Conference hydra::amiga_v1

2944.0. "Amiga Repair info from USENET" by TALLIS::MCAFEE (Steve McAfee) Thu Sep 21 1989 10:34

From: [email protected] (Erick Parsons)
Subject: Fix that baby!
Date: 18 Sep 89 21:54:11 GMT
 
I've noticed a lot of help me messages on the board lately and can sympathize
with the poor person that loses use of his machine due to a shortage of 
that magic smoke that holds silicon chips together soooo....
 
For those of you that don't have access to a descent BBS here is something
that I found on one of our local boards that looks VERY useful. I took this
file printed it out and filed it so's that if and when my beloved machine
should stop ticking I could fall back on this... Looks good to me :-)
 
--------------------------------cut here------------------------------
 
 
                             THE FLAKE REPORT
 
"Flaky" (July 15, 1989) Hacker's slang as meaning:
     1. Erratic and/or unpredictable behavior or experience
     2. Sometimes it works; sometimes it don't
     3. Primary cause of the following auditory spasms:
          a. "ARGH!!!!"
          b. "AH XXXX..."
          c. "#@&$!"
          d. "I need a career change; marketing!"
 
Usage: "He's getting FLAKY..."
Means: "RUN! HIDE!"
 
A Bruce's Repair quote:
"If it works; it won't."
 
Ok folks, I'm compiling a list of what has caused flaky operation of the
Amiga computers. This is a very unpopular subject with Amiga worshippers,
but it should be one to pay particular attention since it can harm any
product faster than obsolescence and DOES cause untold user-hours of
frustrations. Flakiness affects everyone and everything from product
development to end-users and especially service. If you can add some more
to this list, you can give me a call at (415) 525-6973 and ask for Bruce.
I'm busy most of the week so the best time is on Sundays in the morning. If
you don't mind listenning to a morning grouch call any other morning.
 
In particular is a problem of poorly designed, slow-to-access RAM boards.
This can be especially prominent with fast expansion devices like hard
drives and frame grabbers. Number one on the list of bad boards are all
those RAM boards with 150 nano-second RAMs. This is the time it takes the
RAM to access valid data. The smaller this number the better.
 
There are a lot of Amigas that need modifications. Starting with the
A1000's, the daughter board needs to have its PAL chips wired together to
the mother board ground and a wire to the expansion bus to the power supply
ground connector. In worst cases, two of the PAL chips must be replaced
with faster one's. The best source of PALs has been from Spirit
Technologies. The A2000's needed to have the keyboard data and clock line
capacitors removed. All the Eltek power supplies needed to be checked that
a .01 MFD capacitor was installed across R65 to suppress noise and a "00"
with a line through it written on the power supply label. The buffer chips
U605 and U602 should be 74ALS245 and not the slower 74LS245. A 3300 ohm
resistor should be installed between pin #20 and pin #11 on chip U605's
address strobe. The Gary chip has been fixed to allow processor access to
the KickRoms and expansion devices without needless co-processor
contention. (The MOS Gary) The A500 especially needed a piece of cardboard
placed behind the keyboard to prevent the keyboard from shorting to the
mother board metal shielding. An authorized transistor kludge must be
installed on all but the most recent A500's to clean up a signal from the
Gary chip. The biggest flake generator was and still is the metal shielding
on the A500. The main metal shielding had a lip just behind the internal
disk drive (i.e just left of the drive as you face the computer) which does
cause shorts at the end of the drive ribbon cable. The solution is to bend
the lip under the shielding or to put electrical tap over the edge of the
lip.
 
Much can be said about poorly written programs. We've all suffered as
unpaid and unwilling "beta testers" from companies lacking in product
quality. If it works on their machine, it does not necessarily mean that it
will work on all Amigas because of hardware, software, update, and user
differences. Sometimes they listen to the problems; sometimes they ignore
or pacify us with promises, good-will, and just pure charm. Worst case is
the buck passing. Badly written programs can go wild and corrupt our system
and even ruin DOS file structures. It can be as subtle as corrupting a
single bit, presently unused, to wiping out an entire system. Programs can
at times work with no apparent trouble until it's discovered later in time.
This can lead to blaming the wrong program or hardware as the cause of the
problems. This will sound very cynical but don't believe ANY review or even
this report of mine. (sigh..) Just take it with a grain of salt. Look over
people's shoulders, get the dealers to demonstrate their wares, stop by a
free-form users group and judge for yourself. Seek-out end-users of a
product. Get to know the modem community of Amiga users. Report problems to
the people responsible for the product if you think you've found a
consistent problem. Unfortunately, flaky problems are not easily repeatable
nor consistent, so it may be hard for them to justify their time to prove,
find, and solve the problem beyond a symptom.
 
Static electricity, even when we don't feel or hear the "tingle", can make
computer chips flaky. Always touch the power supply case before even
getting close to any circuit board or chip. In the situation of the A500,
touch the internal disk drive case. A lot of damage has been caused by
AGNUS chip installations. CBM has packaged the computer chips without
anti-static material and the retailer many times have not Xeroxed the
installation instructions for the customers. Topping the list of user
burn-outs is improper cable connections or installation. If you can't bet
your wallet, don't do it. I'd say a fair retailer AGNUS installation charge
should be around $20-$25.
 
Degrees of unfamiliarity with the equipment or the system can cause
unpredictable results. I shutter at the thought of what I would do to my
present system if I was a new user and not able to access all the books,
documentation, experience, and lastly my fellow computists. An old problem
with books, documentation, and advice is that a certain level of background
knowledge is expected and assumptions about your system are made from all
sides of communication. The learning process is a leap frogging of books,
notes, magazines, practice, and many times just pure inquisitive hands-on
hacking.
 
Never assume a computer cable is correct if it fits. There are unending
variations of cables with the same connectors on the ends. Once you've
found the purpose and correct cable, it's best to label the connector ends
with where they go. It's always good to have a continuity checker and
documentation of the pin assignments. The wrong cable can and does burnout
computers. Worst case is if it becomes flaky.
 
Ok, the following is are extracts from my notes and take it with a grain of
salt for flavoring. Be careful, because it is in a raw state and reaching a
conclusion from the notes will have to be tested for other machines.
 
UNSKILLED AND UNKNOWLEDGEABLE ATTEMPTS AT REPAIR OR MAINTENANCE CAN BE
EXTREMELY DANGEROUS AND SHOULD BE LEFT TO QUALIFIED TECHNICIANS ONLY.
UNAUTHORIZED SERVICE VOIDS YOUR WARRENTY.
 
