Thoughts On Enabling Component Input On A Funai Symphonic CRT TV

[titan91]

I have a cheaper Funai model, branded Symphonic, that has RF and composite inputs from the factory. I opened it up and saw some jumpers labeled YUV-R and YUV-B, and looked at the service manual. While the YPbPr pins on the chip for this model, the WF24T5, are not labeled, I did find them labeled in the service manual for a fancier Symphonic model that has component inputs from the factory (the CST274FE). I entered the service menu and set the available inputs to V1,V2,YUV to make Video 1 and Component selectable as inputs.

I then proceeded with a typical input mod: Removed all factory ground terminations from these lines, added missing jumpers to the traces, added missing 1uf AC coupling capacitors, and terminated each line to ground using 75 ohm resistors. But, nothing shows up when switch to the component input. I also found Y and C input pins for s-video and did the same procedure above for those but I also enabled the s-video switch on pin 61 of the chip by tying that to 5v power rail with a series resistor per the service manual of other Symphonic sets that have factory s-video.

When testing, Video 1 does show s-video per normal, but Component shows a color picture as well. Huh? I then disconnected the C line and saw Video 1 and Component now show a black and white image. So it seems the Component input actually ignores the YUV input pins on the chip and listens to the Y/C pins instead.

Does anyone have detailed experience with the service menu or adding component to a Funai/Symphonic TV? The issue is clearly in software. I'm not sure if that's fixable by adjusting the options, setting the 7F option byte to something other than FF, etc. I pored through the "electrical adjustments" section of the fancy model with factory component inputs and don't see any options that stand out.

Also, there is something off about the s-video input I enabled. It seems a bit too soft at 480i and I see a minor amount of chroma dot crosstalk over the whole picture in areas of strong color. The focus adjustment of the TV is fine because the on-screen menus look crisp and I get good scanlines. It looks fine at 240p. I have a feeling the comb filter that is used in composite mode is applied to s-video inputs as well, softening the Y channel unnecessarily. There is a "filter" adjustment in the service menu but I believe that is just for content filtering and parental control.

[Josh128]

I enabled S-video on a 20" flat tube Symphonic/Funai a couple of years ago. Had to use a switch to enable like you are doing. It works well, but the image shows signal reflection /shadow just to the right of whites and bright colors. I was never able to eliminate it.

[titan91]

Cool, did you test it before adding the s-video enable switch going to pin 61? I assume it would not work without that line pulled high to 5v through this 22k resistor:

Spoiler

Now I'm wondering if that being always on is bypassing the component inputs. Unlikely...

[Josh128]

I have a switch that applies the +5V to enable it, without it applied, it doesnt work.

[titan91]

I looked at this block diagram but am not seeing anything to indicate why the component inputs wouldn't work. There is a different 4-digit preset code in the power left of the screen, and the manual says that code can be changed. I may try adjusting that to reflect the code shown on the component/s-video factory model. If I break something at least there is a factory reset option in the menu and a jumper on the board itself called "short factory."

Spoiler

[vol.2]

It works well, but the image shows signal reflection /shadow just to the right of whites and bright colors. I was never able to eliminate it.

This seems to be an issue that can present itself when hacking in other inputs. I've seen visible ringing and reflections in 2 separate projects I did. One was an OSD RGB hack on a Toshiba, and the other more recently I'm seeing some ringing in an s-video mod I did to a small Sony TV.

I'm wondering if it maybe I could solve it by swapping the wires I used for something shielded, or possibly it might need a different capacitor value on the chroma input or something?

[titan91]

Ah nope... I messed up and overlooked the fact that the actual pins between the chip in mine and that component model are different. Those pins don't handle video on the chip in my WF24T5. They are used for sound:

Spoiler

Here's the same area of the schematic for the CST274FE model with component:

Spoiler

Here's what I THOUGHT I was looking at, which is wrong for my TV:

Spoiler

Part of the issue is my service manual is a supplement with the schematic only, not the IC pin functions list. So it's a little harder to follow.

So that's a waste of time, it seems... oh well, mystery solved. Why mark these jumpers on the board then and make me spend 2 hours tracking everything down? I seriously hate these Funai board designs.

[lynx8639a]

I have a switch that applies the +5V to enable it, without it applied, it doesnt work.

I've been looking to s-video mod this same TV and have a few questions. Did you just directly hook up pins 29 and 30 to the s video connector and run 5v to pin 61 or did you need to add resistors to the Y/C lines?

[Josh128]

I have a switch that applies the +5V to enable it, without it applied, it doesnt work.

I've been looking to s-video mod this same TV and have a few questions. Did you just directly hook up pins 29 and 30 to the s video connector and run 5v to pin 61 or did you need to add resistors to the Y/C lines?

I did hook them up both directly and with resistors in an attempt to negate what I can only describe as signal reflections that appear as shadows just to the right of imagery. Even though the S-Video was crystal clear , I was not able to get rid of the reflections, despite trying different resistors parallel to ground and/or in series with both Y and C. I think the reflections are from impedance mismatching. I'll see if I can crack open the set to see its current configuration, but if you happen upon a fix for yours, please post it here.

[lynx8639a]

I have a switch that applies the +5V to enable it, without it applied, it doesnt work.

I've been looking to s-video mod this same TV and have a few questions. Did you just directly hook up pins 29 and 30 to the s video connector and run 5v to pin 61 or did you need to add resistors to the Y/C lines?

I did hook them up both directly and with resistors in an attempt to negate what I can only describe as signal reflections that appear as shadows just to the right of imagery. Even though the S-Video was crystal clear , I was not able to get rid of the reflections, despite trying different resistors parallel to ground and/or in series with both Y and C. I think the reflections are from impedance mismatching. I'll see if I can crack open the set to see its current configuration, but if you happen upon a fix for yours, please post it here.

Thank you for your response! I'll probably crack it open some time this weekend and see if I can tinker with it and come up with something

[lynx8639a]

I have a switch that applies the +5V to enable it, without it applied, it doesnt work.

I've been looking to s-video mod this same TV and have a few questions. Did you just directly hook up pins 29 and 30 to the s video connector and run 5v to pin 61 or did you need to add resistors to the Y/C lines?

I did hook them up both directly and with resistors in an attempt to negate what I can only describe as signal reflections that appear as shadows just to the right of imagery. Even though the S-Video was crystal clear , I was not able to get rid of the reflections, despite trying different resistors parallel to ground and/or in series with both Y and C. I think the reflections are from impedance mismatching. I'll see if I can crack open the set to see its current configuration, but if you happen upon a fix for yours, please post it here.

I have one more question about the 5v to pin 61. Did you run around 5ish volts from somewhere in the tv directly to the pin on the IC or did you run it through a 22k resistor like in the service manual?

[Josh128]

Probably direct, but I will check. Can you post a pic what you are talking about ie does the service manual contain a how-to on enabling S-video?

[lynx8639a]

I think I was just getting confused between service manuals. I've got the one pulled up that was discussed earlier in the thread (cst274fe) but it looks like that s-sw line doesn't actually go through the 22k resistor, just comes straight out of the s video jack in to pin 61. If you could get some pics of yours while you're inside it would be great, but if not no worries!