This tutorial aims to describe how to clone a JVC IF-C01COMG RGB card for JVC monitors. It should also works with Panasonic monitors.
As you may or may not know, some JVC monitors have one or more expansion slots, and the most relevant for retro consoles is the IF-C01COMG (AKA BT-YA702 for Panasonic) as it allows RGB and component video input. It is especially important for DT-V and BT-H line of monitors, as they have 3 slots but no stock input, not even composite.
This card is rare, most of the time you will find these monitors fitted with SDI / HDSDI cards, which are useless for retro purposes. Owners of such cards will also often ride the retro craze to inflate the prices to crazy levels, sometimes more than the monitor itself.
I was lucky to find a monitor with an RGB card. At some point I got curious and opened it and to my surprise it's made with pretty much standard components. Not only that, but a closer look revealed that about 85% of components serve no purpose, as some components are missing in critical places. The card just does some input protection, buffering and level adjustment.
This was confirmed by looking at the schematics I was shown later.
Note that I didn't bother doing the audio part as audio on these monitors are mono and very small. I'll list the parts for it, but you're on your own for it.
I first thought about using a service like OSHPark, but I quickly went against it as the board is very large for what it does and prices are surface-based, and I also have no CAD experience. I then went for a perfborard approach, and I could find decently sized ones, that would at least fit the slot guiding rails. Some wires to a panel will route the signals, also allowing different connector types, such as a SCART socket, RCAs, VGA... I didn't bother with any kind of passthrough, if you want/need that you need to figure it out.
My main concern was the connector used, it's a DIN 41612 style with 50 pins (2x25). 50 pin version isn't actually DIN standard. It's a Hirose PCN10A 50P.
However the pin spacing is standard 2.54mm, so I tried a more cheap and common 50 pin angled box header like those SCSI and it worked fine.
single sided perfboard / prototype board 2.54mm pitch with at least a 128mm length
10µF 50v x2
47µF 25v x4
100µF 16v x2
IDC DC3 50PL connector
1-2mm steel / alu / plastic plate.
Some wires and connector of your choice for the panel, like a JST connector and socket for easy swapping (5 pins for RGB, Sync, ground ; 6 for RGB, HSync, VSync, ground).
AUDIO PARTS (OPTIONAL, NOT COVERED HERE)
1µF 50v x1
Zener 12v x1
First you need to cut your perfboard to the correct height. The original card is around 130mm, I managed to cut it to around 128mm, the difference will help for centering the card when pluging it.
Then you can solder the connector, place it so it's flush (or nearly enough) and make sure it is as centered as possible, file/grind the upper/lower sides of the board to adjust the centering.
Now the tricky part is planning where and how to place components. I highly recommend making a drawing, either on paper (pencil, eraser and graph paper helps tremendously) or on CAD if you're efficient with it. I went with a maximum of 3 legs per hole, for the most part it worked well but be careful as some legs are thicker and forcing a leg in can tear the copper pad (rare but happens). If there are 4 legs to be connected, I just solder the 4th leg on top of another.
This is my drawing, feel free to get inspiration from it, to tweak it.
Note that I went for a very compact plan just in case, but you have quite a bit of space to work with, so you can probably manage some more relaxed placement. As for the traces, the usual way is using one of the uncut leg by bending it flat along the board to make contact to the end, and fill the space with solder ; you can do it with just solder across the pads but it's actually kinda hard without a leg or a bare wire to guide the solder.
You will also need some wires to do some connections, like for the inputs and between outputs and connector.
There's the ground traces to make, as I said, it's much easier to have a bare wire running along and then using it as a guide for solder, than just trying to solder between pads, even more with these lengths.
This is my card finished, I pierced a hole and attached a zip tie so I can pull it out more easily, the single slots being a bit cramped.
I made the panel out of a 1mm steel plate, in the end it was a bit overkill, unless you are equiped for or comfortable working with metal use some plastic or wood instead, heck even some thick cardboard might do the trick. The plate needs to be around 42mm wide and 155mm tall. Depending on your monitor and/or slot you might need to cut top-right and bottom-left corners to make room for some screws.
I salvaged the scart socket out of a cheap multi-scart, connected all the grounds, the signal wires, and routed audio out to a pair of RCAs just in case there's no audio breakout on the cable.
Once everything is done and you've checked everything is wired and soldered correctly with no bridges, you are ready to insert. Slide the card in the guiding rails, once you're at the bottom, lightly wiggle the board up and down to find the right matting between pins and sockets. Only when you're sure they're matted push for securing in. Then fold the wire and tie in, screw your panel and you're ready to test. Remember that for RGBS or RGBHV you need to set your input to external sync, while for RGsB or YpBpR you need internal sync.
Because of guiding rails length, card should be around at least around 42mm long to not fall off rails when inserting/removing.
After some searching, I found that there are some perfboard that are 180x128mm, which is right about the size of the original card, or could be split in 2 for making 2 cards.
There's also some cards on ebay or aliexpress that are 250x130mm, which should be good for up to 3 boards. Searching for "prototype board" yields better results compared to "perfboard" FYI.
You can probably use other NPN transistors like the common 2N3904, but be warry of pinout, C945 being ECB and 3904 is EBC so adapt your circuit accordingly.
The original regulator is a BA12T, it's a low dropout (LDO). You CANNOT use a 7812 because there's not enough difference between in and out (14, 12v). The upside is that LDOs run much cooler and you don't need a heatsink.
Horizontal and vertical sync inputs have 2 150R resistors in parallel for termination, this is equivalent to 75R. I'm guessing they did this for spliting load as the resistors are very tiny. Should be fine for regular sized resistors.
Thanks to Star1 from Shmups forums for providing schematics and parts list, wasn't really needed at this point but provided nice confirmations about circuit.
If you attempt this, good luck ! It's not terribly hard but a bit long and tedious.
If you have ideas, suggestions, corrections, absolutely submit them, I'm on Shmups, Sega-16 forums, this will also be on my Pastebin account so it will be updated if needed. Also in 4chan /vr/ CRT thread.
Finally, please make this document available to as many users as possible. JVC / Panasonic monitors are of exceptional quality, and some pass on them because of lack of RGB capability. This is especially true with DT-V line that. Some card owners are also starting to jackup prices, I've seen a 15" monitor go for 220€ just because it had the RGB card.