braner@batcomputer.TN.CORNELL.EDU (braner) (08/20/86)
[]
An Atari dealer has kindly shown me a note from Atari, explaining
how to fix the high-pitched whine the 1040 makes. More on that
in the next posting. Here I want to report on some other hardware
related things I found when I finally opened the box, and a story
about lightning, with a moral.
I have an Atari 1040STf, and the mother board says "revision B".
It was shipped in April, 1986.
A few days ago I left home, and unplugged the computer system from
the power lines as usual. But the computer was still connected to
the phone line, through the modem. I came back after some heavy
thunderstorms, and the modem was dead. Investigation revealed that
the computer itself was also damaged: the 1488 chip that drives the
RS232 output was blown, and inflicted 12 volts on the mammoth 68901
MFP chip that drives it, a 5V device. Luckily, the MFP is OK.
The moral of the story: Put surge suppressors on the phone line,
and unplug that line too in inclement weather.
What I also found inside the box:
The CPU and RAM chips are NOT socketed. Only the ROMs are.
There is no socket for the (future) graphics chip, and only about
a half-inch space above the CPU (and under the metal shield)
for piggy-backing (and heat dispersion). (I have used my unmodified
1040 for hours on end (with the disk drive mostly idle) in 95 degrees
Farenheit, with no ill effects. To be extra safe, I _have_ later
installed a very small fan above the middle of the grating area on top,
blowing _up_. It is very effective. I use it only when the weather
is very hot.)
In the middle of the back area, between the disk drive and the power
supply module, there is an empty spot about 3 inches square. It was
clearly intended for the RF modulator, and some enterprising soul
could market a modulator to plug in there! (There is a hole in the metal
shield (but not the plastic case) for the RF connector, and a row of
holes in the PCB in the "south" end of the area). I am still mad at
Atari for promising the modulator and then backing out. Could the reason
be heat? RF emissions? Cynical marketing policies?
There is hope for those who wanted a composite video output, though:
in the same space intended for the modulator, there are traces in the
PCB, plus markings such as "R110", for 4 resistors, one capacitor and
one transistor. It seems to be for an emitter-follower buffer, with both
input and output connected to the video-jack area. Maybe somebody reading
this can tell us what it does, and the values of the components (by reverse
engineering or by an unbelievable act of corporate openness :-).
(Somebody told me that an MC1374 chip can be used to convert RGB to
composite. Experts: any comments?)
If you don't install a modulator inside, the space may be useful for
other add-ins (a FP coprocessor is my favorite dream). Unfortunately,
the space is sliced horizontally by the metal shield, so that there is
little more than a half-inch above and the same below.
Now a plea: Does anybody know where I can obtain the National Semiconducters
FP chip, the 32081? Price? Documentation? (This chip HAS been used with
the 68000, namely by Digital Acoustics, in their "Dtack grounded" add-on
boards for Apple ]['s.) (Alternatively, we may have to wait for the "TT",
but when? How many $$?) (The 68000-32081 combo is not that much slower
than the 68020-68881 (or the VAX...) (I only count orders of magnitude),
and should be much cheaper (?). The only real advantage of the TT will be
the possibility of running the 68020 (number crunching) and the 68000
(I/O) _simultaneously_.)
Another plea, to Megamax (I wrote them twice but no answer): Does the
source code offer (for $50) include the FP (assembly-language) source?
- Moshe Braner
Corson Hall, Cornell University, Ithaca NY 14853
(607) 272-3487
For electronic mail, my address is:
braner@amvax.tn.cornell.edu (ARPANET)
braner%amvax.tn.cornell.edu@WISCVM.BITNET (Bitnet)
{decvax,ihnp4,cmcl2,vax135}!cornell!amvax!braner (USENET) milo@ndmath.uucp (Greg Corson) (08/23/86)
A warning to those who would put surge suppressors on their phone lines...it is VERY important that those suppressors be placed at the point where the phone line enters the house (or as close as possible). Remember that surge suppressors work by presenting a dead short to high voltage pulses...phone wire is relatively high resistance stuff (compared to zip cord) and can get VERY hot if a high voltage surge goes down it and is shunted to ground. I saw some pictures in EDN magazine showing what happened to someone who had these suppressors on his phone line...he took a lightening hit and the phone cords leading to his modem (with surge protector) got so hot they left black scortch marks in his rug! Phone lines without the protectors didn't get hot at all. It probably takes a fairly close lightening hit to do this...but not a direct hit (nothing else in the guy's house was damaged). So if you install a surge protector...install it on the terminal block where the phone line comes into your house...better safe than sorry. Greg Corson pur-ee!iuvax!kangaro!milo P.S. I have 5 (yes F I V E) modems in my house...we have dual surge protection installed for free by the phone company. Carbon point arrestors on the pole and gas point ones on the service pannel in the house. I have never had any problem with lightening. P.S.S. Why 5 phone lines...I run a multi-line BBS system (219) 277-5825