Got a Colecovision for repair which had not worked in a few years. Had never seen or worked on a Colecovision before so had to do a bit of research on the typical failure modes.
Top of the list were a faulty power switch and the video RAM as possible suspects. The power switch had already been changed and the VRAM replaced on the unit, the older 4116 RAM chips upgraded to single supply 4164 devices.
Measured the 5V rail across various chips at ~200mV, so something obviously pulling it down. VDP TMS9929A at fault here, replace the VDP and signs of life at last.
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| Where's the Kong ? |
Unfortunately a bit of garbled mess still. Ran a continuity test on the VRAM address & data lines turned up a couple of broken tracks.
The 4164 RAM was soldered to the board when the previous upgrade was carried out, decided to remove all the RAM to check out the tracks properly and refit the RAM in sockets. On inspection the board was quite burned under of the RAM chips, the original 4116 IC must have badly overheated at some point.
Repaired the broken tracks,fitted the RAM in sockets, replaced the RF output with AV output and the Colecvision lives to fight for another day :)
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| Ah there he is.. |
Hi,
ReplyDeleteMy coleco show screen like this:
http://derbian.webs.com/c64diag/fault.htm?id=c19_1
Any help? the RAM its 10,90V in +12V line. mmmmmmmm
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