Failure after much work. (STRIKE THAT! BACK IN BUSINESS!)

GonzoMPM-1 · Post by **GonzoMPM-1** » Sun Jul 06, 2008 9:02 pm

I grew up with a Colecovision, so was working on a Coleco portable. As Ben's write up suggests, its a big endeavor. I picked up an old Colecovision for $10 and set to work.

I "flattened" the components, re-soldering where necessary; I removed the metal casing around the RF daughter board and flattened it as much as possible (it cannot be disregarded completely, because the Coleco video chip ouputs Y, R-Y and B-Y instead of composite video, and an IC on the daughter board combines these to a composite signal. I did use a different Composite mod from Ben's, as I noticed the transistor was getting pretty hot, and I couldn't get a setting on Ben's design that worked for both my television and a PS1 screen.

Once the board was flattened, I tested it both with and without a cartridge.

Worked.

Next, on the back of the board I snipped and sanded the rather extended solder points for all the components, as the took rather a lot of space and that's the side the PS1 screen is going to go on, with only a plastic insulator in between (actually planning on contact here, to try and get the case as thin as possible).

Tested, and it worked (both with and without a cartridge).

Next, because I'm doing a "landscape" instead of "portrait" orientation of the portable, I removed the original controller connectors, wired a pigtail to Player 2 (the only output I plan, as player 1 can use the portable); and cut the corners off the board as well as the original expansion slot connection area -- again, going for as much size reduction as possible.

Tested, and it worked.

Next, I removed the original cartridge slot, which is located where my voltage regulators, batteries, protection boards, etc., will be, and mounted it up for top-load where the controllers were.

Wired up the cartridge slot, and tested it.

It works with the cartridge removed (I get the "please power off, etc." message, clear as day), but now it WILL NOT work with a cartridge inserted.

I get a red screen and no response.

Moreover, if you don't let the unit "rest" about 20 seconds after doing so, it screws something up bigtime, because powering on the system WITHOUT a cartridge shows "garbage" characters all over the screen.

I desoldered everything, tested each lead carefully, double checked the traces and pads, and re-wired it again. Its very clean, looks great and everything is exactly where it is supposed to be.

Still won't work. Same exact problem.

I think this mobo is fried.

I'm going to take a few weeks off from this project, and do my NOAC project next. I think these old Coleco systems are temperamental as hell.

If I have to buy a new motherboard and do it all again, I'm going to do a couple of things differently.

1. I'm going to desolder and replace the TMS9928A chip with a TMS9918A chip, a source for which I've already identified. This will permit me to get rid of the RF daughter board completely and free up considerable space. The 9918A is IDENTICAL in all respects except that it outputs Composite video natively. (The 9928A chip was used to permit the Coleco to be localized in PAL and SECAM areas more easily). I'll use a different, flatter heat sink of course, too.

2. I'm going to desolder and replace ALL the inductor coils with more modern equivalents. These inductors are a pain in the ass. They're tall components, they have these little "horns" that get in the way, and I'm just thinking smaller newer components will be better.

3. I'm going to leave the original cartridge slot undisturbed, and simply wire my own to the pins -- or better still, to an extension that will plug into it. The original slot isn't taller than that part of my portable will be, and I'm pretty shell shocked by the recent failure.

In the meantime, I'm going to get a driving controller and a roller controller and see how hard it would be to add those aspects to this design.

I'm already using a home made keypad with tac switches, and though this will not permit overlays, its necessary with the "portrait" orientation anyway.

Dang, I'm upset that this thing kicked the bucket.

===================

UPDATE: Back in business, see post below!

davidm · Post by **davidm** » Mon Jul 07, 2008 8:19 pm

know how feel buddy.

i messed up a nes hand built

Rekarp · Post by **Rekarp** » Thu Jul 10, 2008 8:51 am

What size wire did you use for the cart slot relocation and how long are the leads. Could be that the connections are to far and the wiring to thin.

phantom92opera · Post by **phantom92opera** » Thu Jul 10, 2008 9:15 am

im feeling ur pain. ive put in 100+ hours into my gennyp and just found out my cart slot is a miserable failure

APHawkes · Post by **APHawkes** » Thu Jul 10, 2008 11:15 am

I don't think you fried your mobo. Your cartridge slot may be toast though. The reason I say this is because it will work (somewhat) without a cartridge. Sounds like the components are reasonably intact. The cartridge slot, though, is plastic. It melts easily, gets distorted, etc. See what happens if you remove all the wires going from the mobo to the slot. If the system acts normally you're still safe. I know it'll be tedious, but we always need more practice (de)soldering.

