Can I use this TV for RGB input?

[elkameleon]

Hey guys, I have a sanyo 14" tv that I took apart that I was thinking about using for a small arcade machine. Unfortunately it only has coaxial inputs. I poked around a bit and found some RGB labels on the neckboard, would this be a candidate for hacking in some RGB from my video card using Soft15KHz?


neck board


close up of RGB pins


chassis board


closeup of signal process IC

[boardjunkie]

That would work for the color signals, but you still need to put sync in somewhere. The composite video input works for that. So, while it will work, it may not look the best. You lose all the color adjustment and processing that the "jungle" chip provides. In addition, you'll need a video amplifier for it to even display a usable pix. The .7vac from your video card output ain't hot enough to get correct colors. You need to be up around 3-4vac to be in the ball park.

[MonMotha]

With a little hackery, this is often possible.  What you do is generate CVBS using a little combiner circuit, apply that to the composite input to get the thing to generate all the deflection, then yank the existing RGB lines and apply RGB video to them directly.  As boardjunkie said, a video amp will likely be required.  You will also need to run the set off an isolation transformer, otherwise you'll very likely end up with a ground loop that will damage/destroy your video card and possibly you, too.  I can't find any docs on the LA7673 IC you have pictured (nor can I read any of the others), it's difficult to know much about how this set works.  It might not be the best candidate for this kind of modification.

EDIT: Oh wait, this thing doesn't even have a composite video input.  I wouldn't bother with this thing at all.

[elkameleon]

Oh well I guess, I found the tv in the garage... and it worked, so I'm not really out anything. I too tried to find at least a pinout for that chip, came up empty handed as well.

[lilshawn]

e-mail sanyo and ask for a datasheet for the LM7673. whats to lose?

[elkameleon]

Heh, I guess I could try that

[elkameleon]

I got a response from sanyo support, it was a rather "dont bother us" canned response, but a response nonetheless.

Due to the age of the unit the information requested in no longer available.

Thank you

[elkameleon]

I found a link in one of the many PDFs stating that this IC was discontinued in march of 2010, so I tried emailing the semiconductor division to see if I have better luck. The TV may have been made in 1997, but the part was only discontinued last year, there has to be some details laying around somewhere...

[elkameleon]

I got a response....

Thank you for your inquiry.

Unfortunately I could not get data sheet because of discontinued product. Sanyo doesn't supply it of obsolete ones anyone else except customers who designed products with this IC.

Sorry about that.

Not what I wanted to hear unfortunately.

[lilshawn]

well you can't say you tried. hit the trash bins around town and see what else you can find

[newmanfamilyvlogs]

http://cs.utsource.net/goods_files/pdf/40/40331_SANYO_LA7674.pdf

I wonder how close this one is.

[elkameleon]

I dont know if its a perfect match, but it does have the same amount of pins... I will have to do some testing and see if some of the pins match, you might just be a savior!

[lilshawn]

I would say it's not very likely. I'm thinking that chip was made for that particular television (or series) if your going to toss the TV it couldn't hurt to experiment with it.

[elkameleon]

Yeah, I dont plan on using the TV, so might as well futz with it till it blows up

To be honest, I know my way around electronics, and I can read a schematic, but I wouldn't really know where to begin here with this one... The only place I see RGB in would be at the OSD display...

[lilshawn]

if you could take i high res picture or scan of both sides of the neck card i might be able to figure it out.

[elkameleon]

That can be done, gimme a few mins.

[elkameleon]

The best picture I could get of the solder side of the neck board is already at the top of this post, just right click the image and "open in new tab" to get the full image, i'll work on the component side, but the lighting blows in here...

[elkameleon]

I traced pin 18 (R-Y out) from the IC, it goes to pin one on the cable that goes to the neckboard, which happens to be labelled R... I think this may be a close enough match to get me the correct pins at least. Can I just feed RGB in at these pins? Where would I put sync?

[lilshawn]

oh right, i remember now... i've been following threads on my phone, so i haven't been seeing pics.

your issue is that you would be trying to directly drive the transistors for the guns... not going to happen.

i don't have a pinout of the tuner but i suspect the output of the tuner is composite and is being fed directly to your LA7673. if that's the case the sync will be controlled by the chip as well. (will have a sync output driving the horizontal stage someplace)

if you could source an LM1203 or a LM1204... will get you where you need to be for your video level to drive the transistors... but you still need to drive the sync somehow.

[elkameleon]

Man, I wish I knew more about this kinda stuff... Jealousy ensues.