 
All monitors
   1) Re-solder HV coil to main board
   2) Clean off dust and oil
   3) Check for burnt or heated spots
 
1084 monitor (very similar to 1902A)
   1) Intermittents
      a) Cold solder joints and broken traces especially around
      daughter boards and HV coil and leads
   2) VERY INTERMITTENT "snap!" of video; audibly noticeable.
 
1084S-Philips (very similar to 1902A)
   1) Nothing
      a) bad R475 (15K 2w flame) damaged from bad C476 (.047uF, 250V)
      and T402. Between June 88 and Sept 88 require warranty repair.
      1084S-P monitor repair kit PN# 314891-01 billed $44 and credited
      when T402 is returned to parts depot with NARDA form.
 
1902/2002 monitor
   1) Fuse blower
      a) defective degaussing switch (TH501)
      b) defective voltage regulator STR30123 (IC501)
 
A500
   1) no mouse movements
      a) replace burnt EMI401 (1.0 ohm 1/4 watt resistor)
   2) flaky computer
      a) do the 2N3906 kludge
      b) check main computer shield shorting behind disk drive
      c) Check solder joints on power socket
      d) flaky internal disk drive power cord
      e) check for bent chip pins and for bent connector pins
      f) check keyboard assembly for flakes
   3) Power Supply (PN 312503-05)
      a) pin1 +5V 4.5A
      b) pin2 shield gnd      __  __
      c) pin3 +12V 1A        |3 \/4 |
      d) pin4 signal gnd     |  5   | Looking into the plug end
      e) pin5 -12V .1A       |2___1_|
   4) Green Screen; 10 short 1 long power LED blink
      a) clean and re-insert Agnus chip
   5) flaky keyboard assembly with spurious characters or crash with
      CAPLOCK LED blink
      a) replace keyboard and tell customer of possiblity of a serial
      device being connected to the parallel connector
 
A1000
   1) fast steady power LED blink; dark screen
      a) 74S51 (U9I) & 74F74 (U8I); Damaged from expansion port
   2) no parallel output
      a) 8520
      b) PAULA
   3) Goes thru diagnostic blinks but no Kick icon
      a) Check for internal disk drive "track-zeroing" movement
   4) Dead
      a) check that expansion shield fingers aren't bent to mother
      board
   5) Check for bent connector pins
   6) no serial
      a) check MC1488 & MC1489
      b) check PAULA
   7) Bad mouse or joy stick movements
      a) check 74LS157
      b) check 8520's
 
A2000 (see also A500 & A1000 & A2500 for hints)
   1) Red screen; power LED blinks 9 short 1 long continuously
      a) bad ram with open
   2) Dark blank screen on power-up; LED dim
      a) BUSTER
   3) System time erratic
      a) check for noise on TICK line; CBM modification to power supply
   4) Bad mouse movements
      a) 8520
      b) clean mouse
      c) broken wires in mouse cord
      d) bad 74LS157 (U202)
   5) First character from keyboard missing after power-up
      a) cut out C910 & C911; CBM modification
   6) Fuzzy video
      a) remove a turn from the ferrite beads on the RGB lines
   7) White screen; no Workbench Icon; LED bright
      a) No power to PAULA; R200 (1 ohm resistor) burnt
   8) intermittent guru's
      a) Bad contacts on BridgeBoard (card edge or chips or bus-timing)
      b) Virus use KV and Sentry program
      c) Bad program(s)
      d) Bad ram expansion board with flaky 150ns ram (should be
      100ns);
      AMIGA 25000 (twenty-five thousand) 2MEG board is FLAKY
      e) use TestMem by Bruce's repair to find bad bits
      f) CHECK THE CLOCK SIGNALS with scope for proper voltage levels
   9) No Red in RGB only (new unit)
      a) bad solder joint or bad trace under board at RGB connector
   10) Check for bent connector pins
   11) No Serial Port
      a) DTR always on
         1) replace MC1488 &/| MC1489
         2) bad U301 CIA
         3) bad PAULA
   12) Modifications:
      a) Replace U602 and U605 (74LS245) with 74ALS245
         Make sure that 74XX24(4|5)'s between Agnus & Ram are F types
         the symptoms include spots appearing on screen
      b) Cut-out C910 and C911
      c) Put noise by-pass cap (.01ufd) on ElTek power supply TICK line
      across R65.
      d) Check for proper usage of ferrite beads at video connector
      e) put 3300 ohm resistor between #20 & #11 of U605
      f) Read TechTopics Issue #25 Section #3 (Apr-May-Jun 89) for details
         1) remove R901, C917, C902, C910, C911, C905, C908, C230, C240
         2) replace 1.2 KickRom with 1.3 or latest version
         3) if U205 & U206 are 74HC244 install RP904, RP905, RP906
         (4.7Kx5); if they are not DON'T install (e.g. 74HCT244)
         4) add .01 UFD cap on J300 center connector to ground pad
         5) add 470 ohm resistor to D800 cathode to second pad from the
         left, under CN605. 4.3 rev boards and up have R1000 left of Q302
         instead.
         6) if R5719 installed, add 470 ohm resistor between VCC and CPU
         side of R106.
         7) Replace ALL Gary chips (5719) with MOS type p.n. 318072-01
         8) Install new reset chip MITSUMI PST518B into ALL rev 6 boards
         (see TechTopics 25/3-3.1)
   13) Bad joy stick moves
      a) U202 (74LS157)
   14) Garbage from printer port
      a) bad U300 CIA
 
A2500 (see also A2000 for hints)
   1) Put 3.3k ohm pull-up resistors on pin 11, 12, 13, and 14 on U605
      These are buffered AS, UDS, LDS, and R/W signals for the
      expansion
 
A2XXX Power Supply
   1) check diodes and all semiconductors with digital IC-safe ohmmeter
   2) use variable transformer to bring AC voltage to operation
   3) use 25ohm 10 watt resistor on 5v+ main to load for testing
 
Amiga Disk Drives
   1) Clean with Q-tips and alcohol
      a) if heads are sticky when they touch each other, clean heads
      with "KESTER Rosin Residue Remover".
   2) "TICK-TICK" (5 ticks/sec noise with spinning disk in drive)
      a) after cleaning head and spindle, try lightening the pressure
      of the head spring (problem especially with #? drives)
   3) Works fine when connected as an Amiga Drive but not when
      connected to a PC Bridgeboard.
      a) Replace the 74LS38 with a 7438 chip.
   4) intermittent operation
      a) Broken wires in cable; check daughter board interconnects
      b) cracked magnetic glass switches
      c) Magnetic interference: rotate drive 90 degrees & recheck
      d) Motor spin erratic (on-off); re-solder motor board
         1) for Matsushita Drives, surface mount chip located between
         the drive frame and motor board and behind the eject button
         has bad contact; wedge with spacer
   5) Head "plays like a violin" on the disk
      a) clean head with rosin remover
   6) If a cardboard drive protector is used, check drive head mounts
      and angles. Advise user of the danger of using head protectors
      from another drive and the possibility of damage to heads with
      worn protectors bending the head mount springs.
   7) If dogs and cats are within fur range, blow into drive openning.
 
