Falonn

For completeness: we haven't tested compatibility with any other systems besides Colecovision yet, though there isn't anything Colecovision-specific in the circuit. My confidence is high that it should work anywhere the '992xA series VDP has been correctly integrated. Better news: I have seen the exact same mod board working on both an NTSC and PAL system without any changes. So that seems to bode well for compatibility, too. If anyone decides to try it with a TI-99 or otherwise, it would be great to hear about positive (or negative ) results! As for that list in the documentation, I did my best to track down which products in the 80's used the '9928. It's tricky because there seems to be a lot of (slightly) incorrect information out there. (E.g., I've seen Colecovision described on more than one website as having a '9918 which has never been true as far as I know.) You guys would know a lot better than I would: was I correct in listing the TI-99/4 as using a '9928A? Thanks!

You're right, that part is a little hard to follow. I used that angle because I thought the desoldering was more interesting than the wire itself (and because I already had the shot set up from the previous step 🤣 ), but you make a good point. Without another un-modded Colecovision to shoot more video, I just went back and added three more seconds of footage to that section and added a little text overlay to try and smooth it out. (You may need to force-refresh the page to get the new video to show up. Old video is 55s. New video is 58s.) I'm just the RGB guy. Last I heard (from MrPix), the follow-on S-video board was being adapted from an existing product, so I can't imagine there'll be as much work involved. I don't remember ever hearing a time estimate about it though. My dream solution is still an RF board replacement that passes along the composite video from Expansion #1, provides a great no-cut mounting point for the output jack, and adds S-video all in one fell swoop. That's a larger project, so I don't know that anyone is working on it at the moment. Absolutely! The idea behind making the project open-source from day 1 is that everyone should have access to this stuff. The more people out there building and/or installing them, the better access everyone has. So you've got my vote. Just let me know (via PM, email, etc.) when you'd like to be added there (and the URL I should point people toward, if any) and I'll post it right away. Same goes for the list of assembled board sellers. I'll let you guys duke it out on price or whatever. I'm just here to shout from the rooftops that this mod exists and to try and help facilitate getting it into the hands of as many people that want it as I can.

Alright, the official launch thread for TMS-RGB is up, over here.

TMS-RGB is an RGB mod for Colecovision (or anything else that uses TMS992xA graphics). It's completely analog, introduces zero latency, works in NTSC and PAL systems, doesn't require any tuning, and can be installed easily. It's Open Source Hardware and can be built (and sold!) by anyone. We've been working on it over in the other thread since February and it's finally ready to officially launch! Ruggers Customs was kind enough to test a few of the v2 boards against dozens of combinations of Colecovision motherboard revision and RGB cable/receiver. Everything came back with a clean bill of health (with the exception of an HD Retrovision YPbPr adapter which behaved poorly compared to every other test). This mod solves the known issues---including the dreaded "too much blue" problem---of all known RGB mods. Full Information Website: https://tms-rgb.com The website contains a lot of stuff including a list of installers, a list of people selling pre-assembled boards, DIY installation instructions, and from-scratch board assembly instructions. Highlights include: watching my shaky hands with tweezers, watching my shaky hands with a soldering iron, some diagrams showing a couple of the possible output jack connections, a little tool to automatically build a full Digi-Key shopping cart with all components (for however many boards you want to build) in one click, and a video on the front page that I had too much fun recording and editing. The development story page may also be of particular interest to the community here, as you are featured in it! Let's call this the official support thread for anyone building or installing one. Feedback I'd love to hear about: anything that is unclear or missing in any of the guides. A special thanks, again, to ChildOfCv, MrPix, and Ruggers Customs.

You're looking for @Ruggers Customs (also: http://ruggerscustoms.com/ ). Jimmy is as reputable as they come and he coincidentally just helped with the final testing of the new TMS-RGB mod across half a dozen Colecovision revisions.

No need to be sorry. The more I've investigated, the more I've found these things hiding in the cracks. I only spotted this attempt from New Zealand a few weeks ago (where they had RGB output for the SC-3000 in mind instead of the Colecovision). It looks like they went through a lot of the same steps as we did here, only three years ago. I wouldn't be surprised if there were another half-dozen people that have worked on the same thing over the years.

