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Apple colour monitor not showing colour

Dutch,

Your query triggered some brain cells and I THINK has solved another puzzlling issue I had. See what you think.

Anyway, getting back to this thread, here are the details of my GOOD Apple IIe machine (now that I figure one of them has the wrong IOU IC in it..see under the link above).

This machine shows a nice colour image on my 240v Apple colour monitor, but only a monochrome image on the 110V machine:

The details are:
On the IOU - AMI 8623MBs 344-0022-A Apple 82 Philipines.
Written on the circuit board - Apple IIe International NTSC - Apple Computer 820-0188-C
Rev B-607-0288-C

I can't see anything that tells me the clock frequency. I can see only one Crystal on the board and that says :

-0002
5H
197

..does that mean anything to anyone?

I have a feeling vwestlife is right and these machines put out some wierd kind of hybrid NTSC signal but for 50Hz rather than 60hz? NTSC is written on the board rather than PAL. Certainly I've never got colour out of them except on the 240v Apple colour monitor.

Tez
 
I have a feeling vwestlife is right and these machines put out some wierd kind of hybrid NTSC signal but for 50Hz rather than 60hz? NTSC is written on the board rather than PAL. Certainly I've never got colour out of them except on the 240v Apple colour monitor.

Tez

I tend to agree. According to this, http://www.8bit-museum.de/docs/toolshtml2.htm, the 344-0022A was supplied in the 50 MHz PAL motherboard.
 
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I don't know if this has being mention yet, but the apple monitor having an NTSC system is touchy on the OSC Freq of the main board, if you are not getting color, start the computer and remove the lid, and with a plastic screwdriver, adjust the OSC cap, its a little variable cap on one of the corners, its being a long time since i've touched an apple PCB, so i can't exactly remember where it is, but its on the main board near one of the corners, just give it a little turn in both directions, you should get color.
 
It sounds like it might be a match to this crystal:
http://www.willegal.net/appleii/forsale/pal-crystal.jpg
which is 14.025 MHZ and intended for PAL systems. The color burst it generates is not close enough to NTSC standards for monitors to lock onto the color burst. If you substitute this vishay/dale crystal, it "may" work.
XT9UNLANA14M31818


regards,
Mike Willegal


Dutch,

Your query triggered some brain cells and I THINK has solved another puzzlling issue I had. See what you think.

Anyway, getting back to this thread, here are the details of my GOOD Apple IIe machine (now that I figure one of them has the wrong IOU IC in it..see under the link above).

This machine shows a nice colour image on my 240v Apple colour monitor, but only a monochrome image on the 110V machine:

The details are:
On the IOU - AMI 8623MBs 344-0022-A Apple 82 Philipines.
Written on the circuit board - Apple IIe International NTSC - Apple Computer 820-0188-C
Rev B-607-0288-C

I can't see anything that tells me the clock frequency. I can see only one Crystal on the board and that says :

-0002
5H
197

..does that mean anything to anyone?

I have a feeling vwestlife is right and these machines put out some wierd kind of hybrid NTSC signal but for 50Hz rather than 60hz? NTSC is written on the board rather than PAL. Certainly I've never got colour out of them except on the 240v Apple colour monitor.

Tez
 
It sounds like it might be a match to this crystal:
http://www.willegal.net/appleii/forsale/pal-crystal.jpg
which is 14.025 MHZ and intended for PAL systems. The color burst it generates is not close enough to NTSC standards for monitors to lock onto the color burst. If you substitute this vishay/dale crystal, it "may" work.
XT9UNLANA14M31818

regards,
Mike Willegal

Thanks Mike. Just to be clear though, you are talking about replacing the Xtal in the computer, right? However, this issue in this thread is my 115V Apple Colour Monitor. All five working Apples (and clones) show colour just fine on my other Apple Colour Monitor, which is for 240v. It is the 115V U.S. sourced monitor which isn't showing colour.

If it does require a Xtal change in the computer to get this U.S. monitor to show pretty pictures, I'll just accept it will only ever be a monochrome display.

Tez
 
It's my guess that your computers are likely to be running at the 14.025 MHZ PAL frequency, which works with the 240 volt international monitor, but not with the 115 volt US monitor. There is almost no frequency margin in locking in on the NTSC color burst on a US monitor. I've had an awful time finding the right 14.31818 MHZ crystal that would generate the right color burst in an A2 or A2+. You could swap the crystal in the computer's, motherboard as temporary test to verify my guess.
 
Right. Yes, that makes sense.

Before I owned all these Apples I was impressed that the Apple II was a colour computer, when colour seemed such a difficult and expensive thing to implement in the late 1970s.

Now I know how Woz did it, I'm even more impressed by the sheer trickery. As you say though, such trickery means tolerance levels are probably low.

Tez
 
I don't know if this has being mention yet, but the apple monitor having an NTSC system is touchy on the OSC Freq of the main board, if you are not getting color, start the computer and remove the lid, and with a plastic screwdriver, adjust the OSC cap, its a little variable cap on one of the corners, its being a long time since i've touched an apple PCB, so i can't exactly remember where it is, but its on the main board near one of the corners, just give it a little turn in both directions, you should get color.

I thought this as soon as started reading the thread.

From the front, it's on the back right of motherboard near what looks like a "light-pen" connector.

You may be able to trim it just enough...

You can't hurt anything and can always re-adjust it on the 240V monitor.
 
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