22 Apr
2007
22 Apr
'07
9:45 p.m.
On 21 Apr 2007 at 23:30, Jim Leonard wrote:
There wasn't. I'm in Europe (and have 50Hz mains), I also have an IBM CGA
card. It's just like the one in the Techref, it takes all the timing from
the 14.xxx MHz oscillator on the mainboard.
If the entire system was designed around the NTSC
frequency (and one
would assume the 60Hz AC power to match) then how did a "euro" IBM PC
work? Did it have 60Hz CGA as well?
I believe so, unless there was a very different CGA card for Europe.
If there was, the Tech Ref is completely silent on the subject.
BTW, when we asked if the 5150 could simply be run from a 220V-120V
50Hz stepdown transformer the answer came back quite emphatically:
"No, you cannot--and if you try, it will void the warranty." I
I can't comemnt on the second part, but for the first part I will say
that whoever told you that was a total idiot. Period...
There were, I admit, several types of PSU used in the 5150 (and related
machines), and they were made by various companies. The schematics aren't
in the Techrefs, but I've been inside a fair frw of them and _not one_
would ogject to 50Hz mains of the appropriate voltage. Most of them do
insist on AC, since they have a little mains-frequency transformer to
provide the startup supply to the SMPSU, but that would work find on 50Hz
mains.
The 5105 Techref _does_ imply that the 115V PSU is for 60Hz mains and the
230V one for 50Hz mains, but I can see no good reason why that would be
the case. The 5160 Techref contains the IMHO meaninless spec of '50/60Hz
+/- 3Hz'
The 5155 (Portable PC) PSU is electrically similar to the supplies I've
found in PCs and XTs, and was user-selectable (slide switch on the back)
betweem 115V and 230V mains, and needless to say it works fine on 50 or
60Hxz. The other system PSUs that I've seen (and remember I've only seen
supplies used in 230V machins) have intneral lings, in general 'fitted
for 115V, cut for 230V' to set the voltage.
pressed the sales people for specifics and they said
something about
"the power supply won't allow it". AFAIK, the only line-frequency
dependent part in the PSU was the AC fan--and 50Hz probably wouldn't
have made a difference.
Actuaally, all the fans I've seen have been 12V DC ones, oftne run off the
-12V rail
-tony