That's the "Hackaday" circuit in this comparison back on page 14. The sample-and-hold idea used in TMS-RGB comes from that one. It had a great, original idea on how to solve the too-much-blue problem.

The remapping that Ruggers Customs uses supports a lot of (most?) use cases. It might not be a bad default with options beyond that for the games that don't fit as closely. That (still being produced) model has 8 buttons including Start and the shoulder button.

"Too much blue" is a well-known problem in ColecoRGB and several older RGB mods. I've never heard of a small voltage difference causing it to come or go, but the whole circuit (with its "tuning") is balanced precariously, so I wouldn't be surprised. A better answer might be to swap your RGB mod over to TMS-RGB which works around the root cause of the "too much blue" and several other problems. (I'm a couple days from posting the whole set of build and install instructions.)

I've daydreamed about a hobby display project involving those tileable LED panels. They're designed for big, unbroken full-wall displays but if you only need 240p, it would only take a few panels and end up around a normal TV size (and not be too crazy expensive). I've never seen one in person, so I'm not sure if you'd need to add a diffuser layer to get a convincing picture at living room distances. But, if driven the right way it should be competitive with CRT's speed and latency. All light guns would work on it natively. It hasn't left the daydream stage, so I don't know any of the details: whether you can drive them without PWM, whether the addressing can be set up to do vsync-like line-by-line scanning, etc. Still, it's seems like a neat idea since those panels are ubiquitous and cheap now.

I'd been wondering why the 75Ω output resistors I've been using were labeled "85X". How "helpful" of them. 😅

Just another data point: my Mean Well-based PSU arrived a couple days ago and I'm also impressed by the build quality and reassured by it being from a "real" manufacturer with all the various UL certifications, etc. It seems like it will be less likely to go up in smoke the way CrossBow's ColUSB did, especially by removing the third-party USB adapter wildcard. I was very happy to measure 5.165V on the 5V rail, which is much closer to the OEM power supply than the 5.00V measured from the ColUSB. So it should be less likely to have any brown-out problems once it makes its way through the spidery power distribution network. I haven't tested as thoroughly as CrossBow, but at least through the new RGB mod (TMS-RGB v2), I didn't see additional noise of any kind. Granted, I only tested through the Framemeister, which already does a phenomenal job of cleaning everything up...

Just a quick note: the v2 boards arrived, they work great, the holes are plenty big enough, I built a few and sent them over to Ruggers Customs, he's got them now and will hopefully have wider testing results soon. In the meantime I've got all the video shot & edited for board assembly and am sitting down to do the same for mod installation. With any luck a nice, easily-installed RGB solution is imminent.

I was planning to (when the instructions are finished).

Sounds good to me. I don't know about the compatibility of the UM-1662, but at least it will give me a chance to finish the installation instructions for the RGB mod.

My understanding is that you can solder them if you want to completely bypass the potentiometers, leaving the board unable to be adjusted. I reverse-engineered the schematic back in February, over here. You can see the three jumpers in the middle of the PDF page and how they let you skip past GRN, BLU, and RED. I know the OSH Park link for ColecoRGB 1.2 says "if you do not get sync, try adjusting R23," but I wonder if the better advice right now isn't "wait two days for TMS-RGB"? 😉

Yep, just adding a little extra solder to five or so pins. It's not so bad if you've already got an iron. When I'd mentioned why I was interested in it to the seller, he said (via PM) that it would be cool if his system was able to help the community in some way. I think it would be cool if it could keep doing the same! A set of PAL schematics at the level of your NTSC set would be like, 100x more valuable to the community than my quick double-check that an RGB mod works. PM me whichever address you'd like a PAL Colecovision to materialize when I'm finished testing these v2 TMS-RGB boards in a few days and I'll send it along on the next leg of its journey. Really, this is a weight off my shoulders: I didn't have any idea what to do with this thing---besides storing it indefinitely---once the testing was finished. Having it be useful to someone else would be great.

