Topic: C128 80 clumn RGB to S-Video...

[Mangelore]

Hi guys,

Apologies for not posting here that often lately.
Struggling to find free time at the moment.

Anyway, I scored an affordable RGB to S-video converter and was curious to see how it performed on my Sony TV.
Surprisingly, the quality was much better than expected :-)

Time to get all 16 colours working on it.

Cheers
Fotios

[redrumloa]

Nice!!! Need, more info..

You have been a treasure to the C= community :-)

[gklinger]

I think of him more as a superhero. You know, with FB superimposed on a lightning bolt on his chest.

Jokes aside, this is of more interest to me than an RBG to VGA adaptor because all the displays in my house have S-video inputs and the quality is quite good. It's also worth noting that the 128 can display 80 columns nicely through an S-video connection although it's only monochrome.

[Hydrophilic]

If you're planning on making and selling these then I can't wait!  If not, details please!  Golan is right; I have my Commie connnected to a 36-inch (1m) TV and it looks sharp in both 40 and 80 column, but monochrome is so boring (and impossible to use with some apps).

[Mangelore]

No need to thank me. Thank the guys in Taiwan who make this stuff :-)
I'm using the following converter
http://www.weiya.com.tw/products_1.asp?le=english&fid=114

Seems to work fine on my TV with an Amiga as well.

My TV is a 5+ year old Sony that has a mode called Game Mode. When active, it's like a flicker fixer that gets rid of the interlaced effect in 640x512 mode. After all this time I finally figured out what this mode was for... the description in the Sony user guide was crap.

The image is better than the photos shown due to my crap photography skills.

I don't have any plans to resell these... However, I'll try to source some from the manufacturer at wholesale prices.

I wonder how it will perform on a S-Video to VGA converter... there's so many around. Any recommendations?

Cheers
Fotios

[airship]

Is the 16-color conversion the same as for the VGA converter? 3 resistors?

[Mangelore]

Not sure. I need to spend some time reverse engineering it but I'm keeping my fingers crossed that a few diodes and resistors will once again do the trick.

[Hydrophilic]

Thanks for the link.  It's a shame it needs 12V instead of 5V, but if it doesn't draw too much current, it should be possible to convert the 9VAC out of the user port (conviently located by the RGBI port).

The large view of the board marks the output as composite, but you said you were using S-Video.  So did you just tap the Luma / Croma lines before the composite stage?

[Mangelore]

I'm thinking of using it with a 128D that has +12V.

The S-video socket is between the power and composite sockets.

[airship]

How much regulated 12V current comes off the 7812 (U59) regulator in a flat C128? It's pumping 12V for the 6581 SID, but I don't know the circuit's capacity. Looks to me like the caps and diodes should handle some extra load, and the 7812 should be okay with it. The output's got a 10 uf cap on it, so I can't believe it would affect the SID much. There's no outside connection, but you should be able to clip onto it with a pigtail pretty easily.

[Mangelore]

Well, the video converter circuit spec sheet states that a 125mA +12V supply will do the job.

[Hydrophilic]

How much regulated 12V current comes off the 7812 (U59) regulator in a flat C128?

I don't know because the 7812 is a very common component made by several companies in a wide range of current ratings.  It wouldn't suprise me if Commodore used several types in the different production runs.  Anyway, a quick google shows ratings from 500mA to over 2000mA, so I think whatever 7812 was used should be OK.

But, the circuit is fed by the 9V AC.  The 9V output on the user port is spec'd at 100mA.  So this neat device may draw too much current...  It really depends on how much 9V current the power brick supplies.  The markings on my power supply specifies ~1000mA.  Since the C128 PRG states the worst-case consumption is 5.2W of 9V = 577mA,  over 400mA should still be available from the power brick, so it may work after all!

Now I'm even more curious about this device.  Is there a way I can buy 1 (and not 50+) ?

[Mangelore]

Now I'm even more curious about this device.  Is there a way I can buy 1 (and not 50+) ?

This eBayer seems to list them from time to time.
http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&rd=1&item=310046061559

[Hydrophilic]

Thanks Mangelore!!

(duh, eBay... hydro slaps forehead with palm)

And very reasonably priced.  Excuse me while I do some accounting...

Edit
I just noticed the item is located in Canada.  It should get here by Christmas right?
/Edit

[airship]

Let's not start THAT discussion again! Last time we started in on Canada Post we lost a half dozen good members!

[stevevb]

I am working on something similar to this device based on  the AD72X series ( Probably AD724...should get my sample soon, just waiting to get an oscilloscope )

http://www.analog.com/en/prod/0,,765_798_AD724,00.html

[Mangelore]

Cool!

Just so you know, the device I'm using is based on the BH7236AF
http://www.datasheetcatalog.com/datasheets_pdf/B/H/7/2/BH7236AF.shtml

[Hydrophilic]

I just got my RGB to S-Video/Composite converter and it works very nice... thanks again Mangelore!!  I ordered from the guy Mangelore mentioned.  It was $25 + $13 shipping.  Shipping took about a week but I'm not gonna blame the seller, all things considered.

The converter also came with: Composite, S-Video, and DC Jack cables.  Note it does not come with 12V DC adapter.  Also included was a specification sheet.  It says (amongst other things) that it operates on 8 to 15 V DC.

To test it, I went to RadioShack and bought a 9-pin male D-sub connector, matching housing, and a pack of 9V battery clips.  About $8 with tax.  The one thing I really needed I could not find: a post connector :mad:  The device has two post connectors.  One is 'large' with all input signals except V-Sync.  The small one has all input signals.  Since they didn't have any post connectors :mad:, I used some in-line crimp connectors.  Needless to say the video-in wiring looks really bad...