Hard Drive Controllers
   1) check voltages & cables
   2) check bus buffer chips
   3) check daughter board interconnects
 
A-Live Board (for A500)
   1) With time (hours and moon phase) D#aint## will be missing pixels
   from its picture when loaded; reloading the same picture with D#####
   will eventually bring back all the missing pixels!  This problem
   happens when the S#### Harddrive is connected between the A-Live and
   the A500. Other symptoms include the volume names to WorkBench
   Screen get corrupted but can be read with the INFO command without
   error!
    ) UNSOLVED MYSTERY!!
      a) Gary chip revision? (How do I get the latest version...)
      b) Power Supply voltage too low? Too high?
      c) Bus over-load?
      d) Needs bus termination?
      e) Needs F, ALS, or HC type chips buffering between video RAM &
         Agnus?
 
AMIGA RAM BOARDS
   1) A1000 Spirit board
      a) interconnects broken on Spirit Ram Board
      b) check for correct shorting blocks and wiring
   2) Remove and replace 150NS boards with faster ones.
   3) Use Bruce's TestMem to find bad chips
 
Amiga Repair paths:
   A) Get customer to relate what activity was occurring before
      the onset of the problem.
   B) Color of Screen and activity of LEDs
      1) Dark screen LED dead or blinking quickly
         a) Check power supply and TICK line
         b) Check ALL clocks
         c) Check power on each individual chip
 
Tips:
   1) Bad RAM with an internal OPEN circuit can be checked by
   "piggy-backing" the ram chip with the same type of RAM
   2) Bad RAM with an internal SHORT circuit can be hotter to the touch
   than the rest of the RAMs
   3) Improper removal of chips from sockets with a screwdriver can cut
   circuit traces under the chip; always check under chips and for
   damaged socket connections.
   5) For the A2000-A2500, put four 3.3K ohm pull up resistors on U605
   (74ALS245)
      a) pin11 to pin20; pin12 to pin20; pin13 to pin20; pin14 to pin20
 
Tips for Smooth Operation of the Amigas
by Bryce Nesbitt & Bruce Takahashi
 
(previously written a couple of years ago)
 
1) For the Amiga A1000, connect the pin #10's (ground) of the four PAL's
together on the daughter board with heavy wire.  Apparently the signal
ground path is strange and creates unreliable logic signals to U6J, U6K,
U6L, and U6N.  If you want a better connection, wire the mother board and
daughter board grounds together.
 
2) Check the expansion hold-down screws for proper length (not too long)
Sometimes the screw will bend and short the second of the two layers of
sheet metal to the circuit board. It may be best to try and first set the
screws without the video expansion ram to "pre-tap" the sheet metal. It
will be easier then to snug the hold-down screws for the expansion card.
 
3) Push all chips down fully into sockets.  Some chips may not be seated
properly or even have bent pins.  Straighten bent chip pins with a pair of
smooth pliers.
 
4) Preferences has a screen centering gadget that if moved too far to the
left, will cause some of the sprites to be distorted.
 
5) For programmers:
        a) Use this instead of AllocMem():
 
#include "exec/memory.h"
 
/* Safe AllocMem.  Will not let your run the system down to zero bytes.
 * For all to use, by Bryce Nesbitt
 *
 * You may wish to increase PANIC_FACTOR.
 */
#define PANIC_FACTOR_CHIP 4096L
 
APTR SafeAllocMem(size,flags)
long size;
long flags;
{
   register APTR p;
 
   if ( p=(APTR)AllocMem(size, flags) ) {
      if ( AvailMem(MEMF_CHIP) < PANIC_FACTOR_CHIP ) {
         FreeMem(p,size);
         return(0);
      } /* System is low... no go! */
   }
   return(p);
}
 
If you need to tell the user that the system is out of memory, but there
is not enough memory to post a requester or Alert, simply set the title of
your Window or Screen to "** NO MEMORY **" (possibly with a red pen
color). This operation does not require any allocations. b) There is a bug
in Text() that will clip text too soon if the write is started from beyond
the left edge of the RastPort. c) WindowToFront() (and probably the other
Intuition "deferred" actions) will lock up if the user is holding down an
icon from the Workbench tool.
 
6) If you use internal memory expansion, you should ground clip the
motherboard to the internal expansion board, preferably at the point on
the expansion were the ram array is.
 
7) Use only high quality disks. Poor disks may format and copy correctly
but time may find lost data or files.
 
8) Make sure that your machine's fan is unobstructed and operating
 
9) Use a single AC power outlet with enough grounded power sockets for all
your equipment.  This keeps the AC polarization correct between all your
equipment power supplies. If you examine a three prong outlet, you will
notice that it looks like a pair of eyes with a mouth.  The mouth is
supposed to be electrical "ground"; the smaller slot is the "hot"; the
larger slot is "neutral".  A power plug without a ground prong may have
one of its contact blades larger to fit only in the "neutral" slot. Don't
ever defeat it's purpose. To do so will endanger you and your equipment.
 
10) This should have been ICHI BAN: Never connect or disconnect cables
while equipment are powered, or blindly probe for a mating.  This includes
your printer, external drives, modems, and other peripherals. Modems, for
instance, have +/- 12 volts on its pins.  Damage can result when these
pins accidently touch the wrong pins on the computer.  Always check to see
that you have the appropriate cable and cable adaptions before you attempt
usage.
 
11) Don't guess where the cables connect.  Look where you plug your
equipment.  The A2000 has a round DIN connector for the keyboard. Always
make sure the connector marker is on top before plugging.  Don't do as
many people do.  Don't insert and then twist until it fits.  This will
slowly damage your connectors.  IBM PC keyboards are not compatible.
 
12) Be very careful that the metal band around your mouse connector
doesn't short the pins of the mouse port when inserting.
 
13) If you encounter a power failure, turn-off all your equipment. When
power is turned on by your Electric Company, your equipment may experience
damaging power spikes or fluctuations.
 