Rekarp · Post by **Rekarp** » Thu Jul 10, 2008 1:30 pm

I think your motherboard and cart slot is fine. Just the wires connecting the two are the problem

phantom92opera · Post by **phantom92opera** » Thu Jul 10, 2008 2:15 pm

nope. hardwired a cartridge to the mobo and no game playback...

jeroen · Post by **jeroen** » Thu Jul 10, 2008 5:00 pm

Stil might be that your wires are to thin.........

GonzoMPM-1 · Post by **GonzoMPM-1** » Thu Jul 10, 2008 5:29 pm

Rekarp wrote:What size wire did you use for the cart slot relocation and how long are the leads. Could be that the connections are to far and the wiring to thin.

That may well be the case. I used the original cartridge slot, and IDE hard drive wire. The leads are all less than 3 inches.

I've shelved it for the time being. I did wire up an old FLOPPY connector (34 pins, cut down to 30) and will try to desolder everything and rewire it again.

I tend to also think that there's something with the cartridge slot, but boy its annoying as heck.

Right now, I'm working on my NOAC in the light gun project, so that will be the order of business until I have the mental energy to hit this project again.

GonzoMPM-1 · Post by **GonzoMPM-1** » Fri Jul 11, 2008 12:40 am

UPDATE!!

It LIVES!

I started thinking after these exchanges that, surely, the video and bios and all other systems had to be "okey dokey" if it could get the boot message.

So I googled a bit about "red screen" on a Colecovision and found frequent complaints about the power switch getting dirty contacts, and the system not getting enough juice.

Well, I've been testing it in this early stage with the original power supply and power switch.

Could it be that simple?

I pulled the project off the shelf and hit the power switch with some contact cleaner. I guess 25 years is some mileage, 'cause when I reconnected my "temporary" composite mod and plugged it in to the television in my workshop:

ZING! The game screen showed up! Ohhh, yeah!

All I can figure is that there was enough juice to power the bios and default message, but once the cartridge was in, there was not enough power or voltage to get everything where it needed to be.

Here's a photo of what the board looks like -- as you can see, I'm using a landscape orientation of the board, instead of portrait like Ben did. The component side of the Coleco Board will face the back of the enclosure. The PS1 screen and board will be on the flat side of the board on the other side. I'm shooting for 1 1/4 inches thick, max, except for the cartridge area.

Here's a picture of the system powered up with an actual cartridge welcome screen displayed.

Woot! I'm back in business!

Rekarp · Post by **Rekarp** » Fri Jul 11, 2008 2:11 am

glad you got it working

phantom92opera · Post by **phantom92opera** » Fri Jul 11, 2008 8:20 am

mine is using ide (ribbon cable) i think about 9" of it ... i tried hard wiring to the cartridge and it didnt work so i will try shortening the wires... we'll see

GonzoMPM-1 · Post by **GonzoMPM-1** » Fri Jul 11, 2008 9:10 am

phantom92opera wrote:mine is using ide (ribbon cable) i think about 9" of it ... i tried hard wiring to the cartridge and it didnt work so i will try shortening the wires... we'll see

9" seems pretty long for this kind of cable.

I'd use your multi-meter to see what kind of resistance you're adding.

Also, if you still have failures wiring a cart straight to the board, make sure you don't have any solder screw ups or pads that got pulled up when you removed the original cart.

I'd take a desoldering braid to the whole area, then examine carefully each trace, and make any repairs necessary.

phantom92opera · Post by **phantom92opera** » Fri Jul 11, 2008 9:19 am

only 1 trace lifted and repaired on the spot when it happened... resistance is about .1-.2 volts