Changing heatsinks

[lorddef]

Most people say I have a photographic memory, it would help if I could have remembered the useless crap that I needed for some of my final exams, but I think beer deleted all that, oh well.

[Karlos]

:lol: It seems I used to have one but the last few years have seen it reduced to sieve like powers of retention ;-)

[lorddef]

Hmm, a resistor should do the trick okay in this case.  Remember that you only want to loose 7 volts not 12 too  when you work out what resistor to use ;-)

[Karlos]

Well, V/I = R. In this case my fan is rated at 5V, 0.14A

So 7/.14 = 50 Ohms? Seems pretty low. The closest youd get is what, 47 Ohm resistor?

[Brian]

Ehm... resistors ain't a good option to lower V. Sure it does the trick but for it to work it creates heat. For shorter intervalls it'll work but when you're driving a motor for longer intervalls as with the fan you will most likely burn the resistor (something you don't want to happen while the machine is rendering stuff while you're asleep).

Best option is to find 5V on the card or take it from the motherboard.

[Karlos]

Brian wrote:
Ehm... resistors ain't a good option to lower V. Sure it does the trick but for it to work it creates heat. For shorter intervalls it'll work but when you're driving a motor for longer intervalls as with the fan you will most likely burn the resistor

Yeah, that's what I was thinking when I worked out the resistance and it came out so low - I can imagine a lot of heat dissipation for 50Ohm...

[lorddef]

Hmm, Brian has a good point, with this in mind maybe you should pull out your multimeter and source 5v from the board.  You may want to slap a diode in there too to stop any back emf.

[Karlos]

Well, the new cooling is working fine and much quiter. The card is still knackered though :lol:

[Karlos]

Wow, my card seems to be a prototype :-o

The rom is socketed (this is where the problems lay. I was just working on it and the label started to peel off the rom chip. Lo and behold, it is an UV erasable kind!

Man, that sure explains a lot :-)

Anyhow. a moment ago I got it to configure, saw that it was working from the early startup.

Things are looking up :-)

-edit-

Famous last words :lol:

Dead again!

[lorddef]

"Lo and behold, it is an UV erasable kind!"

I've pulled this type of EPROM from PC's before so I'm not sure if this makes it a prototype.

"Famous last words"

lol

[Karlos]

Well, it's up and running again....

I just played AB3D on it for a good 40 mins. Nostalgia overload there.

What I need to do is to desolder the socket and mount the chip directly. A couple of legs are half missing :-)

The problem is that the bloody solder contacts are minute. I get the sense that I will doubtless knack it up...

[lorddef]

Be very carefull not to get the tracks too hot, I've taken tracks off in seconds before by having my soldering iron turned up too high and keeping it on thew board for too long.

Is it a DIL socket?

[Karlos]

Yeah, it is.

The problem is that the socket adds 5mm to the height which causes the ROM chip to be pressed against the top of the SIMM when inserted. This is what has caused the gradual mechanical damage over time.

Without the socket, thered be ample space. I noticed that later revisions of the card all had the ROM directly mounted on the card.

[lorddef]

Shouldn't be too big a deal then, but I'm not the one holding the soldering iron  :-P

[Karlos]

Like I said, the solder junctions are tiny and the tracks are really, really thin. I'm not totally convinced I can remove it without damaging it beyond repair.

Just now it's working, but I know that if I just so much as look at it in a funny way, its going to spit the dummy on me again.

Funny, until yesterday I wouldn't have cared about it. Now that I have a use for it, I'm a bit more cautious :-)

[Dietmar]

>I can imagine a lot of heat dissipation for 50Ohm...

Not really. Look on the fan, it should have a label with the technical data. Small 12V 40mm fans are rated 1W or a bit above. Since you will be burning only a fraction of that in the resistor (50%?) and the rest in the fan, no problem with heat. Just get a 1W resistor for 10 cent.