Just upgraded one of my Coleco Vision boards to 4164 memory chips.

[GonzoCV-1]

This particular Coleco Vision was purchased as part of a lot that had bad memory and display glitches.

 

I've been wanting to play with an upgrade rather than replacement route for dealing with the memory on these.

 

So I ordered several tubes of 4164 memory chips.

 

First big fork in the road was that I had to decide whether I would try and desolder all the old ones.

 

Ultimately decided against trying to desolder and remove the old chips. For some reason, the Coleco boards practically disintegrate under a desoldering iron or braid, and I didn't want to goof off fixing lifted traces or whatever. Its just too much work. And I had a pretty good idea about how to wire the new memory in place while taking the 4116s out of the loop by depriving them of power.

 

So I determined to "piggy back" the new chips on the original 4116 chips. This required cutting out (completely removing the pin between the chip and motherboard) the power inputs and ground on the 4116 chips, wiring a jumper on the 4164's, and taking a runner to ground.

 

The result of this was that the "husks" of the 4116's just sit there, they don't get power. Meanwhile, I've kept the -5 and +12 signals from the game board from reaching and frying the 4164's (since they do not use -5 or +12) and I've gotten the +5 source to where it belongs on the 4164 chips for them to work correctly. Sure, its not the most elegant approach... but I also didn't spend more than an hour on it. And it works great.

 

Here ya go:

 

 

 

Here's the "short version" of the mod. If you don't understand these instructions, then you're not technically ready enough to do it yourself.

 

 

Note: Pin assignments on both chips (looking down from top of the chip, pins running vertically, pin one at upper left) are as follows:

 

 

I. Step One: Prep the Board:

 

A. On each the 4116 chips on the board, snip and remove (entirely, i.e., cut off at chip and at board) pins 1, 8, and 16.

 

B. Clean and very slightly tin the shoulders of the remaining pins on the 4116 chips sot that it will be easier to achieve a good connection when you piggy back the other chips on.

 

 

 

II. Step two: Prep the 4164 chips.

 

A. Completely remove pin 1.

 

B. Trim enough off of pin 8 that it cannot touch anything on the board or the 4116s when piggy backed. Leave a little bit of pin still there for the next step.

 

C. Wire a jumper from pin 9 to the remainder of pin 8. Do not cut down pin 9.

 

D. Bend pin 16 out so that it will not contact the 4116s or the board. Tie a short wire to it, for later connection to ground.

 

E. Lightly tin the leads of pins 2 - 7, and 9 - 15.

 

III. Step three: Install.

 

A. One at a time, place one of the prepared 4164 chips piggy back over the disconnected 4116 for that position. Make sure you index it in the right orientation.

 

B. Using a very fine soldering iron, solder pins 2 - 7 and 9 through 15 to their corresponding pins from the 4116s beneath.

 

C. Tie pin 16 from each 4164 chip straight to ground on the motherboard.

 

 

 

Viola!

 

Note: My digital camera sort of sucks, and that's the sort of patterning you see in the video, along with a line near the bottom of the screen catching the refresh. The video memory has nothing to do with the quality of the signal, but really has most to do with whether the pixels and sprites are where they're supposed to.

 

It works great. Since doing that photo above, I have had Frogger running in demo mode for an hour, and the 4164 chips are barely even warm. Compare that to the hot stuff you'll see with the 4116 chips after that long.

 

I'm very pleased.

 

 

Note: If you DO remove the 4116s completely instead of piggy backing, then you've got less work. You don't have to cut pin 16 on the 4164 and can tie it to the same place on the board as pin 16 of the original goes to. (the only reason I prevent continuity for this mod is to make sure there's no ground path for the left-in-place 4116 chips to get them "offline"

[+5-11under]

That sounds like a good way to get the job done.

5-11under

[GonzoCV-1]

That sounds like a good way to get the job done.

5-11under

 

 

Thanks.

 

The original 4116 chips are a disaster. Three different voltages and, if you look at the datasheet, the voltages have to be applied in a particular order --- the -5 first, then +12 (these two polarize the substrate), then finally the +5 for the logic. Also, the voltage is supposed to be removed in just opposite that order.

 

Its no wonder that a dirty Coleco power switch plays havoc with the ram.

 

I've got a little jam jar full of old 4116 chips I've replaced on these over the years (MSX too). With as well as this worked, I'll be ordering as many 4164's as I can get a hand on and simply upgrading the whole board whenever I've got one with flaky original memory chips.

 

And for the Coleco Vision portable I'm working on, this mod will for sure be employed since, along with substitution of a 9918 chip for the 9928, I'll be able to eschew the need for any +12v power supply altogether.

[jsoper]

And for the Coleco Vision portable I'm working on, this mod will for sure be employed since, along with substitution of a 9918 chip for the 9928, I'll be able to eschew the need for any +12v power supply altogether.

I thought of doing this a few years ago, even picked up a beater 99/4a as a 9918 donor, but got too busy with real life. You can probably simplify things by dropping anything needed for the 2600 module. Also, by redoing the controller schematic, maybe by simply switching to schottky diodes, you might be able to drop the -5v supply as well. And most all chips except the sound one should have a CMOS version.

Edited November 29, 2008 by jsoper

[GonzoCV-1]

And for the Coleco Vision portable I'm working on, this mod will for sure be employed since, along with substitution of a 9918 chip for the 9928, I'll be able to eschew the need for any +12v power supply altogether.

I thought of doing this a few years ago, even picked up a beater 99/4a as a 9918 donor, but got too busy with real life. You can probably simplify things by dropping anything needed for the 2600 module. Also, by redoing the controller schematic, maybe by simply switching to schottky diodes, you might be able to drop the -5v supply as well. And most all chips except the sound one should have a CMOS version.

 

I probably won't rewire the controllers to avoid -5. the +12 has been the main challenge, and pulling a -5 voltage using a converter is pretty easy and doesn't cost much in space or battery energy.

 

The biggest thing I want to work on for the time being is to try and duplicate the quadrature from the controllers. I want to have my portable have a rotary control, or even a mini trackball if at all possible. I've got a 64 pulse (256 transition) quadrature encoder that I'm going to wire in place of the reed style one on a super action controller to see if that works. If it does, its a pretty simple matter to wire an optical style situation into it.