Moded Atari 600XL freezing quite oftenly

[repetto74]

Hi,

My 600XL seems to randomly freeze when used with an SIO2SD reader. It can freeze while playing a game or when typing a Basic program. It does not seem to have an issue when used standalone. When freezing in Basic mode some strange patterns and characters may pop up.

Here is some pictures of the failure. Note that on the RAM test I had a total freeze on first try then it went till the end but with a red square popping up.

PSU is ok, output is normal. Now I made another Memory test and this time the last two blocks are red and the Mem test will crash.

I noticed the crash seems to start more or less around a same amount of time after a cold power up of the machine (IC heating too much?). Now i would like to know which IC's are involved in Ram management. Which are the multiplexer positions on the board?

edit : I opened the case to have a look inside and try to reseat all IC's. I noticed that one of the wiring used for the mod was in contact with a pin of one RAM chip and the insulation was melted. I may have caused a short circuit and hope I only damaged the RAM. The freeze is always popping out after a few minutes which may point to a IC malfunction due to overheat.

Damned hope I did not screw the whole thing up!

[repetto74]

I did not precise that this is a 600xl with the 64k mod which was working properly.

[repetto74]

Again sole testing made which confirm the freeze pops up around 5 min after power up.
If I leave the machine turned on then I will get this garbled screen where I can see text characters of graphic 2 mode. The ANTIC chip may have failed then.

trim.3B7DB790-31AD-45B4-BA17-E282DD67DF0B.MOV

Edited March 25, 2017 by repetto74