General Stuff(tm)

[stephen_usher]

Looking into this more and reading about the PX-4, it's very much a cut-down PX-4 in a handheld format. The interface at the top for expansions is the same as the module interface on the PX-4 but with a different way to lock the modules in place (screws vs. a catch mechanism).

Looks like the PX-4 would be used as a development environment and software uploaded into the battery backed RAM disk or burnt onto an EPROM.

[stephen_usher]

Finally got around to building one of my Mac II (composite sync) to VGA (separate sync) boards tonight. It was a fight with the tiny pitched SMD LMH1980 chip, with added problems of the bodge wire. Lots of swearing happened.

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Well, less than successful. Firstly, still doesn't work with the built-in video port on the IIci, only the Mac II video card.

But... The display is blue and the horizontal sync timing is all over the place. The display also thinks that the number of scan lines is far greater than there are. Hmmm... Oh, and it's powered via the ADB port, which doesn't work any more... maybe pulling too much current.

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So, as an experiment I thought I'd verify that the Samsung telly couldn't display the output from the Mac II video card as it hadn't previously... But with the different VGA cable... It worked. *sigh* So I have no need for the splitter anyway.

P.S. I've just had a thought... Maybe I had the monitor ID links wrong and the card thinks that it's a portrait monochrome monitor! Hence double the vertical resolution and only one colour channel!

[stephen_usher]

I think that I've worked out one issue... I'm using the wrong wires from the ADB/S-Video lead to power the board. I'm actually using the power-on wire and data wire for 0V and +5V instead of the ground and +5V wires. D'oh!

This will mean that the "ground is either floating or above 0V and the data wire will be held high. I'll rewire tomorrow and see what happens.

[rubber_jonnie]

I think that I've worked out one issue... I'm using the wrong wires from the ADB/S-Video lead to power the board. I'm actually using the power-on wire and data wire for 0V and +5V instead of the ground and +5V wires. D'oh!

This will mean that the "ground is either floating or above 0V and the data wire will be held high. I'll rewire tomorrow and see what happens.

Ahh, oops!

[stephen_usher]

Bother! I can't use the S-Video cable as although it's got four core in the cable, red, black, brown and unsheathed the brown wire isn't actually connected and the two ground wires are shorted inside the moulded plug! This means that the power-on pin and the data are continuously connected when plugged into the ADB port. *sigh* Why did they have to do that rather than use the brown wire? The luminance and chrominance are supposed to be fully separate, including grounds, for a reason.

I'm going to have to source a mini-DIN plug.

[stephen_usher]

Bother! It looks like all the pin-outs of the Mac II video connector online are actually wrong!

They count the pins in the wrong way relative to the connector from what I can make out, so my PCB is completely useless.

[PhilC]

What cable pin out is it you need? I’ve managed to get an LC-II to VGA working but after some searching.

[stephen_usher]

It's for a IIci, which is basically the same. The signals, however, don't seem to tally with the pin-out diagrams I've seen, with the pin numbering not matching what I see on the port.

[PhilC]

It's for a IIci, which is basically the same. The signals, however, don't seem to tally with the pin-out diagrams I've seen, with the pin numbering not matching what I see on the port.

Okay, I’ll show you what I have later on.

[PhilC]

hi @stephen_usher

here's the pinouts I used. (just typing it up on my Mac first and will then send a photo from my phone as to how I did it.

So these are both from the perspective of the back of the plugs being used. (see photo lower on).

15 pin Mac 15 pin VGA
1 6
2 1
3 NC
4 NC
5 2
6 7
7 to Mac pin 10
8 NC
9 3
10 to Mac pin 7
11 NC
12 14
13 8
14 10
15 13
GND to GND
Because of my dodgy shaking hands and the fact that you sometimes need to mess about to get cables right I decided to use these plugs that I got from Amazon to make up my test cable. I’ll make up a soldered cable soon.

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