14) Remove disks when shutting-down a system. Park your harddrive if it
is not the auto-parking type.
 
15) Video monitors develop high levels of static electricity.  It is best
to plug the monitor and computer into the power outlets before connecting
the monitor cable. Always use a 3-prong power outlet. If your monitor plug
wasn't designed with a ground prong, use a power outlet that is correctly
polarized.
 
16) Always snug and not tighten the thumbscrews or clips to your
connectors.
 
17) Never place magnets near your monitor.  This includes speakers,
printers, and telephones which develop magnetic energy.
 
18) Be sure to include in your startup-sequence file a stack command.
However, programmers should check the stack size if they need more than
4000 bytes-Operating System overhead. I *don't* increase my stack, or if I
do it's to 8000. (Now you know what me, myself, and I do.)
 
19) Before working on the interior of your computer, always touch either
the disk drive's or power supply's metal casing to discharge any damaging
static electricity.
 
20) The Amiga monitors have a metal shield installed under the casing. If
you are using a non-Amiga monitor, make sure that your monitor has some
shielding or make one using a metal kitchen tray (?).
 
21) Don't mix and blend versions of operating systems. You are asking for
problems and will get them most of the time. If you are still using older
software, you are asking for problems anyway.
 
22) When paying for shareware and you want a response from them, cut the
bill in half and staple a note as to where the other half went. Nah, don't
do it; it's illegal.  Darn my buckies!  I just became a felon when I
thought
of an excellent programmer.
 
23) When plugging in cards for the A2000 Amiga, there is the end of the
card which screws to the back of the Amiga.  The metal bracket, which is
attached to the card for this purpose, has a tendency to catch at the
bottom of the bracket to the casing of the Amiga.  To seat properly, the
bracket must be pushed against the back of the Amiga and then it will move
further down.  Make sense?  The main point is: Don't force the bracket to
seat and especially don't use the screw to force it to seat! Always screw
the cards down to prevent shorts
 
24) Genlock for the Amiga may need some modifications to sync properly.
The modification needs to be done on the early models and requires that
R55 resistor be removed and R108 to be changed to 1.5K ohms. R55 is a
4.7K ohm resistor located near the Q3 transistor, and R108 is a 1K ohm
resistor located near pin#10 of the MC1377 chip.
 
25) The composite video of the Amiga A1000 needs color correction. Your
red, greens, and blues may not look correct.  The modification is simple;
just remove resistor R140; located on the rear-left of the motherboard. On
some A1000's, R140 will have to be replaced with a 470K ohm resistor
instead.
 
26) CORRECTED!
 
27) Keep your equipment out of sunlight; even when reflected by mirror or
walls while you are away from home. Overheating problems are increased if
the power supply vents are blocked or if it is resting on a rug. Keep the
power supply in a well ventilated area.
 
28) You cannot keep your cat or dog's fur out of your internal disk drive.
The fan sucks through there. Internal drives now have spring loaded doors
on the front which help in reducing contamination.
 
29) A clean mouse is a healthy mouse.  Clean your ball and rollers with Q-
Tips, rags, toothpicks, picks, and jack-hammers.
 
30) Sticky keyboard keys?  Remove that key button with a chip puller and
clean both button and switch with Q-Tips and alcohol.  If your lucky, the
shank of the key switch isn't split.  If it is, The split will widen in
the switch and wedge. Replace the switch or oil the shank with 3in1 oil
only. You may get lucky and find a repair station with some damaged
keyboards with good switches.
 
31) Does your monitor seem to sink into your A1000 computer case? Put a
plywood or 1/4 inch plexi-glass platform underneath. Does your A2000
keyboard seem to sink in the middle? Re-enforce the middle of the
keyboard's circuit board with a rubber spacer. Does this list seem a bit
long? Make some hot apple cider and come back here.
 
32) If one or more of your mouse buttons goes flaky, it can be replaced.
If the switch is "Flag", with a square body about 12mm in size with four
leads you may be in luck.  If the switch is the type where the actuator is
completely flush to the switch body, the replacement part can be had from
Panasonic; Digi-Key (1-800-DIGI-KEY) sells it as part #P9950, 36 cents
each. If the switch button is slightly raised from the main body (by about
1mm) you will either need to adapt the above part or try and find a better
match.  Mouser electronics (817-483-4422 or 619-49-2222) part # 10KB001,
49 cents each, *might* do the job. Some mice switches are dual switches
with only half being used! Use the other half by rotating the switch 180
degrees.
 
33) GET MEMWATCH from John Toebes!!
 
34) CORRECTED!
 
35) Dead Issue.
 
36) Ribbon cables should never be bent at angles to the degree of being
sharply folded.  All folds of ribbon cable should gently loop.  A sharp
crease can damage, short or break the wires inside the ribbon cable.  In
the cable from the disk drive mechanism, this can mean Guru's or the
device not being recognized.  MANY RIBBON CABLES FOR THE BRIDGECARD HAVE
BEEN DAMAGED BECAUSE OF THE CREASES IN THE PACKAGING OF THE PRODUCT. THIS
HAS DAMAGED DRIVES AND BRIDGECARDS. IF A RIBBON CABLE IS SHARPLY FOLDED,
USE AT YOUR OWN RISK.
 
37) Copy and run questionable or unknown programs in RAM disk with your
disks removed or write protected.  This will prevent you from crashing the
disk drives and damaging the disks.
 
38) Corrected!
 
39) For A2000 users with BridgeCards, keep the ribbon cable going to the
5 1/4 floppy away from the motherboard. Lay the ribbon cable on top of the
cards instead of underneath.  The ribbon cable picks up interference which
can cause your machine to intermittently GURU or cause devices not to be
recognized. (*** note *** Some A2286 bridgeboards will display parity
errors. Return these for exchange.)
 
40) All computer equipment need a minimum amount of time before powering
back on-line.  For the Amiga A1000 and A500, you must wait a minimum of 20
seconds before power-up and as long as 30 seconds or more for the A2000
Amiga. Computers need time to completely power-down and discharge all
voltages which may be sustaining corrupted data in RAM and other chips.
 
41) If your computer monitor remains powered and unattended for extended
periods of time, use a display blanking program.  This type of program
will "black-out" your display until there is some kind of user action from
the mouse or keyboard.  Your display will temporarily "black-out" after a
set number of minutes of inactivity.  Public domain programs like "PopCLI"
from the Software Distillery and "ScreenSaver" from Perry Kivolowitz are
good examples.  Leaving the colors stationary for days on end will
burn-out the phosphors of the monitor leaving you with a ghost image
of the display forever. I set my screen to black-out after 10 minutes of
inactivity.
 
