrier.
This is basically what i was thinking to do on my other larger set seen in my OP which has composite. Things would sure be allot simpler having composite already... The diagram i posted really probably is best suited to RF only sets.
jeffez
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by jeffez »

I have been a bit distracted with other projects lately but just to update i have done up a pcb in cad that contains all the circuitry for the switchless setup i mentioned further up. I found it was going to be too much hassle to do it using a prototype board so i went with this way. I just need to send it off for fabrication now.

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BazookaBen
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by BazookaBen »

Interesting. That might be useful to the KV-13fm12 I'm trying to mod
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BazookaBen
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by BazookaBen »

Jefferz, am I reading your schematic right in that Luma ends up being fed into both Y and C on the jungle chip? I see it being mixed with the Chroma signal after a 470pf capacitor.

Wouldn't that end up essentially turning it into composite video?
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by jeffez »

BazookaBen wrote:Jefferz, am I reading your schematic right in that Luma ends up being fed into both Y and C on the jungle chip? I see it being mixed with the Chroma signal after a 470pf capacitor.

Wouldn't that end up essentially turning it into composite video?
That's a really good point and i think you are right. I added the composite as an after thought. I couldn't see any apparent differences after but that's subjective and i wasn't really looking or expecting anything different with picture quality. Now that you have pointed that out i think it's probably better to remove the composite or come up with a circuit that isolates it. It's really is only a convenience thing i added anyway as you can always get a cheap composite to svideo adaptor.
sergio park
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by sergio park »

Hi Jeffez, I wanna do the same as you did it. Have got a Sony Trinitron KV-21XTR2 that has only composite input, and want to add s-video. Can you help me?
jeffez
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by jeffez »

sergio park wrote:Hi Jeffez, I wanna do the same as you did it. Have got a Sony Trinitron KV-21XTR2 that has only composite input, and want to add s-video. Can you help me?
If you have composite already then things are allot easier. See mikejmoffitts post above. If that doesn't work you could connect the C an Y to the jungle the same way i did then run luma through a sync separator before connecting it your composite line. No need to cut traces like i did either. This is all my best guess though as i dont know what jungle your set has. I couldn't find the service Manuel for it without paying money. I'm guessing you have ruled out rgb modding as an option?
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BazookaBen
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by BazookaBen »

So I'm wondering if I could feed s-video into the second unused set of Y/C inputs on my jungle chip, then use the ID codes in the service menu to trick my TV into thinking it's a larger 20" model with s-video input.

Old post here describing what some of the ID numbers do: https://www.avsforum.com/threads/servic ... st-1714224

Perhaps I could just switch the ID code that decides which inputs to look for? I don't know what side effects changing these codes might have.

I have the 13FM12 with only two composite inputs, and I found that the 20FV12 uses the same micro controller and jungle chip, and has s-video on the back

On 20" TV, Y and C are basically going straight to the jungle, but Y also needs to be fed into a H-sync separator, which then feeds into the microcontroller. I've circled where Y is fed from the s-video input into a video switch, where it is then fed to the sync separator:
Spoiler
Image
Here is the same area on the 13", I think I could simply use a manual switch and add Luma somewhere in this region, around where the video switch is on the 20" model?
Spoiler
Image
Of course, I could try buying that switch chip instead of using a manual switch, because you can see at the bottom on the microcontroller, the switching signal pin could be reconnected. I imagine this pin might become active once I switch my 13" to the 20" model via the ID codes in the service menu. But wiring up that chip could lead to unespected headaches
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by jeffez »

BazookaBen wrote:So I'm wondering if I could feed s-video into the second unused set of Y/C inputs on my jungle chip, then use the ID codes in the service menu to trick my TV into thinking it's a larger 20" model with s-video input.

Old post here describing what some of the ID numbers do: https://www.avsforum.com/threads/servic ... st-1714224

Perhaps I could just switch the ID code that decides which inputs to look for? I don't know what side effects changing these codes might have.

I have the 13FM12 with only two composite inputs, and I found that the 20FV12 uses the same micro controller and jungle chip, and has s-video on the back

On 20" TV, Y and C are basically going straight to the jungle, but Y also needs to be fed into a H-sync separator, which then feeds into the microcontroller. I've circled where Y is fed from the s-video input into a video switch, where it is then fed to the sync separator:
Spoiler
Image
Here is the same area on the 13", I think I could simply use a manual switch and add Luma somewhere in this region, around where the video switch is on the 20" model?
Spoiler
Image
Of course, I could try buying that switch chip instead of using a manual switch, because you can see at the bottom on the microcontroller, the switching signal pin could be reconnected. I imagine this pin might become active once I switch my 13" to the 20" model via the ID codes in the service menu. But wiring up that chip could lead to unespected headaches
I haven't done anything around service codes so i am unsure if/how getting the jungle to use the spare Y/C lines is possible that way. One of the experienced guys on here could probably give you a proper answer on that. I would look into it but failing that i would try the signal pin you mentioned.

