Mar 87 Letters
Volume Number: 3
Issue Number: 3
Column Tag: Letters
Those of you who have been around in the Computer field for a while will
recognize the name of Loy Spurlock, contemporary of Dan Paymar (Lower Case Adaptor
for Apple II), Randy Hyde (Lisa Assembler) and Dave Gordon (Programma
International & DataMost), from the early Apple II days. Loy started Computer Forum
in Santa Fe Springs and presently owns a service company in La Mirada called
Computer Quick which installs Levco’s MonsterMac. What makes Loy’s company unique
is that they actually scope out dead Macs to find out what killed them, rather than just
do board swaps. From this perspective, Loy tells us the truth about the Mac power
supply problem. -Ed.
Macintosh Power Supply failures
Loy Spurlock, President
Computer Quick, inc.
La Mirada, CA
The Macintosh power supply has been getting a bad rap lately. I have seen articles
written by “writers” claiming that the power supply is no good. The only reason those
articles ever saw print was simply because they were written by a writer who
normally writes for the magazine, not because they knew what they were talking about.
The problem is, these authors don’t know from Adam how the power supply
works, what goes bad, or anything else about them --or they wouldn’t have written the
article.
This whole hullaballoo reminds me of the same thing that happened with the Apple
II switching power supply. The Apple II, much the same as the Mac is now, was a leader
in the use of new technology. Up until the Apple II, computers were generally powered
with the older transformer type power supplies.
Anyway, at one point, there was a barrage of articles written about the problems
with Apple’s switching power supply --one such article was called, “A Worm in the
Apple.” All the “Authors” were bemoaning the fact that it was a switching power
supply. If only it were frame transformer, everything would be all right.
My guess is that when something is wrong, people are usually ready to throw the
blame onto whatever is new. Since switchers were new to micros, that technology took
the rap, rather than the amount of current it was designed for.
In actuality, the power supply was designed to produce a certain amount of
current at each of the various voltages. If Apple had used a standard transformer type
power supply of the same currents, the problem these authors were writing about
would still be there, but they would be writing about an under powered power supply
instead of the weaknesses of a switcher. Also, if Apple had designed their switcher to
produce more current, there wouldn’t have been an imagined deficiency, and the
Author would never have written the articles in the first place. More about designed
current levels later.
Why, then, did Apple not use a more powerful power supply to start with? At that
time--and still today to a lesser degree--switching power supplies cost more than
transformers. A transformer with twice the power could be purchased for half the
money of the switcher. Why, then, did Apple sacrifice power and money just to have a
switcher. Switchers have definite advantages, one being that they act like circuit
breakers when something goes wrong. For example, if you drop a pin on circuit board
and short something out, the switcher will switch off, rather than continuing to
produce current and fry the circuits on the board.
Clearly, Apple was ahead of its time. Apple was right, the Authors were wrong.
Today, switchers abound in high tech electronics. You can get switching power supplies
in a variety of voltages and currents. If the switcher had been so bad, they would not
have grown to such prominence.
Now, on to the Mac power supply. Is it weak? Was it designed poorly? In both
cases, the answer is the same; maybe, but not for the reasons cited by the authors in
the trade press. Let’s take the scenario from the top and analyze why these authors
think the way they do, and why they are wrong.
Jim (fictitious) Johnson is hammering away at the keyboard one Sunday
afternoon, trying to beat a Monday morning deadline, and smoke starts bellowing from
the top left vents of his Mac. With a panic snap of the wrist, he reaches behind the
smoking gun and flips the switch off. “Nuts,” he mumbles, “I’ll have to drag out the
old Radio Shack TRS80 to do this article”.
Monday morning; he turns in his ragged TRS80 printout and drags his Mac to the
local Apple dealer. Right now, this very moment, given all these circumstances, this
usually objective writer is in a very rotten mood. It won’t take much to set off his
short fuse. Then the word comes from the repair tech, “It was your power supply,” he
gleefully says with dollar signs in his eyes, “we replace more of these than any other
thing in the Mac. It happens all the time.”
Now, you (you the reader of this article) are probably mumbling to yourself,
“I’ll bet this really doesn’t happen, Loy’s just made up a story to put his point
across.” I’ve got news for you buster. It happens all the time.
Most local Apple dealer’s have a service department to --what else?-- provide
service for Apple products. They have this service department for three reasons; 1)
Apple likes them to have it, 2) It is a necessary evil to selling systems (when a
prospective buyer asks where he will get his $10,000 system serviced, the sales
person only has to point to the service window.), and 3) It does make a few (sometimes
a lot of) extra bucks.
In this service department, they usually have a service tech. However, because of
the way Apple provides service support to them, they don’t really have to know very
much. The Mac is made up of a motherboard (digital logic board- the part that does all
the computing), the internal disk drive, the infamous power supply board, the video
tube, and a variety of cables for connecting everything together.
All the tech has to do to diagnose your Mac is swap the motherboard. If the
computer works, it was the motherboard. If not, swap the power supply. If it then
works, it was the power supply--and so on.
When he finds that the power supply was the culprit, he gleefully tells you so and
collects your money.
After you’re gone, he packages up your old power supply and ships it to Apple.
Apple then has it repaired and ships it back to the computer store to be placed in yet
another poor soul’s Mac.
Ok, here’s the rub. This so called “power supply” board is more than just a
power supply. It consists of the power supply and the video circuitry. That’s right,