CIA Woes!
30 messages in this thread
Here is where I would really welcome some input..
I have been through 4 CIA chips in the past 6 months. I consider myself
to be generally cautious with my equipment, but I must be doing something
wrong here.
My parallel port is connected to an A/B switchbox (metal case, plastic
rotary switch/knob). I think that I may have been causing damage by using
the switch, esp. while the peripherals I'm switching between are ON. I was
most often switching between A) a PAR-NET cable and B) my printer.
Sometimes I would use Digi-View or Perfect Sound in B) instead (only
plugging/unplugging from 'B' when the unit was switched to 'A').
Current Status: System freezes when printer runs out of paper (paper-out
signal), computer keeps incorrect time (the volatile system clock), and
Digi_view, P.Sound and PAR-NET are un-usable.
Now, I only turn the switch when all peripherals are OFF to try to
prevent further damage. However, I do not want to invest in replacement
chips until I am sure of the culprit.
Christopher,
Your problem is obviously related to attempting to expand your A500
beyond that for which it was designed! (<grin>)
On a less sarcastic, more serious note: I have been told that many
switch boxes are designed with a parallel printer in mind, in which case
they are only expecting one-way communications, and are designed
accordingly. I seem to remember such a warning either in the Perfect Sound
manual or in one of the "read.me" files included with the Perfect Sound
package. Since the devices to which you are switching are talking 2-ways
on the Parallel Port, this may be part of the problem. I know that I have
decided to do the power-down/reconnect peripherals when switching to/from
my Perfect Sound, rather than attempt to use one of the many switch-boxes I
have sitting around here because of this warning.
Good luck in tracking this down, and hope this helps….
…BobR
Thanks Bob (for the serious stuff, anyway 🙂
I opened the box and looked around. All there is to it is this
Frankenstein-looking rotary switch, having dozens of wires coming out it's
side and to the DB connectors. It looks very well-made. As for two-way
data, there seem to be no electronic components such as diodes,
transistors, capacitors, etc. that would hinder two-way communication.
Here's the scoop on the pass-thru: All pins passed thru EXCEPT 17-25,
which are all soldered together and use a single wire. According to the
parallel port schematic, this should do just fine (I have NEVER used this
for Serial). I remember when I first got the switchbox that I did a
continuity test on all pins, for both 'A' and 'B'. All the connections
seemed good and (except 17-25) were completely isolated (no shorts or
crossovers).
Make sure it's a 'break before make' type switch (which is probably
what it is). Versus a 'make before break' switch.
The difference between them is that break before make type switch
disconnects from the 'A' side before it connects with the 'B' side (or vice
versa) whereas a make before break connects the 'B' side before it
disconnects from the 'A' side. in other words…all 3 connectors are
momentairly connected.
One other thing…those grounds (17-25) are probably connected all
the time between all three connectors…that's ok.
I wish I could look inside the barrel of the switch to see if it breaks
contact with 'A' before engaging 'B'; However, the barrel is rather
well-made plastic and steel, but doesn't look like the 'servicable' type of
component.
Easy way to test…simply put a continuity tester between a pin on
the A input and the same numbered pin on the B input (but not one of the
grounds though) and slowly flip the switch. If the tester jumps..or
indicates continuity at any time…you've got a make before break type
switch.
I tested the switchbox like you described with my Ohm meter set to
audible continuity-check. I tried several times, turning the switch as
slowly as I could back and forth.. Not a peep or a flicker in the display.
So I guess the switch is not the culprit.
Thanks for your suggestion; It eliminated a major unknown.
Question: Does/did your printer have a 3 prong cord, which has been changed
to a 2 prong; or, is it a three prong into a two prong (like into an
extension cord), such that the prongs could be turned around in the wall?
This can (and often has) blow out your CIA chips. Static… you need to be
*sure* that you touch the case of the amiga with the printer cable shell
*before* you plug it in. This dicharges and delta-EMF between the printer
and the computer that was generated as a static charge (no matter how it
got there). Use the shell – NOT the area of the cables with the pins. Hope
this helps.
