Date: Thu, 17 Nov 2005 10:50:06 +1300 From: Richard Halkyard <[EMAIL PROTECTED]>
I've recently acquired a PowerMac 6100 with the DOS card installed, and it seems to be acting up. It has a fresh PRAM battery, but will sometimes act as if there is no battery (startup chime but no display), and then act fine with no data loss later. When it is running, it will occasionally lock up, with coloured pixels randomly flashing in the top-left of the display. I've tried swapping and removing all the bits and pieces - DOS card, cache, RAM, hard disk, CD and everything. Its driving me nuts, because I rather liked the idea of having an (old) PC and Mac in one. Any ideas?
I've seen similar symptoms in several 7100s and the cause is overheating of the CPU chip. In those cases, the CPU chip was overheating because the heat sink grease had dried out and was no longer doing its job.
It's not a certain diagnoses for you, but it's fairly easy to test and will only cost you $2 - $3 and a trip to Radio Shack if you don't already have some heat sink grease on hand.
Remove the motherboard from the machine. Carefully unclip the heat sink (push the tabs out from the back of the board). I write, "carefully", because putting undue downward pressure on the heat sink has been known to *crack* the CPU in several cases.
There will be a white residue on the CPU and on the heat sink. Originally this stuff should have been nice and creamy. At this point it is probably dry and powdery. Gently clean it off using rubbing alcohol (70% isopropyl) or 90% isopropyl and some kind of swab. In a pinch Q-tips or cotton balls are okay if you're careful not to leave little polyester fibers everywhere. Clean it off of both surfaces. Let them dry.
Heat Sink grease is available from Radio Shack for $2 - $3. It comes in a little blue and white tube on a card which is usually hanging on a peg board. Sure, you can spend $15 on Arctic Silver, but the RS stuff does the job well enough.
Apple a little dab on the square metal die in the center of CPU. Do not overapply. Heat Sink grease is mildly electrically conductive and if it runs off of the chip onto the pins of the CPU it can cause shorts. I killed a Power120 that way once. The grease just needs to fill the tiny spaces caused by the CPU die and the heat sink not being perfectly flat surfaces.
Carefully clip the heat sink back into place. Try not to slide it from side to side when installing it. Shoot for a straight approach to the CPU without a lot of side to side sliding. Coming in with the heat sink angled a bit, so that two clips go into their holes before rotating the heat sink down so that the other two clips hit their holes often works well.
Resinstall your motherboard and test it out. You may also wish to consider installing a little fan on the heat sink. The fans typically bolted to 80486 heat sinks could be unscrewed and fit nicely in the center of the x100 heat sink. Use small cable ties (also available at Radio Shack) to secure the fan to the heat sink tentacles through the fan's screw holes--i.e. the cable ties go through the fan's screw holes and around one of the arms of the heat sink. You can suspend the fan just above the flat heat sink surface this way.
Date: Wed, 16 Nov 2005 22:00:52 -0800 From: "Matthew S. Carpenter" <[EMAIL PROTECTED]>
I tried to grab it but still ended up dropping it about a foot... Anyway when I brought it to the lab upstairs I couldn't get the damn thing to glitch out...Gad, it made me look like an ass.
Probably jolted the heat sink about just enough to make better contact with the CPU. Perhaps rubbed some of the powder into a better position.
Jeff Walther -- 1st-PowerMacs is sponsored by <http://lowendmac.com/> and... Small Dog Electronics http://www.smalldog.com | Refurbished Drives | -- Sonnet & PowerLogix Upgrades - start at $169 | & CDRWs on Sale! | Support Low End Mac <http://lowendmac.com/lists/support.html> 1st PowerMacs list info: <http://lowendmac.com/lists/1st-powermacs.shtml> --> AOL users, remove "mailto:"; Send list messages to: <mailto:1st-powermacs@mail.maclaunch.com> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> List archive: <http://mail.maclaunch.com/lists/1st-powermacs/> --------------------------------------------------------------- iPod Accessories for Less at 1-800-iPOD.COM Fast Delivery, Low Price, Good Deal www.1800ipod.com ---------------------------------------------------------------