FWIW, I just got the shipping notice from OSHPark. Their half-thickness board service doesn't have any rush options, so it took the full two weeks this time. The tracking number says the v2 boards should be here Monday. I'll have the first results overnight. My confidence level for the smoke test is high: the schematic is unchanged and all we did was make the PCB layout better. Assuming that goes well, I'll be sending a few assembled boards to Ruggers Customs to test against a pile of different Colecovision revisions. I'll leave it up to MrPix whether he wants to wait to hear back from that round of testing before he orders a bunch of these. For my part, seeing it work perfectly on a PAL Colecovision is enough to raise my overall confidence level pretty high. That's just about the most-different environment you could imagine, so if it also works there, it should work everywhere. I've got a fair chunk of the instructions site finished locally. Most of it has to wait for these final PCBs before I can start taking pictures and recording video, though. I hope to have most of that done during next week, too. EDIT: Er, it looks like the shipping notice was for a couple more 8-pin DIN breakout PCBs and the new test jig boards, which were both using their standard stack-up. The half-thickness TMS-RGB boards themselves are supposed to come back from the fab a day later. So with any luck "Monday" above should only become "Tuesday". We'll see.

Assembling a board is a little trickier, but assuming you can buy one pre-assembled, the installation isn't much more than placing the mod PCB over the graphics chip's pins on the bottom of motherboard, then adding solder to five standard DIP through-holes. Beyond that, you'd just need to run the output pads to any style jack of your choice (8- or 9-pin mini DIN, or directly to SCART, I suppose, if you don't mind cutting that large of a hole in the case). ... on second thought, that little removable panel at the back of the PAL version of the case looks just right for a SCART connector. I bet that same case was used for both the PAL and SECAM version of the console.

Just for reference, here's the other side of that RF board. Apparently the system I just picked up for PAL testing for the new RGB output board ("TMS-RGB") is exactly the same as Oldschoolgamer1's: 91162 Rev.D motherboard and 91194 Rev.B RF board with a UM-1286. So I suppose the good news is that you can be reasonably confident it'll work with yours. Who is Mr Big? 🤣

A more common cause for that problem is a dirty power switch. Cleaning the contacts or replacing it might be an easier troubleshooting step than doing the 5V VRAM mod.

This is definitely a PAL system. Most of the tutorials and guides out there are for the various NTSC revisions. They're completely different designs, so an NTSC Rev.D won't look anything like a PAL Rev.D. While the components are fundamentally the same, they're all in different places and they've all got different labels. (I don't have any answers for you, sorry! But hopefully this sheds some light on why it's been hard to find answers so far. It would be cool if the community was eventually able to bring the information available for all three versions---PAL, NTSC, and SECAM---to parity.) I hope someone else can help you!

