donch@tekirl.TEK.COM (Don Chitwood) (09/09/87)
My personal Mac at home has developed a rhythmic ticking, roughly a 1 second cycle. I opened the case yesterday and used a plastic stethoscope to home in on the sound. It was coming from the transformer on the power supply board (the one mounted fairly low, and probably the main supply transformer.) Up close, I could discern the ticking to be more complex than I thought. It was like a 1 sec and a 1.2 second cycle superimposed on each other. They would phase in and out of synch in a repeatable manner. I also discovered the sound was carried by the speaker (earphones made that real clear), but was primarily coming from the tranny. All solder joints on the board looked great, no signs of overheating anywhere. Anyone know if this is a problem of concern, i.e. is a power-board imolation imminent? If so, can I get a replacement transformer from apple? If not, where is a replacement available? Thanks in advance for any advice. Don Chitwood Tektronix, Inc.
jccf@ihlpg.ATT.COM (Hartong) (09/10/87)
In article <740@tekirl.TEK.COM>, donch@tekirl.TEK.COM (Don Chitwood) writes: > > My personal Mac at home has developed a rhythmic ticking, roughly a 1 second > cycle. I opened the case yesterday and used a plastic stethoscope to home > in on the sound. It was coming from the transformer on the power supply > board (the one mounted fairly low, and probably the main supply transformer. . . . > > Don Chitwood > Tektronix, Inc. Some time ago I found the same problem. Since my home mac is slightly different from the standard mac (It has a series stabilized PSU i.s.o. a concept with flyback transformer) the problem could be heard a bit better. After some investigation I found out that there were "dips" in the 12 volt Power Suply Line. When expirimenting with internal and external drives, Standard Sony and 3rd Party Drives the following conclusion came up: After Reset the power dips occured when a disk drive (Sony Only) was attached to the Mac, no matter if it was internal or external. With a 3rd Party drive (don't remember the brand anymore) these problems did not occur. This is because the mac is looking for a drive to use, and tries to select the internal or external drive, thus making the Enable line active. When the drive is running/spinning (Sony drive, further refferenced as "the drive") , no dips in the 12 V. line. (because the drive is selected continiously) When the system has started upp (i.e. system loaded) the problem still occurs, but may dissapear after some twiddling with the drive lines (CA0, CA1, CA2, Select, Enable ). This was done using a disk-drive diagnostic utility. The problem lies in the fact that every time the line Enable is activated a dip on the 12 volt line occurs. It seems that the 12v line is shortcutted for a very short time (+/- 1 ms). This results in a high current floating through the 12 volt line and has impact on the rest of the mac, wherefrom you hear the "click tik ticking". The frequency you described is the same as the one I noticed. This points probably to a faulty hardware dessign (interaction) of the IWM and Sony disk drives. Or the Sony drive takes to much current on being enabled. The ticking and power dips / high current peaks were verified by a friend who's working as a repairsman with a Apple dealer, and he found the same things, but not as sever as with my Mac 'cause the Mac's PSU can give a higher peak current on their 12 v The dips seem to have no further impact on a proper working mac. The extra power dissipation in the PSU due to this dips (high current) is probably minimal. Hope this helps (?) a bit. Piter Jonker, Hilversum, (A center Town of ) Holland. ihnp4!ihlpg!hvlpa!pjonker <--- Use this address when sending reply's The currently used one is a remote login.
gnome@oliveb.UUCP (Gary) (09/16/87)
> > > My personal Mac at home has developed a rhythmic ticking, roughly a 1 second > cycle. I opened the case yesterday and used a plastic stethoscope to home > in on the sound. It was coming from the transformer on the power supply > board (the one mounted fairly low, and probably the main supply transformer.) > Up close, I could discern the ticking to be more complex than I thought. > Don Chitwood From what I can tell, it is a problem with the power supply not handling intermittent load very well. The ticking will stop when the CPU is doing something very compute intensive. Basically, it's causing the power supply to respond to a series of non-repetitive pseudo-random increases in load while executing a normal program -- which is easier than trying to filter widely-spaced intense current pulses from the system (ie: the Ticking). I am thinking about tracking-down the major offending areas on the mother board and add some extra filtering (where there's room). It's not going to cause your transformer to die, but, as always, I strongly recommend putting a Kensington fan on your machine. It'll drop the inside temperature very well and is negligibly loud in comparison to most HDU's... Gary (hplabs,allegra,sun,amdahl)oliveb!oliven!gnome
wb1j+@andrew.cmu.edu (William M. Bumgarner) (11/06/88)
> sometimes I hear a ticking sound
so someone elses mac does it to...
If the room is really quiet, I can hear a faint clicking coming from my mac...
usually starts after disk access and sometimes stops/sometimes doesn't. Will
start at other times to.
Is my mac going to explode? Is it haunted? What is the deal?
just curios...
b.bumwerner@utastro.UUCP (Werner Uhrig) (11/06/88)
In article <IXQq6Iy00UgXI1mX5N@andrew.cmu.edu>, wb1j+@andrew.cmu.edu (William M. Bumgarner) writes: > > sometimes I hear a ticking sound > If the room is really quiet, I can hear a faint clicking coming from my mac... > Is my mac going to explode? Is it haunted? What is the deal? this ticking sound is associated with the voltage level. adjusting the voltage level on the analog board to just below ~5volts will take care of that... but no matter what you do, those boards tend to die with constant regularity... -- --------------------> PREFERED-RETURN-ADDRESS-FOLLOWS <--------------------- (ARPA) werner@rascal.ics.utexas.edu (Internet: 128.83.144.1) (INTERNET) werner%rascal.ics.utexas.edu@cs.utexas.edu (UUCP) ..!utastro!werner or ..!uunet!rascal.ics.utexas.edu!werner
wb1j+@andrew.cmu.edu (William M. Bumgarner) (11/07/88)
My Mac Plus is over 2 years old, and I have never had a power supply problem, and I'm running 2.5 megs (1 meg for a long time-- 256K chips take more power than 1 meg CMOS). Anyway-- So now I know how to get rid of the clicking;adjust the power supply to as close to 5 volts as possible, but WHAT is clicking? b.bum wb1j+@andrew.cmu.edu