Diederikgr

Congrats on keeping the enthusiasm on such a project, anything electrical engineering for hobby takes long. It's a bit of a drag when you order parts, do some testing and find errors, and then you're off to wait another couple weeks again. I'm curious how many PCB alterations you've gone through?

There's still people not familiar with the internet. A thrift store I volunteer at once had this really nice turntable come in, ended up auctioning for €450. Looking the thing up online I found that the dust cover alone goes for over €100. I also managed to get a good deal on an Amiga 500 from there (after a fair discussion with the manager).

You might be right, the Saturn also seems to go there (at least in Europe). They've started to get to that €100 mark, but thank god this system was a hit in Japan and getting them from there is dirt cheap. It'll take awhile before the ps3 and 360 get really desirable, but supply migh take care of itself with so many 360's still getting the infamous red ring. To the OP: Change your expectations. The Jaguar has gotten a bit silly in the last couple of years, but decent deals can still be found. Couple weeks ago I paid €150 for one including Tempest and some other games, which is about the same as I paid for my NES if I include the cost of the mods (mainly the RGB mod) I did for it.

Buffers from my understanding. These are used to minimize the load of data lines. In this case every signal going in and out of the cartridge. It's possible that even those chips got a load too big to handle.

Thanks for pointing me to those chips, because I now notice something a little odd there. U14 is a TI chip in my case. Console5 mentions that U12 and U14 are the same chip, though U12 in both our cases seems the AC variant (not HC). I also don't notice any damage to any of the chips, all chips still have smooth surfaces.

So I got my hands on 2 Jaguars at the moment. One's absolutely fine, but the other one only red screens. First attempt was cleaning the cartridge connector, no luck. Second attempt was adjusting all pins and replacing all capacitors, red screen! Third attempt was replacing the cartridge connector and guess what, still a red screen! So now I've let the system sit on the red screen for 10 minutes and see which chips get hot. The big ones all seem to heat up just fine, except for U35, the big chip closest to the DC connector. This chip remains stone cold. Console5 mentions this is a ROM chip, so it doesn't seem too odd that this is the culprit. Anybody ever traced the issue to one of these chips or has more knowledge on where to go from here?

That'll make it a little easier as I have a couple of Sega psu's laying about, but I'll check the polarity either way. Just that the Jaguar has nothing to protect itself against reverse polarity has me a bit worried. I'm guessing this is a must as I'll be getting a PAL version. Good thing it seems as easy as on the Mega Drive (Genesis).

So I'll soon be getting my hands on a Jaguar after being on the hunt for one for awhile and was wondering if there's any weaknesses to keep in mind with these things. The Lynx for example had quite a poorly designed (in terms of safety) voltage regulator that could pass the batteries' or AC adapter's voltage directly to the sensitive IC's. I've been reading that the Jaguar is also a bit problematic with power as there's no safety for reversing the polarity of the AC adapter. People apparently killing their Jaguars when they plug Mega Drive or SNES power supplies in.

It plugs in place of the LM1886 on PAL models only. Developing an RGB board for the NTSC variant is a different beast entirely as I don't think there's anywhere to pull digital RGB signals from.

So for my study in electrical engineering I had to design a single pcb, but I actually ended up designing multiple. The first one was an RGB board for the Colecovision that converted the analog video signals into RGB. With the schematic I built it from being quite sketchy, I'll only share it if it delivers any decent results. The second PCB is one I'm a little more confident with. There used to be a board like it called the Zoe (kinda wanna call it the Joey), but it was apparently a tough one to get. I also didn't like the idea of soldering 10 wires to the PCB. My idea is to imitate what Tim Worthington has been doing with the NESRGB and 2600RGB boards, where the modboard sits in the socket of the IC it takes the signals from while still leaving the IC functioning the same. This method is more work, especially if the IC isn't socketed to begin with, but leaves a much more tidy result. I also went with SMD components over through-hole as this allows for a smaller PCB, although it may scare the hobbyist away from it. The three IC's will be tough, but the other components should be easily doable with a soldering iron. The board also houses an additional pin header to do a composite video mod, which will require soldering a single cable to the Intellivision's board. Considering this is just a 3 bit DAC (times 3) I also tried making it with Opamps, but wasn't succesful in simulating anything functional. I didn't want to include a negative voltage on the board to use different opamps, and couldnt get anything working with single supply opamps. I'm not an electrical engineer quite yet, so my attempts only take me so far.

It can easily be done over 4 pins, you just need one for each of the RGB colours and a sync. Of course you'd need audio too, but that seems to have its own pin. But from my own look, pin 29 and 30 are definitely not usable as they do seem to be hooked up to some logic chips. I think getting the RGB signals (or the TIA signals) over the expansion port isn't a good idea. That would indeed limit the options to putting a video connector on the thing itself, or finding an alternative to feed more signals into the Colecovision.

Is there not a couple of unused pins on the connector? I do think I'm spotting a couple on mine, but I'm not finding a pinout for it in my documentation.

It's a rather tough engineering challenge to get it to work with an RGB mod over the Colecovision itself, but putting a video connector on the unit itself just defeats the purpose in my mind. I do want my expansion port to still work with the other modules (including the SGM), so it's even tougher. I might just have to hold out on attempting to mod the module and get my actual Colecovision RGB modded, but leave some space for future modding attempts.

Thanks for this very well laid out response. That documentation is rough and some pages are a little tough to make out, but it's a good bit of documentation still. The biggest problem I think I'll have is that I'm working with a PAL version of this module and it has a different TIA (or VIC), a VTI branded chip marked 342VA1382/13717/VF4023-0001 (none of these markings result in anything useful on google). My unit also does seem to have an oscillator crystal on board, meaning it'd be even more different than the NTSC version. Using Tim Worthington's 2600RGB board would be incredible and I would like to see you succeed with that. I already have some really good results with that in an actual 2600, but I don't dare to try it out for the expansion module. I'll include a picture of what my module looks like, but I fear it's too different from the NTSC model.