quick hw question - best place to pull 5v on 1200xl?

[cephallus]

Since I'm cutting away a part of the heatsink to mount a cf card reader, I was thinking of installing a small 5v fan. Any thoughts as to where the best place to pull power for it would be?

 

As always, thanks!

[classics]

There are two 5v regulators attached to the heat sink. You can get 5v off the right most leg of either, and ground off the center.

 

This is before the power smoothing components, so any noise from the fan should be minimized.

 

Do keep in mind a fan is probably going to draw in dust and dirt. One of worst mod problems I've ever seen was the inside of a 1050 where someone had installed a fan in the top case. The whole inside of the drive was just caked black with grime and dirt and other filth the fan pulled in.

 

Steve

[Bryan]

Looks like the positive side of C41 (in the back by the heatsink) is a good place to get it.

 

Edit: (basically what Steve said. C41 comes right off one of the regulators)

Edited July 28, 2008 by Bryan

[cephallus]

thanks guys!

[+bob1200xl]

You might take notice that there is a place on the heatsink that was designed for a third T0-220 device. If you are going to cut away that side of the heatsink, it seems to be overdesigned - you probably won't need a fan. At any rate, I'd take it from C40, which feeds memory rather than C41, which feeds the Big Chips. Just in case you do an upgrade that adds load to the Big Chips. Actually, a 12 volt fan might be better - take power from before the regulators.

 

Bob

 

 

 

Since I'm cutting away a part of the heatsink to mount a cf card reader, I was thinking of installing a small 5v fan. Any thoughts as to where the best place to pull power for it would be?

 

As always, thanks!

[Bryan]

At any rate, I'd take it from C40, which feeds memory rather than C41, which feeds the Big Chips.

 

My schematic shows it the other way, with C41 feeding memory (+5B).

[cephallus]

You might take notice that there is a place on the heatsink that was designed for a third T0-220 device. If you are going to cut away that side of the heatsink, it seems to be overdesigned - you probably won't need a fan. At any rate, I'd take it from C40, which feeds memory rather than C41, which feeds the Big Chips. Just in case you do an upgrade that adds load to the Big Chips. Actually, a 12 volt fan might be better - take power from before the regulators.

 

Bob

 

I actually have a 12v fan that is roughly the same dimensions (around 30mm by 5mm). So same question, but 12v - preferred place to grab the 12v? Anywhere before the regs should be ok?

 

Unfortunately, the 1200xl schematics I have are really of abysmal quality...

[classics]

12v is on the left leg of each regulator.

 

~12v IN - Ground - 5v Regulated OUT

 

Keep in mind the 12v is probably very noisy and unregulated. It could be as high as 21v, it depends on the power supply.

 

Steve

Edited July 29, 2008 by classics

[cephallus]

You might take notice that there is a place on the heatsink that was designed for a third T0-220 device. If you are going to cut away that side of the heatsink, it seems to be overdesigned - you probably won't need a fan.

 

I took a look and ya, I didn't notice that earlier. I am reducing airspace inside the case already with an internal MyIDE/ribbon-cable/cf-reader, am adding a second pokey, and have the Rambo installed. The little 5v fan I have is extremely low power (and low volume, like .5cfm), so I'm not too worried about sucking in too much dust. I'm really just hoping to restore a little of the natural airflow across the fins of the sink that I'm blocking with all that stuff crammed into the case.

 

I guess I should have asked up front - has anyone with a 1200xl that has a lot of internal mods experienced problems with overheating, or am I just being paranoid?

 

My fear probably goes back to my 320xe days, when I had to point a little desk fan at my case to keep it from freezing. And later, my 1meg 520st (again, piggybacked chips) that was *constantly* freezing unless I kept the top cover off...

[classics]

One of the original voltage regulators in the 1200XL will often die right after new components are added, but no, no problems with over heating.

 

Steve

[cephallus]

One of the original voltage regulators in the 1200XL will often die right after new components are added, but no, no problems with over heating.

 

Steve

 

Hmmm, something to add to the next Jameco order...thanks for the heads-up!

[+bob1200xl]

Yes. So does mine - if I read it carefully. C40 feeds Chips, C41 feeds memory.

 

In answer to the question of overheating: I have mounted a 3 1/2 inch hard drive in a 1200XL and it didn't get too hot. Of course, I pulled all the power supply components and used an external supply so that may not be a sufficient test. It would have to get pretty hot for it to lock up... like melted plastic.

 

 

Bob

 

 

 

At any rate, I'd take it from C40, which feeds memory rather than C41, which feeds the Big Chips.

 

My schematic shows it the other way, with C41 feeding memory (+5B).