I looked up your set and it looks like it's also got RGB input pins on the jungle? Have you looked into rgb modding it? Or is your issue more about how to get the jungle to select the unused input lines? I can see it also has spare unused RGB input pins.
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BazookaBen
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by BazookaBen »

There is a training manual for this series of TV's that I should have read first. It explains everything in three paragraphs that I spent three hours this morning figuring out on the schematic:

EDIT: Actually no it didn't, because I wasn't paying attention to the IC numbers, but it still might be useful to somebody so I'll leave it spoilered
Spoiler
Overview
The following section will discuss the video path for 24” and under BA-5
chassis models. These models have two sets of video inputs and a tuner
input. The rear jack may also have an S Video input. These signals are
routed through the video switch to the YCJ, then to the Comb Filter if
necessary, back through the YCJ, and then output as RGB.

Switching
The composite video signals from the rear jack J201, the front jack J202
and the tuner are all input to IC1304 Video Switch. IC1304 has two inputs
that are used to control the switching. These inputs are V0 and V1 at
IC1304/2 and 4. The input to these pins comes from IC1001 Control
Tuning System at pins 10 and 11. The following table shows the voltage
level at these pins for different input selections:

R= &Input IC1304/2 V0 &IC1304/4 V1 R=Tuner &0 Volts &0 Volts R=Video 1 &3.3 Volts &0 Volts R=Video 2 &0 Volts &3.3 Volts


Whichever input is selected will be output from IC1304/7 and then input to
IC1301/41.
The separate Y and C signals from the S video jack are input directly to
IC1301/2 and 4. If the input chosen is composite video, that signal will be
switched through the YCJ and output at pin 6. Pin 6 is the monitor out line
and would have the Y signal present at its output if an S video source
were chosen. This signal will be used by IC1001 Control Tuning System
for V Chip and Closed Captioning, and by IC1302 Digital Comb Filter.

Digital Comb Filter
The Digital Comb Filter is used when composite video inputs are used.
The composite video signal output at IC1301/6 is buffered and filtered by
Q1311, Q1312, FL1301 and Q1310. You should note that the chroma
signal has a very low amplitude at FL1303. The signal is then input to
IC1302/14 A In. There is also a 3.58 MHz clock signal output at IC1301/
43 FSC and input to IC1302/13. This signal is used by IC1302 Digital
Comb Filter for timing. The Digital Comb Filter has separate Y and C
outputs at pins 20 and 17, respectively. These signals are both buffered
and filtered before being re-input to IC1301 at pins 9 and 7.

Y/C Processing
The YCJ selects which Y and C signal to use for processing. If S video is
selected then the inputs at pins 2 and 4 are used. If composite video is
selected, the inputs at pin 7 and 9 are chosen. Whichever input is chosen, the Y and C signals will be used to create the RGB outputs of IC1301.
These signals will eventually be sent to the tube cathodes.
The YCJ also contains an input for IK to control AKB. The YCJ samples
this signal and determines if each color’s cathode is drawing adequate
current. If the YCJ determines that there is a problem with the IK loop,
video will be blanked. IC1301 YCJ communicates this to IC1001 Control
Tuning System through the I²C bus. This IC will then flash the Standby/
Timer LED in sequences of five to indicate an IK problem.
I'm still not sure if I want to do an RGB mod. I don't think this CRT is high enough resolution to notice any difference between s-video and RGB. I was surpised at how good composite from a Genesis looked.
Last edited by BazookaBen on Sat Feb 20, 2021 2:59 am, edited 1 time in total.
jeffez
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by jeffez »

BazookaBen wrote:There is a training manual for this series of TV's that I should have read first. It explains everything in three paragraphs that I spent three hours this morning figuring out on the schematic:
Overview
The following section will discuss the video path for 24” and under BA-5
chassis models. These models have two sets of video inputs and a tuner
input. The rear jack may also have an S Video input. These signals are
routed through the video switch to the YCJ, then to the Comb Filter if
necessary, back through the YCJ, and then output as RGB.

Switching
The composite video signals from the rear jack J201, the front jack J202
and the tuner are all input to IC1304 Video Switch. IC1304 has two inputs
that are used to control the switching. These inputs are V0 and V1 at
IC1304/2 and 4. The input to these pins comes from IC1001 Control
Tuning System at pins 10 and 11. The following table shows the voltage
level at these pins for different input selections:

R= &Input IC1304/2 V0 &IC1304/4 V1 R=Tuner &0 Volts &0 Volts R=Video 1 &3.3 Volts &0 Volts R=Video 2 &0 Volts &3.3 Volts


Whichever input is selected will be output from IC1304/7 and then input to
IC1301/41.
The separate Y and C signals from the S video jack are input directly to
IC1301/2 and 4. If the input chosen is composite video, that signal will be
switched through the YCJ and output at pin 6. Pin 6 is the monitor out line
and would have the Y signal present at its output if an S video source
were chosen. This signal will be used by IC1001 Control Tuning System
for V Chip and Closed Captioning, and by IC1302 Digital Comb Filter.