Ben
Amateur Radio Callsign is A A 7 A S
Ben,
As a matter of fact, I had the printer on a three/two-prong adapter for
quite a while; Not for lack of a grounded outlet, but because NewTek (and
others) recommend that only the computer should be grounded (the
peripherals using the computer's ground) to avoid a "ground loop"
phenomenon. I remember always pluging the printer in with the correct
polarity, but that is memory and I suppose just one time backwards is
enough to cause all this.
More about the PAR-NET cable.. It's 35' ribbon cable, unshielded,
running along the rug from the living room (which has the 'server') to the
bedroom (with the little 'client' setup). This runs from the client's
parallel port to the 'A' connector on the server's A/B switchbox. There is
also the 3' full pass-thru ribbon (unshielded) cable connecting the
server's parallel port to the switchbox.
Everything seems to work with the switchbox – Digi-View, P.Sound, the
printer and the net cable… For a while that is.
Ah… not to use too strong words here, but, whoever told you that "only
the computer should be grounded" is (1) out of their tree; (2) advising you
to do things that, if a fire were to start, are solid grounds for a
winnable, reasonable lawsuit; (3) have such little connection with reality
one has to wonder if the individual you spoke to has looked at anything to
do with grounds since the last time they burned their coffee.
Connect *all* your grounds. It's very likely that you will cease to lose
CIA's and so on.
Ben
Amateur Radio Callsign is A A 7 A S
Ben,
Is there any, uh, convenient way to ground my mouse, then???……. 🙂
— steve
It is grounded… the shell on the mouse connector at the AMiga end has (at
least all of them that I have seen) a metal shell that is connected to the
ground system. :^)
Interesting! This suddenly makes me realize that maybe some third-party
mice and/or joysticks do _not_ have that metal shell, is this risky? Or is
the ground across the pins adequate enough?
I would say that without that metal shell, you may or may not have a good
solid ground to the mouse. For RFI (FCC) reasons, a mouse cord is likely to
require a shield; and that shield should be connected to the shell of the
socket. That's usually what that metal shell on the cable connector is for
– a solid RF ground. Static being pretty well unpredictable, my position is
"the more ground, the better".
Hmmm, this is something to watch out for should one ever purchase
third-party mice and stuff. I've noticed most joystick connectors don't
have such a ground, is this something to start worrying about?
From my point of view, which is admittedly sort of a right-wing hardware
worst-case kind of view, yes. I look at the connectors before I buy
anything..
I have an extra worry, though – I'm a HAM radio operator, and if "things"
start emitting massive amounts of radio frequency energy, my radio
listening begins to suffer serious Bad Stuff.
I've also been victim of two dead Amiga's, so far, as a direct result of
static. One was killed by a SuperBase Dongle (plugging it in blew the
computer to hell and gone… static went right in the mouse port and
zing…) The other was an a1000 I plugged a SCSI controller into after
walking across the room. I saw the spark… it took a week of screwing
around before the machine booted again (from floppy!)
THis all tends to trend ones thinking towards the conservative side.
<painful laugh> thanks for the report on your experiences, I think I'll be
very careful around my ports from now on (as if I'm not already!).
I quote from NewTek's DigiView 3.0 *User's Manual*…
Q."I see…interference pattern in my digitized images. What causes this?"
A."This case of this is usually a ground-loop. A ground-loop can occur
when more than one of the components in your computer system are plugged
into your house current with a grounded (three-prong) plug. The computer is
the only component that should be grounded, all other components should be
un-grounded by using a 3 to 2 prong adaptor on their power cords."
Immediately following this paragraph, there is a section on diagnosing and
servicing damaged CIA chips!
If this really IS the cause of the damage, then can I hold NewTek
responsible? This is getting rather expensive for me.
You bet. Or if your house catches fire, or if you get a debilitating shock
from a reversed two prong cord, or an unisolated or reversed hot-chassis
monitor happens to kill your youngest child or your dog or your cat (nah,
cats are too smart) or your elderly grandmother.