42) It's a good idea to assign your T: directory to RAM:T before executing
any command script. The reason is increased speed and less drive activity.
 
 
(Hans Hansen)
Newsgroups: comp.sys.amiga
Subject: Screen colors and other boot things
Date: 16 Jul 87 01:42:24 GMT
 
Dark gray            Ok Hardware
Light gray           Ok Software
Red                  Bad ROM Checksum
Green                Bad RAM
Blue                 Bad Custom Chips
Yellow               Exception
 
(INITIALIZATION FROM OS ROMS)
Clear Chips
Disable DMA and Interrupts
Clear the Screen
Check the Hardware
Pass or fail the Hardware to the Screen  (BLUE|BAD) (DarkGray|OK)
Checksum the ROMs
Pass or fail the ROMs to the Screen    (RED|BAD) (LightGray|OK)
System setup (..is finished)
 
Check the RAM at $C00000
Move SYS_BASE to $C00000 if it exists
RAM Test ; hummm.... not very good though needs to indicate hex location
Pass or fail the RAM to the Screen (LED Blinks 9short 1long | GREEN | BAD)
Check the Software
Pass or fail the Software to the Screen  (Yellow|BAD) (LightGray|OK)
Set up the RAM
Link the Libraries
Find External RAM and link it to the list
Set up Interrupts and DMA (for boot drive especially)
Start default Task
Check for 68010, 68020, and 68881
Check for an Exception (System Alert?)
System Reset (..Let the good times roll!)
 
 
Hope this helps....
 
 
--
 -------------------  // ----------------------------------------------------
  Erick Parsons      //  Knowledge is little more than  knowing the questions
  -------------     //   [email protected] or ..ames!pacbell!sactoh0!americ!erk
  Sacramento Ca \\ //    GEnie: E.PARSONS      %-)       Hamatuer Radio N6RZB
 --------------  \X/ --------------------------------------------------------

Well, after getting more harddisk R/W errors than I like, I decided it's time to 
open her up and try adding the 1k pullup on the BAS line.  Being a hardware type
I thought it would be a good time to bring my machine upto rev, reformat my HD's
and perform other general maintence.  

I have an B2000 rev 4.2, 2090A, 2 ST225's, 2 internal Chinon floppies, standard
1M memory, 1084S, V1.2 ROMS and WB1.3.  I opened her up on the weekend and boy 
is dusty!  First priority was to recover as much from my HD's as possible.  My
last error left my HD1 "validating", yeech.  Deleting things on HD0 I seldom 
use and moving PD games, pictures and Demos to floppies I cleaned up enough 
room to put everything I wanted on HD1 onto HD0.  I upgraded WB1.3 to WB1.32 
then formatted DH1 (cyl 2-14 SFS), HD1 (cyl 15-614 FFS), copied everything from
HD0 to HD1 and repeated the process for DH0 and HD0 (same partitions).  Now it's
time to fixup the hardware...

Searching through the notes I came across this note which appears to have some
VERY useful revision information but lacks some details.  Can anybody shed any
more light on this OR know of any other things I should consider doing to make
my 2000 more ERROR and GURU free.

Here's what I am looking at:

>1084S-Philips (very similar to 1902A)
>   1) Nothing
>      a) bad R475 (15K 2w flame) damaged from bad C476 (.047uF, 250V)
>      and T402. Between June 88 and Sept 88 require warranty repair.
>      1084S-P monitor repair kit PN# 314891-01 billed $44 and credited
>      when T402 is returned to parts depot with NARDA form.
 
This one looks ok.  My manufacture date is November 88.

>A2000 (see also A500 & A1000 & A2500 for hints)
>
>   5) First character from keyboard missing after power-up
>      a) cut out C910 & C911; CBM modification.

Really?  Are these on the motherboard or in the keyboard?

>  12) Modifications:
>      a) Replace U602 and U605 (74LS245) with 74ALS245
>         Make sure that 74XX24(4|5)'s between Agnus & Ram are F types
>         the symptoms include spots appearing on screen
 
U602 and U605 look ok. My are TI 74ALS245's.  Still need to find the others
between Agnus & Ram.  What's F type?

>      b) Cut-out C910 and C911
 
Same as 5) above.

>     c) Put noise by-pass cap (.01ufd) on ElTek power supply TICK line
>      across R65. All the Eltek power supplies needed to be checked that
>      a .01 MFD capacitor was installed across R65 to suppress noise and a 
>      "00" with a line through it written on the power supply label.

I have an ElTek power supply with no apparent "OO" with a line through it so
I guess I need to look at this.  R65 in the power supply?

>      d) Check for proper usage of ferrite beads at video connector

Any idea what "proper usage" is?

>      e) put 3300 ohm resistor between #20 & #11 of U605

This is the change I hope will help my frequent R/W errors as I remember seeing
someone else mention that it helped even with just a 2090x configuration.  I saw
the other note from CBM indicating they used a 1K on their boards for the pullup
so thats what I plan to put in.  

>      f) Read TechTopics Issue #25 Section #3 (Apr-May-Jun 89) for details
>         1) remove R901, C917, C902, C910, C911, C905, C908, C230, C240
>         2) replace 1.2 KickRom with 1.3 or latest version
>         3) if U205 & U206 are 74HC244 install RP904, RP905, RP906
>         (4.7Kx5); if they are not DON'T install (e.g. 74HCT244)
>         4) add .01 UFD cap on J300 center connector to ground pad
>         5) add 470 ohm resistor to D800 cathode to second pad from the
>         left, under CN605. 4.3 rev boards and up have R1000 left of Q302
>         instead.
>         6) if R5719 installed, add 470 ohm resistor between VCC and CPU
>         side of R106.
>         7) Replace ALL Gary chips (5719) with MOS type p.n. 318072-01
>         8) Install new reset chip MITSUMI PST518B into ALL rev 6 boards
>         (see TechTopics 25/3-3.1)

This sounds VERY interesting.  Anyone know what "TechTopics" is and how I can 
get a copy?

Other fixes?  Well I plan to upgrade to 1M Chip RAM after I can afford to add
another 2M Fast RAM.  I going to skip 1.3 ROMS and wait for 1.4 and enhanced
chip set.  I can live with no autoboot for now.  I also remember reading the 
2090x has problems that to 2091 solves.  Any idea if the 2090x will ever be
ECO/FCO'd?

Thanx for any help

...Ed

    Hi Ed, how's it goin'.
    
