Wasted some HOURS trying to work out why the triangle shaped 1.5mm thick piece of solid metal stuck onto the three chips on the Intellivision with heat conductive epoxy glue worked better than various things I tried:
Used a sheet of steel, 1mm thick, from the grounding strip on the N64 console - wasn't easy to get the arctic silver paste to get a match between that and the chips, so after about 4 mins the Intellivision cut out.
Used heatsinks in various combinations using the thermal paste gunk you get in DreamCast and N64 consoles (others use it too probably), far easier to make contact between the chip and the heatsinks as the "gunk" is foamy - after a few minutes the console again tripped out. (?)
Used large metal plate, and thicker heatsinks, same result. This is nuts - there is no way bits of metal are better than proper heatsinks. Applied a fan nearby, same result. Getting a pattern here....
Tried tying sheathed wires around the chips to secure the heatsinks in place to ensure good contact - same result. Definately a pattern here; system tripping out.
Remembered something in the back of my mind from something I read about ages ago, and have vague memory about from 30 years ago - "sleep mode"
So, after all that messing about and a few wasted hours, I can report that after trying various methods, all of which it turns out would have worked fine as the chips get hot but with metal plate on top or heatsinks only get warm to touch only, I have now put on a 1mm plate of copper onto the thermal paste gunk to connect to the chips - works fine, not very warm at all, no issue being in a portable without a fan, let alone my Alpha Omega system.
The beauty of using the copper plate (could have used the steel, although copper is better as conducting heat away from a source) is that I have a nice flat piece of metal with no further cutting needed. The metal, as quite thin (1mm thick) lays low on the casing so the system is as flat as it can be. I need now to do the following work on this console:
* Secure the copper plate to the board so it doesn't move off
* Relocate components that are taller than the chips with the plate on top - ie a handful of capacitors, if that - or bend them back and elongate their contacts a bit with a tiny anount of extra wiring to one side per capacitor so it lays flat enough against the board
* Remake the composite mod I received (will review that later) with components i've bought, so the composite circuit lays flat on the console board in the space where the old RF box used to be
* Arrange the system on the foam mounting board with the SMS and NES on the other side of the board.
* Relocate the daughter board that generates the video signal before it goes to output - shown in pic below, to the top right of the pic:







