price@MANDALA.UNL.EDU (Chad Price) (08/23/90)
Some weeks ago I posted a query in this group about parallel port
problems I was having which seemed to be the fault of my HP IIP.
After buying the IIP, I had had 3 parallel ports quit working: a builtin
port on a PS/2 Mod 50, an original port in a Zenith 386-16, and an
Everex replacement in the Zenith.
I got no responses indicating that other people were having the same
problems; but I did get interested queries from HP engineers (both
technical support and design, including the engineer who designed the
parallel interface for the IIP).
To make a long story short, the HP engineers eventually pointed me in
the right direction. The source of the problem was the wiring circuits
in the building. All of them appeared to be 3-wire outlets. Since the
entire room where the printer and computers reside is (was) on the same
circuit, I had plugged the laser printer into another outlet in another
room via a heavy-duty extension cord. The 3-wire outlets in the one room
were NOT 3-wire, they were 2-wire, with the polarity of the current
REVERSED. The printer was plugged into a correctly wired outlet.
Apparently the reverse polarity in the computers, and the correct
polarity in the printer set up some sort of load (I'm not an EE-type at
all) on the chips in the parallel port and eventually fried them.
The solution: 1) correct the polarity, 2) wire the ground to neutral at
the outlet, 3) Install separate circuits for the printer and the
computers.
The Diagnosis:
1) check the outlets with a multi-meter - the non-grounded
outlets will show some current between neutral and ground (mine
showed 45 volts) and there should be none. THe ground to hot
connection should show 115 volts and mine showed 75 volts.
2) Pull the outlets out of the wall and look at the wiring. In
the US, hot should be black, and neutral should be white. Ground
is usually a bare wire. Hot should be the smaller plug socket
where they are different sizes.
neutral hot
| |
_ ground
Note: when I rewired, I had the entire circuit disconnected at the
breaker-box. I had a professional electrician come in and install the
new circuits.
In closing, I would like to publicly than all those HP personnel who got
involved in my problem through the net. Your help was invaluable and is
one of the primary reasons I continue to be willing to buy HP products
at somewhat higher prices than other brands: HP Provides support and
excellent QUALITY.
Chad Price
price@fergvax.unl.edu