18 May
2010
18 May
'10
12:31 p.m.
It may be just simpler to add an isolation transformer
to the monitor=2C or=
if its a 'hot' chasis just be sure the supplies of both systems have no di=
I wold not recomend that. As you know, I have nasty things to say about
health-n-safety, but I will not have any exposed metalwork directly
connected to either side of the mains supply. Period.
fference in hot and neutral. This was the original
IBM PC solution=2C reme=
mber the special polarized plug for the monitor=2C that plugged into the CP=
U?
No. The IBM MDA monitor had a mains isolating transoformer built-in. Im
fact the mains was stepped down to 12V to run the monitor electronics.
The CGA nonitor (which plugged into the wall, not into the PC's PSU) had
an isolating SMPSU.
The power output socket on an IBM PC PSU is just switched mains. It is
not isolated in any way.
I can think of 2 hot chasiss monitors used with computer-related
equipment. Both were converted TVs. One was a Philips used witha Philips
Viewdata set. The montor was a modified Philips colour TV which was
powered via a special socket on the Viewdata set. This connected to a
secondary winding on the Viewdata set's mains transformer (giving about
100V IIRC), this provided the isolation.
The other, of couse was the US version of the origianl TRS-80 Model 1
monitor. This was a converted RCA portable TV. The modification involved
replacing the IF amplifier PCB with an opto-isolated board. The monitor
chassis remained 'hot'. This monitor needed a 5V suppy from the computer
to power the LED side of the opto-isolator.
FOr the record, the European version of this monitor was not hot-chassis.
It had the same chassis run from a 250V - 115V _isolating_ transformer
inside the case. The IF PCB was replaced by a simple video amplifier.
-tony