80 column mode and a 1084S-D2

[gdanko]

My monitor is a 1084S-D2, the kind with the power button in the back. It has a DB9 RGB connector on the back and the usual array of female RCA jacks. I plugged my C128's video DIN jack to the RCA jacks on the back and I can get 40 column mode. If I plug the DB9 cable from the back of the C128 to the back of the 1084 and reset to 80 column mode I can see the screen but it rolls and I cannot adjust it. There is no vertical hold adjustment anywhere on the monitor. Could it be a defective cable? The monitor has almost no use its entire life so I have a hard time suspecting it. One last note, I tested everything on a C128D and got the same results. Any help is appreciated.

[Mangelore]

Is there a Analog/TTL switch on the back of the monitor? Make sure it's in TTL mode.

[Andrew Wiskow]

gdanko, I have this exact same model of monitor, and it has the exact same problem when attempting use 80 column mode with a C128.  I suspect that the RGB connection on this model is only for Amiga.

Mangelore, no, there isn't an Analog/TTL switch on the back of the monitor on this monitor.  There are only two switches on the back, one for CVBS/LCA and one for CVBS/RGB.  Again, I suspect that this model was designed for Amiga use only.

-Andrew

[airship]

The online manual for the 1084S talks about the Analog/TTL switch. For RGBI mode, it says:

Set the ANALOG/TTL switch to TTL mode.  Set the CVBSIRGB switch to RGB mode.

I had no idea that there was a "D2" model without this switch. I suspect you're right Andrew - at some point CBM must have decided that C128 support was unnecessary and changed the 1084 design to Amiga-only to save 25 cents, screwing C128 owners in the process. Surprise.

[StyleCHM]

if the picture is good, but it just rolls, then obviously only the vsync signal is missing somewhere.

dont quote me, but I seem to recall the 128 doesnt use a seperate vsync signal.... maybe sync on green? If the D2 expects the seperate sync signal then you might need to seperate it out with a small circuit, or perhaps its the other way and you need to combine them......

[Mark Smith]

if the picture is good, but it just rolls, then obviously only the vsync signal is missing somewhere.

dont quote me, but I seem to recall the 128 doesnt use a seperate vsync signal.... maybe sync on green? If the D2 expects the seperate sync signal then you might need to seperate it out with a small circuit, or perhaps its the other way and you need to combine them......

Nah .. before my 1084 blew up it would roll the screen if Analog was selected rather than digital.

Mark

[Mangelore]

The online manual for the 1084S talks about the Analog/TTL switch. For RGBI mode, it says:

Set the ANALOG/TTL switch to TTL mode.  Set the CVBSIRGB switch to RGB mode.

I had no idea that there was a "D2" model without this switch. I suspect you're right Andrew - at some point CBM must have decided that C128 support was unnecessary and changed the 1084 design to Amiga-only to save 25 cents, screwing C128 owners in the process. Surprise.

I recall once using a 1084S monitor that would only accept the Amiga Analog RGB signal. The digital TTL RGBI was missing.
Unfortunately, I don't have it anymore to check if it was a -D2 model.

[smf]

dont quote me, but I seem to recall the 128 doesnt use a seperate vsync signal.... maybe sync on green? If the D2 expects the seperate sync signal then you might need to seperate it out with a small circuit, or perhaps its the other way and you need to combine them......

I believe it's composite sync, this circuit might be able to do the job: http://www.nexusuk.org/projects/vga2scart/circuit

However, you could also just try wiring the mono composite out ( rgbi pin 7 ) to the csync in ( 1084 pin 7 ). This signal has the syncs and the video combined, but the monitor will ignore the video and just use the syncs. Thats the theory anyway. On SCART connectors the sync comes from the composite video line too.

To get colours working better then you can try this circuit: http://www.softwolves.pp.se/cbm/maskinvara/scart.en.html

[Mark Smith]

The RGBI connector has seperate horizontal and vertical syncs outputs.

You'd need to combine them to get composite sync if you wanted to connect to SCART (as well as converting the digital RGBI to anlaog), I've done what I think is a schematic to do it but I've not built it yet ... combination of being lazy, fixing the house, having twins inbound and not having any components to hand yet :-)

Still .. maybe with my nice new FPGA board I can do a RGBI to VGA ;-)