ostroff@oswego.UUCP (Boyd Ostroff ) (06/16/87)
I use a Mac 512Ke with Apple HD20 at home and with the recent warm weather
it has developed a high-frequency (15-20 khz) "whine" after it has been
on for awhile. It only seems to happen on warm (over 75 degree) days
after the computer has heated up.
The computer is about 18 months old and for the last 6 months has been on
24 hrs a day as a BBS. This is the first time I have had any hardware
problems at all.
I've read a lot about power supply failures and I'm wondering if this is
a prelude to a breakdown (I remember having a b/w tv years ago that did
this for awhile before the flyback transformer went up in smoke...).
So far this condition hasn't affected performance in any noticeable way,
but I find the noise so irritating that I have to shut the system down
in order to stay in the same room. I'm also getting reluctant to leave it
on when I'm not at home for fear of finding charred remains when I return...
Anybody have a similar experience? I don't have a fan - should I? Would
this cure it or just postpone the inevitable? I don't have Applecare,
so what kind of potential repair bill am I looking at? Any responses
would be greatly appreciated!
--
UUCP: seismo!rochester!rocksvax!oswego!ostroff
US MAIL: Boyd Ostroff, Technical Director, Department of Theatre
SUNY College at Oswego, Oswego, NY 13126
PHONE: (315) 341-2138chuq@plaid.UUCP (06/16/87)
>I use a Mac 512Ke with Apple HD20 at home and with the recent warm weather >it has developed a high-frequency (15-20 khz) "whine" after it has been >on for awhile. It only seems to happen on warm (over 75 degree) days >after the computer has heated up. > >I've read a lot about power supply failures and I'm wondering if this is >a prelude to a breakdown (I remember having a b/w tv years ago that did >this for awhile before the flyback transformer went up in smoke...). Actually, the power supply rarely fails (for details, read MacTutor). But it sounds like your flyback is getting marginal (the flyback happens to be attached to the analog board, which happens to be where the power supply is, which is why the board swappers call it a power supply failure -- never trust a man who believes that board swapping is a repair to give you technical information). I've had two flybacks fail on one of my Macs, the early boards used one that tended to break down under heat and short. >So far this condition hasn't affected performance in any noticeable way, >but I find the noise so irritating that I have to shut the system down >in order to stay in the same room. I'm also getting reluctant to leave it >on when I'm not at home for fear of finding charred remains when I return... Yes, I'd probably find a good repair depot (look at MacTutor for a place that repairs boards, not swaps them). The first time my Mac died, it cost me lots for a board swap. The second time my Mac died, it cost me $40 for a new flyback. It's been solid since then. Of course my second Mac seems to have a cold solder on the video, but I'm going to take a look at that in a week or so when my memory upgrade shows up. For details on Mac's and cold solder joints, read MacTutor... >Anybody have a similar experience? I don't have a fan - should I? Would >this cure it or just postpone the inevitable? You want a fan. All Mac Users, read my lips. YOU WANT A FAN. Sticking a fan on your Mac can drop the internal temperature significantly. While the Mac may be within spec (if you've put anything INSIDE the box, however, it isn't) it is at the high end of the spec. Lowering the temperature reduces the stress on the components, which can only make them better and more reliable. I use the Kensington, which moves the powerswitch up front (which is good, because I use enclosed computer desks) and also has a surge supressor. But any fan is better than no fan. chuq Chuq Von Rospach chuq@sun.COM Delphi: CHUQ Now, where did my ex-wife put my Fairy Dust?
