Figured out WHY lockups, now to figure how to fix!

[Wayne]

Well, I think I figured out why my Dreamcast locks up and now I just need to figure out how to fix it.

I was able to play some games on my DC after it ####ted locking up by turning it on its side with the fan vent UP (controller ports forward), and a large box-fan blowing on the bottom of the game. I played a couple of problematic games after I ####ted locking up...

The problem seems to be overheating of the several LSI chips on the mainboard. Two of the LSI chips (big square chips) have a sort of grey coating on them that looks like it may be thermally conductive. These chips are directly under the shield which has another heavy piece of metal riveted to it (between the mainboard and the shield).

That heavy piece of metal may be a heat-sink and probably is supposed to come in direct contact with the tops of the chips, to remove the heat that builds up. Apparently the shield's heatsink portion doesn't touch these chips, or at least not well enough.

Now, if I can find some sort of thermally conductive material that I can stick between the chips and the shield, it should sink the heat off of them nicely. Perhaps some square pieces of aluminum or steel, attached to the tops of the chips with thermal tape (usually used for CPU fan/heatsinks on computers). If I can figure out what the space thickness is under the shield, and match it with slightly thicker (1/32nd of an inch, perhaps) pieces of aluminum, it might just relieve the heat sufficiently to play for long periods of time.

There isn't enough room under the shield for any sort of fan on the chips, so this is about the only solution I can think of.

Another possible solution, which doesn't require disassembly of the unit, would be to construct a fan-box that mounts under the Dreamcast machine, essentially the game machine would sit on top of this fan-box. The fan box could draw air from several ports in the sides, perhaps one good sized port in the left, right and back sides (leaving the front closed for appearance), and blowing UP into the bottom of the game...

Anyone have any other ideas - 'cause this seems to be almost certainly what's wrong with my DC, and possibly a problem with other people's machines as well.

BTW: I disassembled my DC all the way down to the mainboard tonight, removing the shield and all, and reassembled it with no ill effects.

[TheMaskedm0m0]

Weird my reply is gone, oh well... also found some more stuff:

####://www.inflowdirect.com/newarsiliipr.html

Premium Artic Silver II thermal compound, increases conductivity between chip and cooler/heatsink.

Temperature limits: - 40C to >160C

Minimal viscosity change from 0C to 150C

Thermal conductivity greater than 8.0 W/mK

2 to 7 degrees centigrade lower CPU temperatures than other thermal compounds.

Negligible electrical conductivity. Arctic Silver II was formulated to conduct heat, not electricity. It is only electrically conductive in a thin layer under extreme compression.

(While much safer than electrically conductive silver and copper greases, Arctic Silver II should be keep away from electrical traces, pins, and leads. The compound is slightly capacitive and could potentially cause problems if it bridged two close-proximity electrical paths.)

Arctic Silver II is now sold in 3 gram tubes. This is enough compound to cover 20 to 30 small CPU cores, or 7 to 12 large CPU cores, or 3 to 6 heat plates. At a layer 0.003" thick, it will cover approximately 18 square inches.

The other thought I had is the mineral oil trick, this guy poured mineral oil into his computer, the liquid is supposed to be non-conductive, electrically. He successfully powered on his machine and it was much cooler. I don't know if this can work inside the DC, been awhile since I last cracked it open.

Secondly, is there some sort of sensor or button that tells the DC the lid is open? If so where can it be disabled or fooled into thinking that the lid is present and closed. My thought was to setup up some computer case fans around the DC, while the top half is removed, to cool it down.

~The Masked M0M0~

[Wayne]

There's a rocker switch on the right rear of the GD-ROM unit, that the lid depresses.

I don't think the DC will hold a liquid. It's not a sealed unit (gaps in the shield, holes in the bottom of the case, etc).

The problem with using a thermal grease or other compound exclusively is that there is a gap between the shield and the two LSI chips. There is a need for a thermally conductive spacer between the two, although I don't know how thick this spacer must be yet because I haven't measured the depth of the shield or the height of the chips. With those two measurements, one could use simple subtraction to derrive a required thickness for the added heat-sink plates.

I would really like to keep the solution self-contained so I don't have to carry added items for the game. Making thermal connection between the shield and the tops of the LSI chips would have a good potential to cure the overheats and allow a self-contained solution.