Bad PCB or bum chips?

[Gaztee]

Wonder if anyone here has a bit of insight to my problem?

 

Of all my coleco games (not that big of a collection!) I have 2 carts that just refuse to work. Finally decided to remove them from their homes & have a good clean of the connectors to see if I could bring them back to life.

 

Well after using alcohol wipes, brasso & an eraser neither game works. One of the PCB's appear to have a bit of corrosion on one of the rear connectors. This game does nothing when inserted to the console. The other one just brings up the switch off before inserting cart screen.

 

Any ideas what is causing the problem? If its the chips are they re-writeable? Or do I have to locate some replacements?? Or is it likely to be the PCB's in which case I'm assuming they might as well end up in a bin!

 

Thanks in advance

Gaz

 

PS the games were Donkey Kong (UK) & Cosmic Avenger (French)

[+nanochess]

When cleaning with alcohol also clean the whole PCB by the two sides and around the chips pins (both sides), this has solved me various dead Activision cartridges.

 

If you insert the bare PCB in your Colecovision (chips towards you,) be sure to put a piece of cardboard between the PCB and the movable cartridge gate (it's conductive)

 

And if still it doesn't work, congratulations! you've a fine piece of electronics trash

 

You can replace the chips with EPROM chips and reprogram same game or another game , you'll need soldering equipment and an EPROM programmer, though.

[Gaztee]

When cleaning with alcohol also clean the whole PCB by the two sides and around the chips pins (both sides), this has solved me various dead Activision cartridges.

 

If you insert the bare PCB in your Colecovision (chips towards you,) be sure to put a piece of cardboard between the PCB and the movable cartridge gate (it's conductive)

 

And if still it doesn't work, congratulations! you've a fine piece of electronics trash

 

You can replace the chips with EPROM chips and reprogram same game or another game , you'll need soldering equipment and an EPROM programmer, though.

I'll grab myself some more alcohol wipes tomorrow & try the whole of the PCB as recommended.

 

I've no problem inserting a bare PCB at the mo as my coleco is topless

 

Which Eprom chips are used? I have a friend with a burner that should do these so, hopefully they can be restored to their rightful working state.

 

Thanks for the info

[+5-11under]

If you put an EPROM in, you'll need to make sure the chip select lines are dealt with (they probably aren't).

[Gaztee]

If you put an EPROM in, you'll need to make sure the chip select lines are dealt with (they probably aren't).

That the trace lines on the pcb??

[+5-11under]

If you use an EPROM, you need to "AND" the 4 incoming enable lines (for a 32K game, anyway) to the chip select or output enable of the EPROM. Use an AND chip or resistor/diode logic. See the CV schematics.

[+nanochess]

It depends, you'll need either 27C64 (8K) or 27C128 (16K). The images for games can be easily found in the Internet.

 

Donkey Kong can be either 16K or 24K size (supposing 3 8K memories,) I don't remember about Cosmic Avenger.

 

If you use same memory size as original game there should be no problem with replacement.

 

It would be very useful if you could put pictures of PCB to see chip numbers and style. I remember my own Gorf cartridge containing EPROM memories, so it could be erased theorically and reprogrammed.

[Dr. D.]

Another possibility is cold solder joints on the chip legs. If you are handy with a soldering iron, you can reheat/resolder each pin. You can then verify continuity with an ohmmeter. As another poster above stated, knowing the PCB layout is needed to determine which pin should be attached to which edgecard trace.

 

*Dr. D.*

[Gaztee]

Here's a picture of the chips.

[Dr. D.]

My collection of ROM images shows "Donkey Kong" and "Cosmic Avenger" to be 16K games, so these PCBs are each 2 X 8K ROMs. The schematic is no doubt the same as "Time Pilot", which I reverse-engineered for the prize cartridge I gave at ADAMcon 25 this summer. Below is my drawing (apologies, it's rough) of that schematic from the hardware presentation I did at ADAMcon:

 

[+nanochess]

Here's a picture of the chips.

 

I thought it was going to be easier! but these are 24-pin memories, the common 8K EPROM is 28-pin.

 

My collection of ROM images shows "Donkey Kong" and "Cosmic Avenger" to be 16K games, so these PCBs are each 2 X 8K ROMs. The schematic is no doubt the same as "Time Pilot", which I reverse-engineered for the prize cartridge I gave at ADAMcon 25 this summer. Below is my drawing (apologies, it's rough) of that schematic from the hardware presentation I did at ADAMcon:

 

 

Thanks a lot! this has served me to compare with 27C64 EPROM, the PCB would need adaptation .

 

Not impossible obviously, but unfortunately not easy.

 

[Dr. D.]

I thought it was going to be easier! but these are 24-pin memories, the common 8K EPROM is 28-pin.

It's the difference between a mask ROM (which is manufactured with the program in it, right on the silicon die) and a PROM or EPROM (which starts as a blank and is then programmed externally). Mask ROMs thus don't need as many pins, and in large quantities, are/were cheaper to make. Of course, if you found an error in the program, you had to throw away all the ROMs and make a new batch from scratch. That's why EPROMs are used for prototyping: you can change them.

 

this has served me to compare with 27C64 EPROM, the PCB would need adaptation .

Not impossible obviously, but unfortunately not easy.

Building an adapter to reuse the circuit board would be ugly. After desoldering the old chips, you'd have a spaghetti mess of point-to-point wiring from the old holes to the new pin positions on a low-profile 28-pin socket. And once you put the new EPROM in such a socket, you'd have a hard time getting it out again because the socket would be "floating" on the wires, hard to pry up against. But it could be done.

 

If you went to the trouble of desoldering the chips, you could test them with a PROM/EPROM reader. If the program stored in them verifies against the binary image of the game ROM, then you know that the problem is in the circuit board. But an ohmmeter test of pin to edgecard pad would be an easier way to verify the board tracing integrity. Desoldering is tricky.

 

*Dr. D.*

Edited September 6, 2013 by Dr. D.

[ColecoFan1981]

The ROM on the left has chips made the 36th week of 1983 which would be the week of September 5-11.

 

The one on the right has chips made the 23rd week of 1983 which would be the week of June 6-12.

 

~Ben

Edited September 12, 2015 by ColecoFan1981