After hooking up the device I powered it on and ... nothing!  After double checking my wiring and testing that Ground, RGB, H-Sync and V-Sync signals were reaching the device, I thought maybe 9V wasn't enough (or maybe the battery I was testing with was too old).  So I cracked open a 1571 and borrowed its power supply.  Connected 12V, powered it up and ... nothing!

I was getting worried at that point.  I verified the power connection.  Yep, 13.3V on the DC plug and the Positive was connected to the pin labeled +12V on the circuit board.

Then I remember the photo the seller had posted about how to connect the DC plug's wires... they were backwards from what I was using.  I used a multi-meter and discovered the connector on the board labeled +12V was actually common to the ground.  And the pin labeld CON only went to a diode which was reverse-biased with the polarity I was trying to use.

So I switched the polarity that the 1571 supply was feeding the device and... success!  A color 80-column display

Next I set aside the 1571 and re-attached the 9V battery (with the right polarity).  I turned it on and... success

At this point I was using the Composite output because the front of my TV only has composite video in.  I was worried because the image was very blurry.  (Previously I was using composite with the 128's monochrome output and it gave a very sharp picture).

So I crossed my fingers, climbed behind the TV to connect the S-Video cable, turned it on and... success: A colorful and sharp 80-Column display

Obviously I'm biased, but the Color S-Video looks as sharp as the monochrome composite.  And it looks better, not just because of color, but because of brightness.  With monochrome, the output was too bright with the standard TV settings (I would change from bright cyan to a dark color like blue to get a slightly dimmer but still 'white' text display).  But with the Color S-Video, the brightness is perfect.  The device comes with 3 pots to adjust R, B, and G signals but I didn't need to touch them.

If you have C128 and no 80-column monitor, I recommend this if:
1) You have TV with S-Video input
or
2) You have a good 40-column monitor -- meaning one with seperate chroma and luma inputs like the 1702 because seperate luma/chroma is exactly what S-Video is... Commodore was ahead of the home entertainment industry
and
3) You have a nack for simple electronic projects

Important point to remember: the DC Plug should be wired with a positive tip and a negative barrell (ignore the +12V marking on the board).

Next I'm gonna dig around for some diodes and resistors and see what I can do about intensity.  I'll also use some diodes to build a bridge rectifier and put a big capacitor on it, then test it with 9VAC.  I should probably get a case to hide my ugly wiring

[gklinger]

What about the CGA colour issue?

[Hydrophilic]

The device does a straight RGB conversion so there is no color issue with a television.  There shouldn't be any problem with a Commodore monitor (like 1702).  The only problem, I guess, would be if you tried to use an IBM/CGA  monitor -- but I don't have one so I can't be sure...

[gklinger]

D'oh. I didn't occur to me that the problems associated with a 128 to VGA adaptor wouldn't be present with this device. Sounds like I'll have to get one. Anything to be rid of the need for monitors.

[klx300r]

No need to thank me. Thank the guys in Taiwan who make this stuff :-)
I'm using the following converter
http://www.weiya.com.tw/products_1.asp?le=english&fid=114

Seems to work fine on my TV with an Amiga as well.

My TV is a 5+ year old Sony that has a mode called Game Mode. When active, it's like a flicker fixer that gets rid of the interlaced effect in 640x512 mode. After all this time I finally figured out what this mode was for... the description in the Sony user guide was crap.

wow..glad i checked in to this site....youre telling me that this thing is actually good for AGA games as well i.e no colour loss?

[got128]

Does anyone know of another supplier for this converter?  I checked the ebay site listed, but he's not selling right now.  I have contacted the manufacturer, but i have not gotten a response as of yet.

I had a thomson monitor , but it smoked - quite literally!!

thanks 
got128

[airship]

Bumping this thread...

Mangelore, Hydrophilic, did you ever get Intensity wired up? Did it work?

Has anyone found another (preferably US) supplier?

[Hydrophilic]

No I haven't got the intensity or the power-via-C128 wired up.  My f*** car has been taking away from my precious Commodore time   Its on my todo list so I'll post eventually.

As long as I'm posting I just want to make some comments about this tiny device.

It does RGB conversion so you only get 8 colors and not all 16.  For all 16 colors you need the intensity circuit we're talking about.  An ASCII schematic for you:

Code: [Select]

    +----/\/\/\/---->|---- R
    |
I --+----/\/\/\/---->|---- G
    |
    +----/\/\/\/---->|---- B
where the resistors are around 680 ohms.  The normal R,G,B lines from the C128 would also connect to R,G,B above.  Here's a picture of one soldered directly to a converter board.  Not how I'd do it... I don't trust my soldering skills on this device -- lots of surface mount components!

Also let me say this device has two post connectors.  A large, 5-post connector which supports composite-sync RGB input, and a small, 6-post connector which supports seperate(H and V)-sync RGB input.  The C128's VDC produces seperate H,V outputs so plan on using the small connector.  You could easily create a composite sync by connecting the H and V with a capacitor but I don't what value to use (in this case use the large connector).

Also the composite-sync on the large connector is wired to H sync on the small connector.  This might be important if for some reason you wanted to use both connectors.  Using both connectors may sound unlikely, but is actually what I did because I didn't have a proper connector; I used wire crimps which fit nicely on the big posts but I still needed the V sync from the small connector.