briand@tekig4.UUCP (06/16/87)
>I use a Mac 512Ke with Apple HD20 at home and with the recent warm weather >it has developed a high-frequency (15-20 khz) "whine" after it has been >on for awhile. It only seems to happen on warm (over 75 degree) days >after the computer has heated up. > >I've read a lot about power supply failures and I'm wondering if this is >a prelude to a breakdown (I remember having a b/w tv years ago that did >this for awhile before the flyback transformer went up in smoke...). This all depends upon how sensitive your ears are at 15.5kHz :-) Very probably all that is happening is that expansion is allowing components in the flyback transformer to vibrate sympathetically. I've seen Macs that are noisy straight out of the box, I had one that only made a low whine after it warmed up for 30 minutes, and most are pretty silent. I have never heard one so loud it sent me out of the room, but I've heard them annoying enough to cause people to hold conversations elsewhere. The way I've fixed a few of these is to stick toothpicks into the frame of the flyback transformer wherever vibrations might start. For example, there is often a frame wire around the ferrite core material, to physically hold the core together. Sticking a toothpick between the frame wire and the core ferrite in a few places (breaking off the unneeded end) seems to fix these right up. Apparently the wood, being a flexible material, can absorb these vibrations. You don't need to jam these in super-tight: if you're worried about breaking something don't do it. Also, putting RTV Silastic around the same locations can dampen the vibrations. This is the vaseline-like goop they use to conduct heat between transistors and their heat sinks: it conducts heat but is highly dielectric. I would warn you to unplug the Mac and completely discharge the high-voltage section before doing any of this, or you may find a new meaning of the Mac term "alert!" Also, though I think this is a good thing to try first, I won't be held responsible if your board later burns up - it could be that this is simply not the problem. As for how much you're looking at to repair, call your dealer and ask how much a standard video board replacement costs. If it's too much, you might consider buying AppleCare before you need it. I believe, but I don't know, that the dealer's cost for a video board swap kit is about $80 - can anyone correct me? -- -Brian Diehm (SDA - Standard Disclaimers Apply) Tektronix, Inc. briand@tekig4.TEK.COM or {decvax,cae780,uw-beaver}!tektronix!tekig4!briand
gnome@oliveb.UUCP (06/17/87)
in article <403@oswego.UUCP>, ostroff@oswego.UUCP (Boyd Ostroff ) says: > > I use a Mac 512Ke with Apple HD20 at home and with the recent warm weather > it has developed a high-frequency (15-20 khz) "whine" after it has been > on for awhile. It only seems to happen on warm (over 75 degree) days > after the computer has heated up. Well, it would be nice if you could narrow it down to either the analog board or the HDU. If it is the HDU, it's probably the infamous "squealing grounding button" effect that causes the hard drive to squeal constantly until someome goes crazy and disables it with a hammer. Generally the grounding button, which resides at the center of the HDU platter motor, isn't really needed and can be removed. If it's your power supply, well, I'd recommend putting a fan on your machine and, if you have access to someone, get a hardware person to "reseat" the DC power cable connectors and test/tweek the supply voltage to make sure it's within range. Good luck, Gary "Unhappy MacNam..." -Bozos
gnome@oliveb.UUCP (Gary) (06/17/87)
in article <21199@sun.uucp>, chuq%plaid@Sun.COM (Chuq Von Rospach) says: > Posted: Tue Jun 16 09:46:00 1987 > You want a fan. All Mac Users, read my lips. YOU WANT A FAN. Sticking a > fan on your Mac can drop the internal temperature significantly. While the > Mac may be within spec (if you've put anything INSIDE the box, however, it > isn't) it is at the high end of the spec. Lowering the temperature reduces > the stress on the components, which can only make them better and more > reliable. I use the Kensington, which moves the powerswitch up front (which > is good, because I use enclosed computer desks) and also has a surge > supressor. But any fan is better than no fan. > Chuq Von Rospach chuq@sun.COM Delphi: CHUQ I'll second that! Imagine how hot the side and vent area feels, then imagine how hot the components have to be to get the enclosure that hot, then imagine how hot the junctions in the chips/power components have to be. When you figure in the junction/case temperature differential, the numbers get real hot really fast. Even though the amount of dust inside the case increases, the reduced failure rate of the power/video circuitry more than offsets the cost of the fan. By the way, I also think the Kensington is neat because I like my machine to have a Mohawk! Gary
ostroff@oswego.UUCP (Boyd Ostroff ) (06/29/87)
About two weeks ago I posted an an article requesting advice on a high-
pitched "whine" my 512Ke mac was emitting. I suspected the culprit was
the flyback transformer. As of this date, I've added a (Kensington)
fan which has stopped the noise. I also have the computer in an air-
conditioned room now, which is better than some of the 80+ degree days
it was being subjected to before.
The bbs has been running continuously on my mac for the last 96 hours
and there is no hint of trouble yet. As a subjective opinion, though, the
upper left-hand side of the case feels warmer to the touch than similar
fan-equipped macs at work.
Thanks to everyone on the net who responded with suggestions and war
stories. If my analog board flames out, I will post...
BTW, the bulletin board, known as "The CallBoard", exists for the purpose of
exchanging information on employment opportunities and other topics of
interest in the Performing Arts. There is no charge for using the system.
If you know of anyone interested, please contact me at the address below.
-Boyd
--
UUCP: seismo!rochester!rocksvax!oswego!ostroff
US MAIL: Boyd Ostroff, Technical Director, Department of Theatre
SUNY College at Oswego, Oswego, NY 13126
PHONE: (315) 341-2138