Digital Comb Filter
The Digital Comb Filter is used when composite video inputs are used.
The composite video signal output at IC1301/6 is buffered and filtered by
Q1311, Q1312, FL1301 and Q1310. You should note that the chroma
signal has a very low amplitude at FL1303. The signal is then input to
IC1302/14 A In. There is also a 3.58 MHz clock signal output at IC1301/
43 FSC and input to IC1302/13. This signal is used by IC1302 Digital
Comb Filter for timing. The Digital Comb Filter has separate Y and C
outputs at pins 20 and 17, respectively. These signals are both buffered
and filtered before being re-input to IC1301 at pins 9 and 7.

Y/C Processing
The YCJ selects which Y and C signal to use for processing. If S video is
selected then the inputs at pins 2 and 4 are used. If composite video is
selected, the inputs at pin 7 and 9 are chosen. Whichever input is chosen, the Y and C signals will be used to create the RGB outputs of IC1301.
These signals will eventually be sent to the tube cathodes.
The YCJ also contains an input for IK to control AKB. The YCJ samples
this signal and determines if each color’s cathode is drawing adequate
current. If the YCJ determines that there is a problem with the IK loop,
video will be blanked. IC1301 YCJ communicates this to IC1001 Control
Tuning System through the I²C bus. This IC will then flash the Standby/
Timer LED in sequences of five to indicate an IK problem.
I'm still not sure if I want to do an RGB mod. I don't think this CRT is high enough resolution to notice any difference between s-video and RGB. I was surpised at how good composite from a Genesis looked.
That's looks very handy. Let me know how it goes. Sounds like just go with which ever is going to be easier for you (RGB or S-Video). I think s-video holds up well despite RGB having the edge.
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BazookaBen
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by BazookaBen »

I DID IT!

Image
Image
The blur is from my phone camera
Image

I basically copied the schematic for the KV-20KV12 to build the s-video path for the KV-13FM12. They use the exact same boards, so I just had to add in the missing caps and resistors, one IC, and remove a jumper.

But yeah, the picture is amazing on this tube. Totally a worthy set if you're limited on space. Very clean image with fairly linear response from dark to bright, and they're surprisingly sharp for 240p content.

EDIT: had an issue with luma but it was my fault, did a poor job soldering termination resistor.
Last edited by BazookaBen on Mon Feb 22, 2021 3:20 am, edited 1 time in total.
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matt
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by matt »

For what it's worth, I was able to add S-Video to a KV-20S90 (BA-4D chassis) a few days ago. It should work with other 13" and 20" BA-4/4D TVs. The schematic is slightly different from the BA-5 models, but it's similar enough that some of what I did may be relevant.

Sorry, no pics - I didn't think to take any and have since removed the mod since I don't have an immediate use for it.

Luma goes through the rear A/V jack (on the BA-4D, Luma and Video 1 both go to pin 4 of the Jungle IC). Chroma goes to pin 2, with a 75ohm terminating resistor and a 0.01uf coupling capacitor.

By itself, this doesn't do anything - the chroma input is disabled and the picture will still be black & white. Fortunately, this can be changed in the service menu. The A/V input setting are governed by ID-1, which has a default value of 3 on my TV. To enable S-Video, add 16 to whatever its initial value was (in this case, it should be changed to 19). The ID bits appear to be the same on BA-5 models.

Now the picture will be in color, but very blurry since it's running the video through the luma trap filter. Disable CTRP in the service menu to clean it up. This means that composite will now look terrible, so you'll have to go back to the service menu every time you want to switch between composite and Y/C.

I was pleasantly surprised with how good the picture was with this mod. It's incredibly crisp and just a hair below RGB.
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by jeffez »

BazookaBen wrote:I DID IT!

Image
Image
The blur is from my phone camera
Image

I basically copied the schematic for the KV-20KV12 to build the s-video path for the KV-13FM12. They use the exact same boards, so I just had to add in the missing caps and resistors, one IC, and remove a jumper.

But yeah, the picture is amazing on this tube. Totally a worthy set if you're limited on space. Very clean image with fairly linear response from dark to bright, and they're surprisingly sharp for 240p content.