    I can help you with one of these...
    
>>A2000 (see also A500 & A1000 & A2500 for hints)
>>
>>   5) First character from keyboard missing after power-up
>>      a) cut out C910 & C911; CBM modification.
>
>Really?  Are these on the motherboard or in the keyboard?
    
    Since the day I got my B2000 ( Rev 4.3 ) the keyboard would hang up from
    time to time. A power reset of the keyboard or the whole system would
    sometimes clear it. About the same time as I first saw this it was
    constantly hanging and I was about to take it in (something not easy
    for us hardware types ;^)  ). 
    
    I think the schematic shows caps C901 and C911 (on KBCLK and KBDATA) as
    being on the mother board but there are also caps on the KBCLK and
    KBDATA lines inside the keyboard. I clipped the two inside the keyboard
    and have never had a keyboard hang since.
    
    It seems to me that  either the mother board or the keyboard should
    have the caps (noise filtering??). Maybe the keyboard poeple and the
    motherboard poeple got their wires crossed.
    
    	Regards...   Clint
    
    P.S. I have the A2090a and a ST225, no problems at all so far.

    Concerning this topic -- I was in the same process of deciding what
    mods to make since I'm opening my system up within the next 10 days.
    You seem to have reached the same conclusions I have, and
    your posting asked the same questions - so I'm looking
    forward to the replies posted here.
    
    Concering The keyboard caps. My feeling was that since I don't seem
    to be having any problems in this area - I'll skip this mod. I assume
    that the problem is that your first character(s) typed don't appear,
    or that the keyboard is hung but the mouse works - neither problem
    have I seen on my system.
    
    

Well I put Amy back together last nite and got everything running again.
I thought I'd provide an update for any others that care to venture inside...

There were only a few changes I made and in the process I discovered that
my A2000 manual actually has A1000 prints (labeled 2000 of course) in it.
Was this corrected in the newer manuals?  This made it impossible for me
to make some judgement calls on the suggested changes as I couldn't determine
what I would be effecting.  I must get a new printset...  I also discovered
that when I added my second ST225 I neglected to remove the terminator from
the first drive!!!  Likely the reason for my disk problems.

Anyway here's what I checked/did

- 1084S no problems
- U602 and U605 were ok (74ALS245's)
- 74XX24(4|5)'s between Agnus & Ram were ok (F types)
- C910, C911 were still installed and I opted to leave them for now as I have
  not had any keyboard problems.  Also my keyboard is a older one (small
  FUNCTION keys) and I not sure this change applies.
- 0.01 uf capactor across R65 in the ElTek supply.  I checked and it appears 
  I don't have this mod.  I was temped to install one but feel I am lacking
  enough details.  I may go back in and do this one after I'm sure AMY is ok
  from the other changes I made.
- ferrite beads at video connector, well I got some but not sure what is the
  "proper useage" mentioned.
- 3300 ohm resistor between #20 & #11 of U605, well I added a 1K 1/4W 5%
  resistor here instead of a 3300 ohm.  This is what CBM is using I here.
- R901, C917, C902, C905 C230, C240 were already removed
- C908 is still installed and decided not to remove until I see a proper
  printset
- U205 and U206 were 74HCT244's hence no resistors packs required.
- 0.01 uf cap from J300 center connector to ground not present or added until
  I see some prints.
- 470 ohm from D800 cathode to gnd not present or added until  I see some 
  prints.
- 470 ohm from VCC to R106 not present or added until  I see some prints.
- GARY chip not MOS type.  I guess I'll look for one of these at the next flea

One other strange thing I found is that 1 row of my memory chips had their
bypass capacitors removed (C525-C532).  Has anyone else noticed this?  I may 
try and phone  the author "Bruce" and get a copy of the TeckTopics he mentions.


...Ed

    Considering that I have a (believe it or not) a REV 4 board - I'm very
    interested in your findings and the response you get concerning the Tech
    Topics. Too bad you didn't add the power supply cap, as that is one I
    have decided to do. (what REV level is your board anyway?)
    
    I'd also be interested in the MOS chips, as I'm sure I'll need that mod.
    I'm adding a Fatter AGNUS this weekend and will check things out.
    
    					{kgb}

While you are in yours please check if you have a row of memory caps removed.
I interested why this was done and if it really should have been.


...Ed

	Well, I finally got to upgrade my system. I originally thought I
had a Rev 4.0 motherboard, but after I took everything apart I found a sticker
that stated it was a Rev 4.1. I took a trip to my dealer to pick up my Fatter
Agnus, and to examine his Tech Book concerning installation and any ECO's to
the Amiga 2000 (with the intention of comparing this information with the
USENET "Flake Report" mentioned several times in this topic). Here's what I
found:

	With the exception of 1 or 2 items in the USENET list; almost
everything listed as an AMIGA 2000 ECO is part of the CBM Tech Report for
upgrading an Amiga 2000 Rev 4.x to a Rev 4.5 (entire list will be presented
here). My goal was to install the Fatter Agnus and perform the Rev 4.5 upgrade
as best I can, and perhaps include the extra stuff listed in the USENET posting.

There weren't that many newsletters - most were updated releases of previous
letters stating the same procedures. I examined everything and grabbed what
I felt was the most useful and current. There were no letters on bridgeboards
or Genlocks; there were some on the Rev 4.5 upgrade, Rev 6 fixes, A2620, and
power supplies.

				--------

Here is the entire Rev 4.5 upgrade; as described in the CBM Service Technican
Report; Issue #26 - JUL-AUG-SEP 89. The CBM Tech Reports were the reports that
USENET referred to as "Tech Topics".


THE FOLLOWING INSTRUCTIONS DETAIL THE CHANGES WHICH MUST BE IMPLEMENTED TO
UPGRADE A U.S. A2000 PCB FROM REV 4.0 (or higher) TO REV 4.5.  CURRENT
PRODUCTION BOARDS ARE EITHER REV 4.5 W/O NEW AGNUS, OR REV 6 W/ NEW AGNUS. ALSO
NOTE: SOME REV 6 PCBS MAY HAVE A DRAM TOWER AND STATIC COLUMN DRAMS, SOME MAY
NOT. FIELD UPGRADES ARE NOT RECOMMENDED ON REV 3.X PCBS.


26/3-2.1	A2000 FIELD UPGRADE TO REV 4.5

	1) THE FOLLOWING COMPONENTS MUST BE REMOVED IF INSTALLED.

		R901, C917, C902	LOCATED LEFT OF CN601 NEAR PIN 1.