This had me worried, so I measured. With no output (RF board removed, no RGB adapter), the 5V rail (measured across my CV's now-removed power switch) was showing 480mA while at the Popeye level select screen. With only RF: 490mA. With only RGB: 600mA. With both: 610mA. That's less scary. There's still a lot of headroom. I can't believe how efficient the RF board is! If it was power hungry, I was worried the recommendation might have to be "remove it to make more headroom" but it barely registers. Otherwise, I haven't tried any of the expansions to see how much power they use. The half dozen circuits you can readily find in a Google Image search all show them floating. The RetroTINK Comp2RGB leaves them floating. The diagram on page 2 of the datasheet shows little switch icons that imply they're disconnected when not in use. This whitepaper describes the video switch portion of the IC as a mux, which implies you can leave them floating. And when I asked just now, this TI engineer said we could leave them floating. I meant L6 & C48. It's not much, but they condition the power a little. I was worried L6 might have developed some resistance somehow. (It hasn't.) This was bugging me so I set out to solve the mystery and see where the voltage was going. After ~50 measurements across three CVs, three power supplies, using two different instruments, I'm satisfied that I've got a much clearer picture. The good news is that we're doing just fine voltage-wise. User error and poor testing methodology were the straw that finally broke the camel's back and made it appear below 4.75V. About a week ago, I noticed my nearly ten year old, $11, never-calibrated multimeter wasn't giving me the answers I wanted. The LMH1251's datasheet goes out of its way to describe a very high quality 10k Rset resistor, so I went a little overboard for these test boards and got a 0.1% tolerance part just because I'd never seen one in person. Excited to see a perfect "10.00" on the meter, I had a bit of a revelation when they were all showing 9.96k or so. During the past three months, every resistor seemed to be measuring just under its value and now I knew it was the meter and not the parts. (My Fluke 87V should be here on Friday.) 🤣 Suspecting the same was probably true of the voltage readings, I wanted a second opinion. Using an oscilloscope as multimeter is pretty clumsy, but it shed some light: my awful meter is universally 60mV lower than it should be when measuring using its 20V setting. I dialed my digital benchtop supply to 5.000V. The scope showed 5.00V. The meter showed 4.94V. In every other measurement, the offset was identical. So lesson #1: make sure you can trust your tools. 60mV is a fair-sized chunk, but still doesn't explain the rest of the missing voltage. So I went looking. Instead of finding a single smoking gun, it was more like death by a thousand cuts. All of the following numbers are from the scope's more accurate measurements. Touching the probes directly to the 5V ColUSB pins: 5.00V. Touching the probes directly to two separate OEM Coleco power supplies: 5.10 and 5.12V. So while the ColUSB does a faithful job of regulating voltage, I wonder if the CV PSU isn't designed to go just a tiny bit higher to combat some of what's coming next. (That or they're just getting old and out of spec.) 😅 Plugging the (perfect, 5.00V) ColUSB into the jack and measuring just on the other side of the rivets: 4.94V. I'd tried adding a bit of solder to each of the clamp-on style rivets, but it didn't seem to have any effect. Measuring at the white/black wires running into the CV board: 4.90V. Measuring at the expansion port: 4.86V. Measuring at the TMS pins: 4.83V. I had noticed once (while switching between systems) that 100mV had gone missing until I re-seated the power cord from "firmly" to "very firmly". So apparently every little bit counts. The last measurement was from the TMS-RGB breadboard VCC and ground rail, which comes from (about 8") wires soldered directly to the same TMS pins I just probed, but showed 4.76V instead. Testing these same points on the PAL system showed the same or slightly improved values across the board. So, between a low-quality meter, a most-likely poorly-seated power cord, a ColUSB which is 0.1V lower than the OEM PSU, and measuring the voltage from a distant breadboard, I think I can account for most of the loss. In the typical case, with the RGB board soldered directly to the VDP, using an OEM power supply, it should be seeing something closer to 4.9V, which makes me feel a lot better. Don't forget that about an inch away from the TMS's VCC pin we've already got C106: a 10uF tantalum.

The 4.6V is measured directly from the TMS9928A pin when nothing is connected to it. It's the same whether using an original Colecovision AC adapter or a ColUSB. So I'm not really sure what's going on. Maybe the voltage regulation system on the CV board is dropping a little voltage somehow?

Final v2 boards ordered over the weekend, new voltage dividers tested, new resistors ordered just now, and the schematic, board, and test jig have been updated! The new dividers consume around 15mA less at all times with no apparent difference to the output: That's a little friendlier to the 4-channel amp and to the Colecovision's power supply. The impedance is matched a lot closer between all three lines (though it doesn't matter much in this case). And I was able to consolidate one more BOM line. An interesting detail: when I ran VCC through my multimeter to measure the current, the colors on the TV were noticeably incorrect! Apparently the burden voltage in my entry-level meter is pretty awful and it was enough to drop the already-low ~4.6V that I can see right off the TMS VCC pin down to around 4.3V. That's low enough that we're starting to creep out of spec on a couple of the ICs. This is a non-issue (and I switched to performing the measurements using my bench-top supply instead, where I can compensate for the drop), but it does make me wonder about any of these old machines that might be in particularly bad condition. If the 5V rail were to droop much more than the 4.6V I'm already seeing on mine, it might undermine much of our effort to get accurate colors. Right now I'm going with "I hope that won't be the case" and "if it drops that low, the console/computer itself will probably stop working before this board does". It would be more work to jam a tiny 5V boost regulator on this board (and I don't think we need to). Here's v2 (see attached PDF for zooming, copy-pasting, etc.). There aren't many schematic changes since v1: a couple capacitors removed, a couple fiducials added, the resistor values between U3 and U6 updated, and the parts have been renumbered to match the new PCB layout. The Eagle files are in the GitHub repo. The v2 PCB is very likely the board that's going to make it out the door (again, thanks to more than a hundred incredible suggestions across thirty-five PMs from MrPix). We'll mostly know in a week when they get here. We'll know for sure once I build a couple, send them to Ruggers Customs, and he tries the board on like ten different CV revisions. While I wait for them to arrive, now will be a good chance to get a head-start on that instructions page. TMS-RGB v2.pdf