EDIT: had an issue with luma but it was my fault, did a poor job soldering termination resistor.
Good stuff! Looks great! My pcb design didn't work despite the same circuit working on the breadboard so i must have messed something up. Bit of a shame as it took me allot of time. Will have something to show sooner or later, just need the time.
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BrianC
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by BrianC »

Neat stuff. I have a Toshiba TV with only A/V inputs that looks like it has a place where s-video should go. Would this be possible to mod? It also has a VCR and DVD built in.
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BazookaBen
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by BazookaBen »

BrianC wrote:Neat stuff. I have a Toshiba TV with only A/V inputs that looks like it has a place where s-video should go. Would this be possible to mod? It also has a VCR and DVD built in.
Are there larger toshibas with the same chassis that have s-video? Same or similar jungle chip? Just copy the circuit.

If you can find the appropriate service manuals I can take a look
deeplistened
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by deeplistened »

BazookaBen wrote:I DID IT!

Image
Image
The blur is from my phone camera
Image

I basically copied the schematic for the KV-20KV12 to build the s-video path for the KV-13FM12. They use the exact same boards, so I just had to add in the missing caps and resistors, one IC, and remove a jumper.

But yeah, the picture is amazing on this tube. Totally a worthy set if you're limited on space. Very clean image with fairly linear response from dark to bright, and they're surprisingly sharp for 240p content.

EDIT: had an issue with luma but it was my fault, did a poor job soldering termination resistor.
I have this exact same set! I've been digging in the RGB mod thread, but an S-Video mod seems much easier and feasible for a screen this size. Would you mind posting a short guide of what you did exactly? Or at least the values of your caps/resistors, what IC you used, and the number of the jumper you removed? Thanks!
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BazookaBen
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Re: Sony Trinitron S-Video/Composite Mod (RF-only TV)

Post by BazookaBen »

deeplistened wrote:Would you mind posting a short guide of what you did exactly?
Yeah thanks for reminding me. Let me know when you finish it so I know it worked out


First off, you're really just dealing with Y and C. All the traces are already going where they need to go, because this is the same board used in the 20" and 24" models, so you just need to fill in the missing components.

C goes to the jungle, while Y goes to both the tuning control processor and the jungle chip.

Constantly check continuity to make sure you're following the signals correctly

Most of the mod takes place on the MB board, but you will start on the A board.

On the A board:

The insertion points for Y, C, and grounds are all right behind the composite connector in a row. Careful here, I damaged one of the pads and had to jump in elsewhere.

Next, if you check continuity you find that Y and C will need wire jumpers under the RF tuner. I was able to feed some jumpers in with tweezers, but you could also temporarily remove the RF tuner, or just not use the jumpers at all and just run wires directly to this point form the s-video connector.

From there, the circuit is complete to the MB board connectors.

On the MB board:

Add 10uf electrolytic cap at c1002, and then add the video switching chip at location ic1002. Make sure you check the service manual, datasheet, and check continuity to make sure you're matching pin 1 to the right pad

This IC basically switches between composite and luma inputs, which is then is stripped down to H-sync, which then feeds to the tuning control processor. Why the tuning control processor needs access to H-sync, I'm not sure. Maybe it's to line up the OSD properly

Anyway, this chip is listed as NJM2534M(TE2) in the manual, I found NJM2534M-ND at digikey and it works fine: https://www.digikey.com/en/products/det ... 34M/638835

So now that you have this chip feeding the appropriate signal, you need to remove the SMD jumper, JR1083, that used to carry the composite signal directly to the tuning control chip.

Now all that's left is to add the components needed for properly terminated Y and C going to the jungle.

r1318 and r1317 are 75ohm resistors for terminating Y and C to ground, they're supposed to be SMD but I just used tiny 1/8th watt through-hole style resistors.

C1389 is a non-polar 0.1uf cap on the C line, supposed to be SMD, but I used a tiny film cap.

C1367 is another 10uf electrolytic cap on the Y line

And that's it on the hardware side!

In the service menu:

Now the last thing you need to is go into the service menu and change ID-1 from 3 to 19. This unlocks the s-video input.

Video 1 will now be both the rear composite and the s-video input, depending on which you have plugged in. Not sure what happens if you have both plugged in.

TLDR:
  • Default solder spots for Y, C, and grounds are right behind composite connector

    Add jumpers for Y and C on A board.

    Add ic1002, c1002, c1367, c1389, r1317, and r1318 on the MB board.

    remove JR1083 on MB board

    change ID-1 to 19 in service menu


here's the relevant manuals and datasheets, with my parts list, copied from the 20FV12 service manual:

https://drive.google.com/drive/folders/ ... sp=sharing



Here's my finished MB board, the two 10uf electrolytics are on the opposite side:
Spoiler
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One last side note: I expected r1412 to be missing, because it is present on the switching signal from the tuning control chip to the video switch chip on the 20FV12, but isn't listed in the manual for the 13fm12. But on my board it's present. I already had a complete signal between the two chips. I imagine it is on yours as well, but if you have issues, you could double check.
Last edited by BazookaBen on Fri Mar 26, 2021 3:44 am, edited 1 time in total.
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