Adding a fan to a Coco 2

[Vinnie D.]

Not long ago I picked up a Coco 2 on ebay on the cheap, and thought I'd start exploring its library and hardware. Given how the Coco series has the power supply inside the case, I noticed it gets pretty hot. I've already heat sinked the CPU, but that power supply is still putting out a lot of extra heat next to the motherboard that typical machines with external power supplies don't have to deal with. Given how generous the vent holes are, and how much space is open inside the case I believe I could add an 80mm fan to help dissipate some of that heat. That said, I'm having some difficulty finding much documentation on what is where on the motherboard. I need to find 5vDC that's easy to draw from, and that hopefully won't be missed if there's a little extra draw there. Any suggestions? While I'm at it, what other ICs could benefit from heat sinks?

[hallorant]

I have an first model coco2, a 26-3026, I've (actually by mistake) left it on for days with no serious heat problems. The power supply does warm up, I've never noticed anything else. Good luck with your project.

[jmdlcar]

I just receive the 26-3027 a few weeks ago but I'm looking for a game on a Rom Pak to test my Coco2. If it gets to warm or hot then I will find a small fan and install it inside the Coco2.

[Osgeld]

dont draw 5 volts from the motherboard for a fan

 

the back emf from a motor is going to spike, upwards of -100 volts when the magnetic field collapses on power off, and it turns into a generator which is great for the chips on the same rail

 

the inrush current of a fan is going to do wonders for the regulation circuit, and if the fan ever stalls your going to have a lot more than heat problems

 

its much more work to protect against those two things than it is to give the fan its own power source, even if that source is direct off the transformer with its own rectification and regulation, THEN you gotta think that the engineers back then were not idiots

 

there's a tale of the apple IIc which has a integrated power supply and a floppy drive, when they added a fan the stupid thing overall ran hotter cause it disturbed natural convection currents ....

Edited June 30, 2018 by Osgeld

[jmdlcar]

I could always run the fan from it's own power supply but only turn fan on when need to. And put the fan on the outside at the power supply if it is the hot spot.

[Vinnie D.]

Further thoughts. I have added a fan to my C64 in the past, but it's a very tiny fan drawing a fraction of an amp, and is exclusively for the VIC II chip (as the C64 is notoriously poorly designed in terms of heat dissipation), and it operates without issue. That however is a much smaller fan than I was thinking of for this project. I can see where this could be an issue with a larger one. Well, unlike the C64, as I mentioned before the Coco is pretty generous in terms of the sizes of its vents, and interior space, so maybe a fan isn't right for it after all. From what I've read, only the coco 3 really had overheating issues. I am pretty new to the Coco (more of a C64 guy really, and back in the 80's and 90's it was all IBM compatible PCs for me). So if a fan is a poor choice for the Coco, perhaps some passive cooling would be in order. I've already put a big fanned out heat sink on the CPU. Are there any other chips or components that it would be wise to heat sink?

[Osgeld]

on mine I put one on all the 40 pin dips and the plcc GIME chip

[jmdlcar]

Where can I get heat sink at for the 40 pins at. What do the heat sink look like?

[Osgeld]

I just used some of those self stick ram heatsinks all over ebay, most proper 40 pin heatsinks are glue on, which means you need thermal epoxy for it to work, which is available but not that cheap if you don't use it a bunch