Bit of a thread necro as I managed to bag 3 intellivisions offof ebay, plus a speech module, for £38 posted. (SCORE!) :lol:
anyway smalltime bragging over - hooked them up, they all worked, with varying degrees of RF nicety. One actually produced a very nice RF picture after tweaking the pots a little. The other two not so much. They're all the same radofin design as per the OP. I've prodded around the RGB board and found this so far;
intellivision pal vid.jpg
Basically the colour inputs (V1-V4) and control bit (v5) are anded through the 7408 so pixels are drawn when V5 plus a combo of V1-4 are high.
V1-3 are fed to two different 7442 4-bit to 10x1 bit decoders. V4 is sent straight to one decoder and inverted and sent to the other. not all outputs are used but the ones that are correspond to the 15 colours (not including black as 16th) the console uses.
That was far as i got with plotting the schematics but tracing the board shows each colour then being fed through resistors to 3 rails - some colours are fed through an inverter and more resistors to the same rails. I've drawn these lines but not got as far as measuring their resistance. Ideally the 3 rails would be RGB but I'm betting they're not and are processed more, ending up as R-Y G-Y B-Y fed to the TBA520 to produce comp. Anyway I got bored/overwhelmed at this point and went down the composite route.
I already had an intellivision I'd installed a cleancomp universal board on. This works well. But a little pricey for what it is (considering my initial outlay). So I built and installed the same mod as RJ et al. I'm not sure its great for PAL... some pictures cause shearing and even rolling depending on colours used (and this is with tweaking all the pots). I took the modulator out which made the picture nicer and usable with plenty of games that are mostly black background, but colourful games with solid backgrounds looked less pretty, with vertical banding, shearing etc. I then decased the modulator and used the hollowed out casing to put the comp mod PCB in, hooked up to a 4 way 3.5 mm jack, allowing use of a cable with the familiar 3 red/white/yellow RCA jacks at the other end. Audio was wired to both L and R. The jack socket is a barrel design which fits where the old single RCA RF socket used to be, making the mod a no-cut solution, and reversible if you really wanted that authentic murky RF picture back.
Pondering now a couple of routes; tweaking the current comp mod, trying other ones, or trying an RGB mod. I've considered the HDMI mod but realistically I don't like playing analogue era systems on LCD screens; by that point I'd be better off with an intellivision sprint or mister.
Interested if you guys took it any further or found another solution.