AC current, as supplied in the wall of your home, is generally not
polarized – IE, one lead isn't any much more dangerous than the other. Both
(either) can KILL you. Some monitors (old ones, as far as I know) and
televisions, use what is called a HOT chassis. THis is where they take one
side of the AC line and connect it to the metalwork, which (here is the
kicker) is also usually connected to the signal ground, like the cable
wires and video inputs and so on. You notice that most AC plugs have one
prong wider than the other last few years? THat's so you can't plug in the
cord the wrong way. If you *do*, you have connected the opposite side of
the AC line to the montior/equip/.etc.
Now, in the three prong thingees, the ground (the third round pin) is sorta
the same as the side that is supposed to be common (ie to ground in HOT
chassis designs). You reverse the hot on your monitor, connect cable to
something else (like your Amiga) and you essentially have connected one
side of the AC line to the other, THRU your Amiga.
BOOM! THings die – maybe YOU, if you happen to be holding the wrong thing.
But probably your Amiga. You might be safe, those wider bladed plugs can
help.
Bottom line: One of the main reasons that we have those polarized plugs and
plugs with grounds is to make things safe. You defeat it, and you are
literally playing with fire. Don't do it. Ever. For any reason. Find
another solution.
And of course nobody ever mentions that the whole idea of 2 prong outlets
was the big con pulled by the electric companies around the turn of the
century to sell people on AC power rather than DC power! It seems like now
that everyone's forgotten that fact that they're now saying "you should
only plug things in one way" which is exactly what they told people you
wouldn't have to do anymore with AC power.
That's absurd. There's a major reason why sockets are polarized
now (and have been for perhaps 30 years or so)….your safety.
That's exactly my point. Back in the days (around the turn of the
century) when the power companies were supplying DC power, they switched
over to AC because it's much cheaper for them (and really everyone) for
several reasons. In order to convince people that they should switch over
to AC power (and replace any appliances that wouldn't work with AC) they
made a big deal that you wouln't need polarized outlets with AC (like you
do with DC).
Oh, Mike! That's the least of the differences between AC and DC power. For
my money, Tesla's system beats Edison's, no contest!
First… you should NOT have to worry about which way things plug in. The
reason that you DO, is because certain manufacturers took some rather
stupid liberties with the AC system, I'm speaking specifically of the
hot-chassis designs.
Second, N. Tesla, who espoused AC power over DC power, did so because he
felt (correctly) that AC power was a mcuh more efficient means of getting
energy from here to there; compensation for transmission losses was easy
and inexpensive (IE, transformers). DC power, as pushed on the public by
T.A. Edison, was not economically practical for this reason alone, although
there are others.
If there ever was a "Big Con", it was perpratrated on the public by Thomas
Edison, a man who has gone down in the history books as a positive
figure… when he (a) ruined Tesla with lies, propaganda, and just plain
idiot claims, and (b) foisted DC power off as a practical,
mass-distribution power system, which it was not then and is still not now.
Ben
Amateur Radio Callsign is A A 7 A S
Ben,
Completely agree (as usual <g>) about Tesla vs. Edison. But Edison was a
better businessman.
Malcolm
UNfortunately, then, as now, being a b*stard is usually an asset in
business. A lying, deceitful, self-centered b*stard, in T. Edisons case.
Ben
Amateur Radio Callsign is A A 7 A S
If you see me complaining to NewTek in AmigaVend, you'll know I could use
your input.
I'll give you input in here… you need opinion, ask. I'd rather not turn
on the NewTek section in Vendor… I'm about at my limit of message
reading/replying as it is.
Ah…and there is your problem more than likely. The 35 foot
ribbon cable running on the rug.
As I'm sure you're aware…significant static charges can build up
on a rug especially in the winter when the air is drier. The insulation on
a ribbon cable is not enough to stop that charge from getting in the wire.
Do one of two things. The best would be to use a shielded round
cable instead of a ribbon cable. That way…the static charge will go into
the shield and to ground with no effect on the operation. The other would
be to spray the rug where the ribbon cable is running with something like
Static Guard once a month. Spray it until the rug is damp…but not wet of
course.
(Oh…#1 above presumes the shield is connected to ground)
Thanks.. I can try the static-guard aproach, but the connectors on each end
of the cable are all-plastic (unshielded). I would have to rebuild the
cable to implement shielding, and then I'd have to find another use for 35'
of 14-wire ribbon cable.