🚀 go-pugleaf

In article <B166BA09966833DDD@0.0.0.0>,
terry@edgy.demon.co.uk (Terry Bishop) wrote:

> On behalf of a friend, can anyone say what the chances are of hooking up an
> old 19-inch monitor to a new Mac or clone? Options are a G3 or the UMAX
> Pulsar 180 with the 604e chip.
> 
> The monitor in question is an IKEGAMI C/T-20HA REV C dated 1990. It has a
> normal 2-row 15-pin Mac cable on it (which would need to be changed to a
> 3-row) but I don't think that's the problem -- he's been told that it may
> not synch.
> 
> Any advice gratefully received. TIA.

The model of Mac makes little difference, thankfully the days of
short-sighted marketing people deliberately crippling the video support are
long gone.

First of, you will NOT have to change the connector, the two row 15pin
connector IS the correct one for a Mac - if you change it to a 3row HD
15pin connector then you will need an adapter to change it back (though
ISTR the Umax does have an HD connector but supplies an adapter).

I'm pretty sure I know the monitor (we used to have one in our showroom
when I was in business, and for it's day was an excellent monitor), but I
don't know the specs. The version we had (similar year to yours) was set up
at 60Hz, though a lot much later version did 75Hz.

Looking at the tech info for the G3 (we installed three last week,
unfortunately none of them was mine ;-(   ) I see that there is a 1024x768
mode at 60Hz vertical, and also at 70 and 75Hz - the latter is the "19inch
colour" monitor setting.

Unfortunately, in this sort of situation there is no alternative than suck
it and see - and the use of a good multisync is invaluable.


The way I suggest you tackle the issue is as follows :
Check the existing cable and see if pins 4, 7, and or 10 are connected
either to ground (several pins) or each other. If the cable is a similar
vintage to the monitor, then it is highly unlikely that there will be any
diodes involved ...

In all of the next steps, you will have to go inside the monitor and adjust
some controls. The ones you are looking for are probably labelled
"Horizontal Frequency" and "Vertical Frequency" or some sort abbreviation
of these. I would guess that on removing the outer plastic cover, you will
find a complete perforated metal case which will have access holes for the
controls. When adjusting the controls use insulated tools as some of them
may well have high voltages present, and you may find some that need a
specially shaped tool (typically hexagon) to turn a ferrite core*.

If any of these pins are connected, try the monitor with its cable "as is"
and see what happens. If you see any video at all try adjusting the monitor
to suit.
Next I suggest making up an adapter of a 15pin plug to 15pin socket with
all pins connected except 4, 7, and 10. You can then try different
connections for these pins. Unfortunately I don't have that information to
hand (it is at home), but if you don't have it then email me.
The next setting to try is for a 19" monitor, then a 20" mono, then VGA.
For VGA, you really need a good multisync so that you can set up a
resolution, then try the Ikegami.

I have successfully configured a colour monitor similar to yours as a VGA
but it does have problems ! First, the monitor is NOT multisync, so if the
Mac reverts to a 640x480 display then you will lose the picture - to
restore it you will need a VGA multisync monitor so that you can see the
screen while you reset the resolution. Secondly, there are a number of
situations where the Mac WILL change resolutions - these include: starting
up from another disk (eg floppy), starting up without the monitor attached
(or with another monitor attached), or IIRC resetting the PRAM may affect
it.


TTFN, Simon

* A ferrite core is simply a slug of sintered iron, normally threaded on
the outside to allow it to be screwed into a plastic housing. Adjustment of
these is by screwing it into or out of the coil surrounding it, and it is
important to use a non-metallic tool which fits the hole down the middle
and is at least as long as the core. If you try turning it by one end it
may break.