csc@watmath.UUCP (Jan Gray) (05/07/86)
I've had my ST for five months, been running with a homebrew 1 Mbyte upgrade for four, ROMs for one. On Sunday morning my power supply smelled burnt, and the ST was dead when I turned it on. Fortunately, when I tried a new power supply the machine was fine. It was an old, black, tall power supply (with cables running out of both ends). Question: I remember an article a few months back from someone whose old power supply failed, and mention of some acknowledgement of the problem by Atari. Is there an official line from Atari? (Probably "yes, you overheated your power supply with the extra RAM, you lose!") Question: Has this happened to many of you? What did you do? "I knew things would start to fail once the warranty expired" Jan Gray
turner@imagen.UUCP (05/12/86)
> Question: I remember an article a few months back from someone whose old > power supply failed, and mention of some acknowledgement of the problem > by Atari. Is there an official line from Atari? (Probably "yes, you > overheated your power supply with the extra RAM, you lose!") > > Question: Has this happened to many of you? What did you do? > > "I knew things would start to fail once the warranty expired" > > Jan Gray *** REPLACE THIS LINE WITH YOUR MESSAGE *** i lost 3 (count them 3) ST's before i got wise and got a new power supply (both cables at one end) since then no hardware problems -- ---- "If only you could see what I've seen with your eyes" -Blade Runner Name: James M. Turner (not the James M. Turner at Lisp Machine Inc.) Mail: Imagen Corp. 2650 San Tomas Expressway, P.O. Box 58101 Santa Clara, CA 95052-8101 AT&T: (408) 986-9400 UUCP: ...{decvax,ucbvax}!decwrl!imagen!turner CompuServe: 76327,1575 GEnie : D-ARCANGEL
knnngt@ukma.UUCP (Alan Kennington) (05/13/86)
Yes, there is an official line. At least, I got a line from an Atari
hardware person. He told me that a check had been made and that this
showed that the problems were very rare. The story I heard from a non-Atari
individual last year was that 50% of supplies before September last year
(ie produced before that time) were faulty to the extent of emitting smoke
and giving a 15V difference between pins 1 and 7 on the supply instead of
5V. (Also giving a 35 mS pulse on boot-up.) But now the problems seem to be of
three kinds:
(1) Too much voltage on the 5V line.
(2) Too much smoke from the "brick".
(3) Blowing the MMU when extra RAM is added.
Now the question may be asked whether these are mutually exlusive, or
independent etc. My old supply had (1) but no (2). And I never tried (3).
The hardware person became merely sympathetic when I told him
that the warranty had expired. But it was the TOS ROMs that made
the problem evident, and they weren't available until it was too late.
The thing I don't understand is why it took a week of using the TOS ROMs
before one of these chips blew. Yet more mystery! If only this net
had an automatic voting capability to indicate whether people had
options (1), (2) or (3)!!
So long, Alan Kennington.gordon@sage.cs.reading.Ac.Uk (Simon Gordon) (05/17/86)
In article <3408@ukma.UUCP> knnngt@ukma.UUCP (Alan Kennington) writes: > > >But now the problems seem to be of >three kinds: >(1) Too much voltage on the 5V line. >(2) Too much smoke from the "brick". >(3) Blowing the MMU when extra RAM is added. >Now the question may be asked whether these are mutually exlusive, or >independent etc. My old supply had (1) but no (2). And I never tried (3). > So long, Alan Kennington. I have made a reply elsewhere with respect to this, but this article prompted me further. Why did your computer not blow at first ? This is simple. If a component is being driven too hard (the extra power drawn by extra roms) then, it may cope apparently ok for a bit before the extra stress on the component forces it to pack up. My first ST was purchased last september. At Xmas it packed up - it was working ok, I turned it off, had lunc, turned it back on and it just came up blank. Silica Shop (the major british supplier) replaced it (after a bit of a tussle). (just the keyboard that is) In april I had the 1 meg ram upgrade done for me (with the resisters) and roms finished. My machine is still ok despite the power supply being the origanal september one and my machine having to stand being moved to and from university often on a motorcycle. One interesting point was that the replacement (and it was definately not MY one repaired) had obviously been 'fiddled' with as the people that did the ram upgrade said that a couple of the ram chips on the board had been replaced and some chips had been resoldered. Sujesting it was a blown and repairred replacement - even though they sent it out with a new set of manuals, disks, and mouse (so I have two sets of these) Odd. From Simon Gordon @ Sibly Hall , Reading , UK
jhs@disunix.UUCP (05/22/86)
One point that may clear up some confusion. When you hang too much load on
a circuit like the MMU, this does at least three things:
1. It causes a DROP in the voltage at the load.
2. It causes more current to flow through the source device, even though
each individual load device may draw a slightly reduced current.
3. It causes an INCREASE in the voltage drop ACROSS COMPONENTS INSIDE THE
MMU, and thus an increase in power dissipation there.
What is especially damaging is when the driving circuit (MMU in this case) is
so overworked that it goes out of "saturated mode", in which the voltage drop
inside the switching transistors is very low, and into a "linear" mode in
which substantial voltages can develop, say, across base-collector junctions.
Substantial may mean 2 or 3 volts instead of the normal 0.2 or so. Multiply
this by a 2x increase in current, and you can see why something might fail.
I haven't investigated the ST upgrade problem, and in fact don't own an ST
yet, but I suspect this is what is going on.
-John Sangster
jhs@mitre-bedford.arpa