		C910, C911		(FIX FOR HYTEK KEYBOARDS). LOCATED
					OFF KEYBOARD CONNECTOR, CN300)

		C905, C908		C908 LOCATED ABOVE CRYSTAL X1
					C905 BELOW GARY PIN 20

		C230, C240		LOCATED ABOVE U204, U303 (BETWEEN PIN
					34 OF THE DRIVE CONNECTOR AND U301)

	[Ed note: my system had all of these removed already]


	2) REPLACE 1.2 KICKSTART PROM WITH 1.3

	[I did this a long time ago]


	3) INSTALL RP904, RP905, RP906 ONLY IF U205 AND U206 ARE 74HC244 TYPE
	   ICS (RESISTOR PACK IS 4.7K OHM X 5, 6 PINS). DO NOT INSTALL IF ICS
	   ARE 74HCT244 TYPES. RP905 IS LOCATED BETWEEN U205 AND U206. RP906
	   IS LOCATED BETWEEN PAULA AND DENISE. RP904 IS TO THE RIGHT OF
	   DENISE.

	   [My ICs were HCT type so this change was not required]


	4) ADD .01uF CERAMIC CAP ON J300. ADD THIS CAP ON SOLDER SIDE OF PCB,
	   FROM PIN 12 (MIDDLE PIN ON CONNECTOR) TO GROUND (USE EITHER GROUND
	   PAD LOCATED ON SOLDER SIDE, DOWN AND TO THE RIGHT - ABOVE PAULA
	   PINS 46 AND 48).

	   [J300 is the jumper that selects which clock (video or line
	   AC) signal is used to drive the RTC. My system was one of those
	   that was originally shipped with the jumper incorrectly set to
	   "video", and I had to change it and re-adjust the clock speed; so
	   I decided to install this ECO on the basis that it involved an
	   area I had previous problems in. I installed the cap and later,
	   when I rebooted the system, double checked the clock against
	   CBM's SYSTEST - I didn't see any difference or notice any during
	   use. I don't know exactly what this was suppose to cure.]


	5) ADD 3.3 OHM 1/4 WATT RESISTOR TO PINS 11 & 20 OF U605.

	   [Some have used a 1k resistor here instead. U605 is also
	   one of the 2 ICs that the USENET posting said should be changed
	   from 74LS245 to the faster 74ALS245 if applicable. My chips were
	   the slower ones, so even though others have done this ECO without
	   problems; I wasn't sure if I should if I should eventually replace
	   the chip too. Plus I wasn't comfortable with my ability to do this
	   safely. In a different CBM ECO, I found a writeup on what this was
	   suppose to cure:

		A2000 74ALS245 BUS TRANSCEIVER RESISTOR

		AMIGA 2000 SYSTEMS USING SOME EXPANSION HARDWARE, SUCH AS
		A2090A, IN CONJUNCTION WITH A COPROCESSOR CARD (A2620)
		REQUIRE A 3.3K OHM RESISTOR TO BE SOLDERED FROM PIN 11 TO
		PIN 20 ON THE 74ALS245 (ed: note the chip number) BUS TRANS-
		CHIP AT U605. THIS RESISTOR IS TO BE CONSIDERED PART OF THE
		STANDARD INSTALLATION PROCEDURE FOR A A2620 CARD.

	  I'm not having any expansion hardware problems and don't intend
	  to get an A2620 - so I skipped this change entirely]


	6) ADD 470 OHM 1/4 WATT RESISTOR TO D800, CATHODE SIDE, TO THE
	   SECOND PAD FROM THE LEFT, UNDER CN605. (D800 IS LOCATED TO THE
	   LEFT OF THE RTC AT U801). NOTE: ON REV 4.3 AND ABOVE THIS
	   RESISTOR IS ON PCB AS R1000, LOCATED TO THE LEFT OF Q302.

	   [Didn't know what this was for and I didn't have a 470
	   OHM resistor handy (this wasn't listed in the USENET posting) -
	   so I skipped this]


	7) IF R5719 IS NOT PRESENT (LOCATED OFF PIN 1 OF CN400) ADD 470 OHM
	   RESISTOR BETWEEN VCC AND CPU SIDE OF R106.

	   [This didn't apply to my system - R5719 was present]


	8) REPLACE GARY IC AT U102 WITH MOS TYPE (PART NUMBER 318072-01).
	   ONLY MOS TYPE ARE IN STOCK.

	   [This applied to me, but I didn't have the chips. I had heard
	   a rumor that the ECS may have a new GARY in it, so I'm going to
	   hold off on this until after the ECS comes out].


			End of 4.5 upgrade


In addition to this list, I also added my Fatter Agnus chip (which required
a jumper move and cutting a solder-pad connection also). Since several
people have installed this I will skip these instructions.


The only other item of interest to me was only in the USENET posting (so I
assume it is not a CBM change):

	1) ADD A .01uFD CAPACITOR ACROSS R65 ON ElTek POWER SUPPLY TICK LINE
	   TO REDUCE NOISE.

	   [I wanted to install this but was unable to determine if I
	   had an ElTek power supply and I couldn't locate R65 - so I had
	   to skip this].


				------

I rebooted my systems and ran it through SYSTEST - passed with flying colors.
Booted my workbench and used it for a while - all seems healthy!!! :-) :-)


				------

These Service letters did not apply to my system, as they refer to Rev 6
PCBs. I'm including them for others that may be interested.


	26/3-4.1	A2000 CR REV 6.0 PCB EXPANSION BUS PROBLEMS

	IF PROBLEMS ON A2000 CR REV 6.0 PCB'S OCCUR, SUCH AS GURU CODES,
	AUTO-CONFIG OR SYSTEM HANGING UP, WITH SOME 3RD PARTY ADD-ON
	CARDS IT MAY NE THE RESULT OF THE MOTOROLA TYPE 68000 CPU ICS WHICH
	HAVE A MASK CODE OF 0B26.

	PARTS IS STOCKING SIGNETICS TYPE 68000 UNDER PART NUMBER
	390084-03


	26/3-3.1	A2620 COPROCESSOR ROM UPGRADE

	NEW ROMS ARE AVAILABLE TO UPGRADE THE A2620 FOR USE WITH SOME 3RD
	PARTY HARDWARE ADD-ON BOARDS (GVP TYPE). THIS IS A RUNNING CHANGE
	AND IS NOT COVERED UNDER WARRANTY. BOTH U4 AND U5 MUST BE CHANGED.


