Is there any technical documentation for the expansion modules #1?

[Diederikgr]

I recently acquired the expansion module #1 (the Atari 2600 'converter') and I'm looking at ways to make it work with the RGB mod I'm planning to do on my Colecovision. I'm not having any luck finding technical documentation for the expansion modules (only for the Colecovision itself) and I'm not really equipped to reverse engineer the entire thing. Now I'd like to ask if somebody here has any technical documentation for this module or has attempted something similar in the past.

[Ikrananka]

The only technical information that I'm aware of for the Exp. Mod #1 is that on the ColecoVisionZone website.

 

The Coleco Exp. Mod #1 uses a clone TIA marked as 73192/E4002 and referred to by Coleco as their "custom" Video Interface Circuit. The E4002 has a different pin-out to the original Atari 2600 TIA chip. Now, just to be fair, what I did was to take the information that various people have posted on AA about the pin-out and did my best to resolve the differences. The problem being that there ARE differences amongst the various sources online as to what the pin-out of the E4002 chip actually is. However, it looks like the best pin-out information is likely that in the technical documents on the ColecoVisionZone website. I can draw this up if you want and post it here if it's of use to you.

 

The video output from the Exp. Mod #1, via the CV expansion connector, bypasses the CV video display controller (VDC) (TMS9918A/TMS9928A/TMS9929A) and goes straight to the RF modulator. So, any AV mod on the CV that takes as input the output from the TMS VDC cannot also be used for the Exp. Mod #1. AFAIK, if one does an RGB or F18A mod on a CV, then you also need to do a separate RGB mod on the Exp. Mod #1. The only CV video mods I know of that work for both the CV and the Exp. Mod #1 concurrently are the composite mods that take their input from the RF modulators circuit.

 

AFAIK, the Exp. Mod #1 is almost the same as a standalone Atari 2600. The only things missing are the clock (crystal oscillator), power supply and composite video output all of which pass through the CVs expansion connector.

 

I have planned for some time to try installing one of Tim Worthington's 2600 RGB mods in one of my Exp. Mod #1's but have yet to do so. Hopefully, I'll do it sometime over the summer.

Edited May 19, 2018 by Ikrananka

[Diederikgr]

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.

[mobiusstriptech]

Yeah. I can confirm that the way the Colecovision RGB mod works won't allow for RGB with the expansion unit. I have considered opening mine up to see if I could come up with something for the video but it hasn't been a high enough priority.

 

One thing to keep in mind is that you are going to be limited on what you can ultimately do without just using a video connector on the expansion module itself.

[Diederikgr]

One thing to keep in mind is that you are going to be limited on what you can ultimately do without just using a video connector on the expansion module itself.

 

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.

[Ikrananka]

 

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.

 

The main issue is that although the Exp. Mod #1 VIC (clone TIA) outputs the LUM0, LUM1, LUM2, BLK necessary as input to RGB conversion, the module then combines these signals into a single video (composite?) output signal that is input to the ColecoVision via the expansion connector (connection 33). Therefore the only place an Exp.Mod #1 RGB conversion can take place is within the expansion module itself.

[Diederikgr]

 

The main issue is that although the Exp. Mod #1 VIC (clone TIA) outputs the LUM0, LUM1, LUM2, BLK necessary as input to RGB conversion, the module then combines these signals into a single video (composite?) output signal that is input to the ColecoVision via the expansion connector (connection 33). Therefore the only place an Exp.Mod #1 RGB conversion can take place is within the expansion module itself.

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.

[Ikrananka]

Yes, there are some unused connections (at least according to the only CV schematics we have - attached). Connections 41 and 42 are labelled as having NC (which I assume means No Connection). Connections 29 and 30 don't have any identifiers shown so not sure if they are also spare NC connections. Would four connections be enough for RGB?

ColecoVision Game System PCB Rev. H2.pdf

[Diederikgr]

Yes, there are some unused connections (at least according to the only CV schematics we have - attached). Connections 41 and 42 are labelled as having NC (which I assume means No Connection). Connections 29 and 30 don't have any identifiers shown so not sure if they are also spare NC connections. Would four connections be enough for RGB?

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.

[Ikrananka]

Well, I'm just going with my original plan of trying to install a Tim Worthington RGB mod within the module and have the video out connector also on the module. I know not ideal but unless the outputs could be sent over the expansion connector it will work fine for my needs.