Strange board on Mac 512k

[Jelly]

Hi,

Yesterday I picked up my first 512k. They are hard to get in Europe so I had to pay a whopping 20 euro for it ;-)

But, on boot no glory. I opened it up and after scanning the molded autographs (yes!) of the creators, I picked up a service source manual to see what was going on inside. But my 512 k did not only have a logic board on the bottom and another board on the right, but also one on the left. No serials, no inscriptions, just IC's and some connectors. The connector from the standing board on the right was disconnected from the logic board and connected to the alien board and from there reconnected to the logic board. From the alien board 2 other connectors could be found: something that looks like the mouse-connector from this Mac (also the modem/printer connector) and one connected with two small pins to a cable guided outside the Mac with on the end 2 audio-like plugs, like the ones you find on your old record player.

I can't post pictures here, but if you want a picture, please notify me.

Disconnecting this board resulted in a booting Mac, but now I need to make a boot floppy. How does that work since I only have 800k floppies? I checked the floppy-drive inside and it is definitely a 400k model. My SE/30 only seems to initialize floppies to 1,4MB (?), also really odd in system 6 is my guess...

Kind regards,

Jelle

 

[Mars478]

Post pictures to imageshack and then embed them here.

For a start you may want to remove the extra board.

 

[Dog Cow]

Your SE/30 should be able to format an 800k disk as single-sided 400k format with System 6 or 7.

 

[Jelly]

Hi all,

Thanks for your replies.

Here a URL with a picture, hope it works: http://img43.imageshack.us/img43/3598/img0659j.jpg

or

http://yfrog.com/17img0659jj

What program should I use on the SE30 to format an 800k floppy to 400k MFS? Or burn a system 2.0 image to an 800k floppy... This is such old technology, I lost all my knowledge over the years and the internet just seems to think I recall all the necessary steps...

Thanks all,

Jelle

 

[H3NRY]

That's a most peculiar board. There are RAM chips it looks like, and it takes power from the MB power connector. Could it be a video card designed to drive a standard 9-pin CGA monitor or a TV monitor thru an RCA jack? I've never seen anything like it. 8-o

 

[Mac128]

Give THIS LINK a whirl. Just about everything you need to know well written should help you.

Is this a 240V M0001WP European model? Or is it a 120V North American model?

H3NRY, if 240V European, could this be a PAL converter? I seem to recall the Apple II had quite a problem with that as well.

 

[H3NRY]

could this be a PAL converter?

It could, but it could just as well be an NTSC converter. Since Macs have their own display, there's no native NTSC or PAL video capability. I have seen a few people who did user group demos all the time who had a TV projector, back before computer projectors were common, and they had scan converters to drive their displays. Usually external boxes, though some means of tapping the video signal inside the Mac was needed. We designed one at Beck-Tech called the Chromatron which drove a standard NTSC monitor in color from a 128K/512K or a Plus, but it was an external box with its own power supply. It had a 9-pin output to drive a standard IBM / Amiga TTL RGB monitor and a composite NTSC RCA output.

Since Apple][s used TV sets for displays, they had to have different circuitry for PAL and NTSC. Early Macs are unique, not compatible with NTSC, PAL, MDA, CGA, PGA, VGA or any other format.

 

[Mac128]

Ah thanks for that H3NRY, that's right the first Apple ][ only had an NTSC output, that's why PAL was such a headache.

I agree the board is most likely an internal scan converter if only because it has that 9-pin connector for a monitor as well as two RCA outputs. Do you think it also handles sound, hence the second RCA, or it has dual video outputs? The sound is carried through one of the pins on the power connector, so the board has access to both.

Love that the adapter you were involved with drove a color TV set. Could the Mac with this adapter take advantage of color in any way?

 

[Trash80toHP_Mini]

A larger pic w/higher contrast so the chip designations are clearly legible would be a big help. Given that, and a good solder side pic, we'll be able to learn all there is to know about the hardware end of that card.

No markings on a two sided board (no ground plane) with that kind of trace layout, screams "prototype" to these old TTL Cookbook era ears/eyes!

:?:

 

[Bunsen]

A larger pic w/higher contrast

Or a scan

 

[H3NRY]

Could the Mac with this adapter take advantage of color in any way?

Yes, it could. I designed it so the pixels were clocked out at 14.31818 MHz with color burst like an Apple II, thus turning MacPaint fill patterns into colors. ChromaTron, see? :lol:

 

[Jelly]

I will make new, more and better pictures this weekend. Your speculations make me curious too. Even though I have always been wondering what the advantages of NTSC were/are, next to the existence of PAL (or even SECAM) it does sound eligible that the board has got something to do with a second monitor for this Mac. Checking the markings on the various chips on the board leaves me helpless on either a chinese website I can't read or stuck in a very technical environment: I am not a techie...

Hope you guys will check my next posting also. Thanks.

Jelle

 

[Mac128]

There are no advantages to NTSC over PAL. PAL is better in almost very way. Better refresh rate, better color resolution, better line resolution and no conversion problems between film and video which result in judder in NTSC systems.

 

[Paralel]

Negative on the refresh rate, it is lower than NTSC.

 

[Jelly]

Here a link with new and better photo's:

http://img638.imageshack.us/g/img8261r.jpg/

Thanks for looking and I look forward to your thoughts.

Jelle

 

[Paralel]

That is a weird board. That big plug which just loops back into the receptacle right next to it is just strange. However, with those two mini-jacks coming off of it I'd venture a guess that it is meant to hook into an Apple II or something like that, since they look like the pair of mono in & out one could hook into an Apple II for cassette support.

 

[Mac128]

That big plug which just loops back into the receptacle right next to it is just strange.

Not strange at all. When the board is in use, that is the standard 10-pin power and data plug that goes from the logic board to the analogue board. Like many adapters of this type, it instead goes from the analogue board to the alien board, then to the logic board. It routes, in particular, video and audio.

How exactly would such a board have worked between a Mac and an Apple II? I never heard of such a thing before.

My money is still on video output now that I see they are male RCA plugs. One video, one audio and one TTL.

Negative on the refresh rate, it is lower than NTSC.

Yes of course, 50Hz vs. 60Hz. However is that still a consideration with LCD? Film is 24 frames. PAL is 25 frames, and NTSC is 30 frames. In terms of video fluidity, 30 frames will be smoother. But in practical application 24 frames is pretty smooth and what we watch all films at on LCDs. I'll take the added resolution and reduced judder on a PAL CRT any day. On LCD though, I suppose it doesn't matter anymore especially since color is digital and that was the main advantage of PAL aside from resolution. In which case, more frames would be better for sports, so NTSC has a slight advantage now for that.

 

[Paralel]

NTSC also has the advantage with newer sets that are either 120 or 240hz being an exact multiple of 30 and 24.

 

[H3NRY]

My money is still on video output now that I see they are male RCA plugs. One video, one audio and one TTL.

I'll go along with that - mostly. It looks to me like the RCA cables terminate in a 2-pin plug at the mystery board, so my guess is they are wired together and bring the (mono) sound out to a stereo amplifier. The 9-pin plug is probably video for a TTL RGB monitor / projector, so neither NTSC or PAL. I'm still guessing - I haven't traced out the circuit or anything, but the chips on the board would be consistent with such a scan converter. It also looks very prototypish.