	25/3-3.1	A2000 GURU MESSAGE ON POWER UP W/ REV 6 PCB

	NEW DRAMS MAY RETAIN DATA FOR AS LONG AS 5 MINUTES AFTER POWER OFF.
	AN ADVISORY MESSAGE ON POWER UP MAY INDICATE THAT THE ERROR
	GENERATED BY POWER OFF HAS BEEN RETAINED, AND PRESSING LEFT MOUSE
	BUTTON WILL ALLOW STARTUP TO RESUME.

	A MITSUMI PST518B RESET IC SHOULD BE INSTALLED [diagram and
	instructions followed]
    

Looks like I'll open Amy again and finish upgrading to the latest rev...

A few observations/questions:


>I installed the cap and later when I rebooted the system, double checked the 
>clock against CBM's SYSTEST -

What's CBM's SYSTEST?  Are you refering the the powerup diags?


>4) ADD .01uF CERAMIC CAP ON J300. ADD THIS CAP ON SOLDER SIDE OF PCB,
>	   FROM PIN 12 (MIDDLE PIN ON CONNECTOR) TO GROUND (USE EITHER GROUND
>	   PAD LOCATED ON SOLDER SIDE, DOWN AND TO THE RIGHT - ABOVE PAULA
>	   PINS 46 AND 48).

Could this the same fix as putting the cap on R65 in the ElTek power supply?
That fix was to reduce noise on the TICK line causing clock problems.  Are we 
talking about the same clock here?


>5) ADD 3.3 OHM 1/4 WATT RESISTOR TO PINS 11 & 20 OF U605.

Interesting that this report indicates a 3.3K while in another NOTE there is
a mail from CBM (Dave H?) indicating they are using a 1K.  Does anyone with
a Rev 6.x board know what value they have?


>7) IF R5719 IS NOT PRESENT (LOCATED OFF PIN 1 OF CN400) ADD 470 OHM
>	   RESISTOR BETWEEN VCC AND CPU SIDE OF R106.
>
>	   [This didn't apply to my system - R5719 was present]

Was R5719 labeled?  I have a rev 4.2 and couldn't find this resistor.


>1) ADD A .01uFD CAPACITOR ACROSS R65 ON ElTek POWER SUPPLY TICK LINE
>	   TO REDUCE NOISE.
>
>	   [I wanted to install this but was unable to determine if I
>	   had an ElTek power supply and I couldn't locate R65 - so I had
>	   to skip this].

My power supply had a label on the side with ElTek's name on it.  I had to 
disassemble the supply to locate R65 but it was there with no visible capactor
across it.  Looking at the main power supply board R65 is located on the back
edge middle left.  It was labeled.  I was hesitant because there was also a 
green ECO wire in the same area and I was unable to determine (without a great
deal of effort) it's function.  My fear was that the Cap may already be 
installed at the other end of the wire.  Now I have had everything running
for a while I may try and add this one anyway.


Regards,

...Ed

    Concerning SYSTEST:
    
    SYSTEST is a program that (at least in the beginning days) CBM used as
    a final systems check. I got it about 2 years ago from my dealer. It
    tests sound, graphics, disk, chip, fast ram, and RTC accuracy. I'll
    upload it to TAPE::
    
    
    Re: 4) .01uF capacitor
    
    I don't think it's the same thing - this jumper affects the RTC I
    believe. Can someone verify this? If it is, then I installed the ECO
    I was interested in :-)
    
    
    Re: 5) resistor rating (1k?)
    
    I'd also like to know this also.
    
    
    
    Re: 7) R5719
    
    I honestly don't remember now. Taking apart your $n000 computer is very
    nerve wracking! I think I just looked and saw what I believe to be it.
    It's very possible I simply screwed up and skipped this ECO anyway.
    
    
    Re: ElTek power supply
    
    Hummm. I had no such sticker. Is this resistor on the motherboard or
    the power supply board? Non of the components on the power supply board
    were labeled and I had no diagrams.  Can you describe the location of
    this resistor?
    
    
    
    Other items:
    
    I called and found out the price of a MOS GARY is about $18 - so I
    ordered one anyway. I don't plan to take apart my system again for a
    long while however, so it may sit on a shelf for a while.
    
    
    A friend who has a "fully stocked" system (harddisk, memory,
    bridgeboard, etc) with little or no backplane slots left pointed out
    that his system doesn't even get close to getting warm inside. His
    opinion is that the Amiga fan is very (over?) powerful. An idea came up
    that perhaps adding a resistor to the fan would slow it down, reduce
    the noise, without any risk to the system. What do you think?
    

>    SYSTEST is a program that (at least in the beginning days) CBM used as
>    a final systems check. I got it about 2 years ago from my dealer. It
>    tests sound, graphics, disk, chip, fast ram, and RTC accuracy. I'll
>    upload it to TAPE::

Yes please do!

>  Re: ElTek power supply
>    
>    Hummm. I had no such sticker. Is this resistor on the motherboard or
>    the power supply board? Non of the components on the power supply board
>    were labeled and I had no diagrams.  Can you describe the location of
>    this resistor?

It doesn't sound like you have an ElTek power supply.  R65 is on the power 
supply board and all the components on mine were labeled.  When I open Amy up
again I make a note of it's exact location.


>    A friend who has a "fully stocked" system (harddisk, memory,
>    bridgeboard, etc) with little or no backplane slots left pointed out
>    that his system doesn't even get close to getting warm inside. His
>    opinion is that the Amiga fan is very (over?) powerful. An idea came up
>    that perhaps adding a resistor to the fan would slow it down, reduce
>    the noise, without any risk to the system. What do you think?

That might work but if it does get too hot it's a high price to pay for some
silence.  When I first got my 2000 I was very bothered by the fan noise and
followed other's suggestions to replace it with a Radio Shack one.  Well I did
that and tested the fan before installing it and it was very quiet.  Then I 
installed and the noise level was the same as with the old fan.  I conclude
the problem is an isolation problem and not a noisy fan.  Perhaps rubber 
mounting the power supply would help?  There isn't enough room to rubber
mount the fan itself.  I have also considered lining the inside of the case
with high density foam and sitting the 2000 on a piece of the same.

...Ed

    
    Does any of the info in this note + replies apply to the A500?
    
    I would like to see the same kind of discussion for the A500,
    if anyone could "tell all".  I found the USENET posting a 
    little confusing.
    
    Thankx,
    A puzzled A500 owner,
    Dennis
    

    The items posted here only aply to the 2000. I did not check out the
    500, nor do I have anything. I suggest that someone ask a repair
    center if CBM released any Technical Notices for the 500.