Re: Problem Using a Commodore 1084s Monitor on a IIgs

[heuser.marcus@freenet.de]

Polymorph wrote:
>
> Because of this I picked up a Commodore 1084s monitor off of eBay to
> use as a replacement. I have tested the monitor with a DVD player and
> the image produced was quite good, so I know the monitor is working.

Via composite or via RGB?

> However, I wired up a cable as per the Apple II FAQ over the weekend
> and had troubles getting the monitor to synch with the RGB signal. The
> image just kept scrolling all over the place.

This really sounds like a sync problem.

> I tested the cable, and everything seemed to be wired correctly.
>
> In an attempt to fix the problem, I tried:
> (i) to wire the IIgs's composite synch to the horizontal synch
> (ii) switch the monitor between 50Hz and 60Hz
>
> None of the above made any difference.
>
> One thing I should note is that just about everywhere lists the 1084
> monitors D-9 RGB connector as being female, however in the monitor I
> have it is male. Consequently, my cable has a female D-9 socket. I
> have made the assumption that the wiring would still be the same (i.e.
> pin 1 mentioned in the A2 FAQ is pin 1 on my monitor). This seems to
> be true as I do not think I would get the image that I am getting if
> it were incorrect. It just seems to not be synching with the signal.
>
> So I did some snooping around in the c.s.a2 newsgroups looking for
> threads on using 1084 monitors with the IIgs. I found a post by Jeff
> Blakeney in the mid-1990's mentioning the usage of a 75 Ohm resistor
> wired between the composite synch and ground to alter the voltage to
> more acceptable levels for the 1084 monitor. Most other posters using
> a 1084 don't mention any requirement for doing this, and the Apple II
> FAQ doesn't mention it either.
>
> To gauge the likelihood of success, has anyone else had to use a 75
> Ohm resistor in this manner to get a 1084 to synch with the IIgs?

For a PAL monitor you don't need to do this.

> Is there anything else I can try to get the image to synch?

The standard way for a GS to connect to a PAL 1081/1084s
(the 1081 has mono sound, while the 1084 is stereo) is to use
its Euroscart input with its analog RGB leads.

Pin 3 ("composite sync") of the GS video output jack must be
fed into the composite video input of the Euroscart connector
(pin 20).

There is more to do with this type of connector - this page
details the pin to pin connections:
http://vintageware.orcon.net.nz/apple2/scart.html

Here you can download the PAL schematics of the 1081s which
may or may not be of help (be cautious because of the differences!):
http://rapidshare.de/files/38368884/Monitor_1081.zip.html

I would try to connect pin 3 of the GS output to the composite
input of your monitor.

If this doesn't work it could be a "sync-on-green" problem but
I'm not really familiar with this. I only wanted to throw this into
the room so somebody else can jump into it (or discard it).

HTH,
Marcus