Nateo

Got a deal on a boxed Odyssey 2 with games on Sunday. Turns out up didn't work on one of the joysticks, but luckily it seems to just be a short break in the membrane. This was also my first year taking my 7 year old son, and he LOVED it. He was telling my wife and I about his plans to set up his own Midwest Gaming Classic in his bedroom ?

Anyone have a schematic available for an AV mod for the O2? I'm seeing plenty of kits online, but I already have the likely parts for one, assuming the transistors use are your normal 2N or BC types. (Heck, I even have LM318 op amps if I can somehow make that work). Thanks!

Yep! All the 1N4148W SMD diodes are on the back of the PCB. I'm still rather new to surface-mount soldering, so this was an excellent chance to get some practice in.

Just thought I'd show off a little of my experimentation with converting an NES game pad go work on a ColecoVision. I designed a little PCB for the keypad buttons, and used little tact switches in order to fit everything in the middle area of the gamepad. Not bad for a prototype, if I do say so myself!

UPDATE: IT WOOOOORRRRKKKSS!! The RAM definitely was bad, but that wasn't the whole story. Bad VRAM might have caused graphical glitches, but the major issue was the BIOS. It couldn't initialize past the startup screen. I ordered a Fast BIOS from Console5, installed it, and it works great now! What a thrilling victory!

Good to know. Thanks for chiming in, I'll give it another test once I get the fresh ROM chip in (that one was also a Mostek, and looked like hell when I took it out)

Also, I sometimes get a fixed tone on boot. Combing through the forums, I found that this might indicate the 74LS138s being shot. Is that worth replacing? I have a couple on hand from a previous repair project.

Update! I got the random character to go away once I replaced the RAM and repaired the traces. Cool! BUT - it still goes to garbage after the splash screen. My hunch is that the BIOS IC is bad as it is also a crummy Mostek chip. I can't help but wonder too about the 74LS138s, as I'm not getting any distinct waveforms out of them on their output ends, just pulling high or low. Shouldn't I be seeing some kind of data coming out of those multiplexers? I wish the CV technical manual had diagrams for how those chips are supposed to look. The Z80 and VDP looked OK when poking around on my oscilloscope and comparing with the diagrams in the technical manual. EDIT: I should also add that the controller ICs are good per comparison against specs outlined in the technical manual.

I decided to bodge the points together that were lifted, since there weren't as many as I was fearing. And besides, I get to do my first trace repair! Fun!

Should be plenty do-able. Thank God clear schematics for the CV are available.

Now that's what I've been needing all this time! Thanks for the link and the recommendation. I did manage to get the rest of the chips out, and by the time I was taking out the last four chips, I got to where I didn't lift any traces or pads. Kinda sucks that I'm gonna have to do some major bodge work to get the circuit going again, but it was a valuable experience dealing with something both incredibly stubborn and incredibly fragile. I have extra 4116's from when I upgraded the memory in my CoCo 1, but I think I might just go ahead and do the 4164 memory mod. Might as well, eh?

Well, I have sidecutters, but I didn't know if perhaps it would be good to have one that's angled in a certain way? Or if there was such a thing for such precision work? My sidecutters can't quite get all the way in-between the pins to cut them clearly.

I imagine clipping out those pins is most easily done with diagonal sidecutters? If so, I should probably pick up a pair before I continue to add to my lifted trace/pad total.

I did check out the blog! And I'm very grateful for your documenting the development of this project!

Excited to see how this progresses. I have what might be a perfect candidate for a transplant with this board given that the RAM in a CV I've been working on has rusted itself onto the mainboard.

I took out two 4116s, and they are far and away the most difficult things I have ever desoldered. Those things have rust eating through nearly every pin, and its making getting them off the board a giant pain. I've only managed to coax two chips to come out, and I've already pulled a few pads and a trace. In other words, the RAM is a basket case. I'm half-tempted to design a PCB daughterboard for the fresh RAM so I don't have to worry too much about damage done to the motherboard PCB while I take out those rust-eaten chips.

Just checked the data lines going to VDP. They turn to garbage right after the BIOS, which makes me think that the 4116s are the next suspect to interrogate. Luckily, I have some working extras on hand that I can use as replacements. Man, I could really use a retro chip tester in situations like this...

Also, is it normal for Mostek RAM ics to have legs that look like this?

Hey all - got an issue with this ColecoVision I've been cleaning up, and it's behavior is unlike anything I've come across. And before you ask, yes, I've cleaned up the power switch and I'm getting the proper voltages ? The RAM I've heard can be suspect, but I kinda doubt RAM would be enough to cause the screen to wig out to that degree. Just wanted to see if anybody had some ideas for possible suspects.

Ok here it is under load: +12v post: 11.61v -5v post: -5.17v +5v post: 4.71v

I did this as well, but only on the power socket going into the console. With no load, I was getting a little under 12v for that rail, 5v and -5v were pretty much spot on.

I did a full disassembly and cleaning of the power switch already. It still doesn't work on the first turn on.

Just repaired a ColecoVision I got for $1 at the Midwest Gaming Classic. All that was wrong with it was the RF Modulator and the power switch, which was cleaned up and reassembled. I performed a composite mod to get around the RF issue. However, something still kinda nags at me with it - it seems it never works on the first power-up. Upon quickly turning the power on and off or pressing the reset button, the console works no problem. Does the fact that the console never powers up on the first try signal potential power supply issues or some such? Thanks!

Damn, this is nice! Can't wait to see the first prototype build!

Just throwing this out there - I'd *love* to see more quality Channel F content on YouTube.