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Apple IIc keyboard and display issues

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Neo-Rio

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Joined
Feb 13, 2016
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Recently brought an Apple IIc back from the dead with a new power regulator chip, but now I have a few new problems.

Essentially, the keyboard allows me to do control+apple+reset and reboot the machine, as well as break out of loading from the disk drive.... but any other keys just do not function at all. I entered BASIC, but none of the keys are printing anything to the screen.

Additionally when running a self-test the screen seemed to shake left and right like crazy. Eventually I got a System OK message however. I tried loading up a disk and the display I got from it was also shaking like mad.

Also, how does one get the Apple IIc to display in colour?

Thanks
 
Neo-Rio said:
Recently brought an Apple IIc back from the dead with a new power regulator chip, but now I have a few new problems.

Essentially, the keyboard allows me to do control+apple+reset and reboot the machine, as well as break out of loading from the disk drive.... but any other keys just do not function at all. I entered BASIC, but none of the keys are printing anything to the screen.

Additionally when running a self-test the screen seemed to shake left and right like crazy. Eventually I got a System OK message however. I tried loading up a disk and the display I got from it was also shaking like mad.

Also, how does one get the Apple IIc to display in colour?

Thanks
Click to expand...

Keyboard encoder chip could be bad, ctrl-reset and apple keys bypass the encoder so would not be affected.

For the display issues, I assume from your British-English use of "colour" you are probably in a PAL region? If that is so, and you happen to have an NTSC region //c, there might be your problem, can you post a photo of your //c, top and bottom, we can help narrow down which one you have.
 
RWallmow said:
Keyboard encoder chip could be bad, ctrl-reset and apple keys bypass the encoder so would not be affected.

For the display issues, I assume from your British-English use of "colour" you are probably in a PAL region? If that is so, and you happen to have an NTSC region //c, there might be your problem, can you post a photo of your //c, top and bottom, we can help narrow down which one you have.
Click to expand...

It's a PAL unit. I'm actually connecting the video through composite to TV. Color works fine when I do this with my apple IIe. The IIc stays black and white, and judders when graphics is on the screen, or I run the self-test. It's OK with just text.

Is the keyboard encoding handled by the 3600-PRO chip?

Don't have a scope, sorry. Not likely to get one soon either.
 
Hmmm - wait a minute, there is a -11V supply that goes to the keyboard encoder, floppy ports (which may not be used) and serial ports. That -11v gets regulated to -5v and goes to the video encoder !!!
Check those voltages !!!
 
retrogear said:
Hmmm - wait a minute, there is a -11V supply that goes to the keyboard encoder, floppy ports (which may not be used) and serial ports. That -11v gets regulated to -5v and goes to the video encoder !!!
Check those voltages !!!
Click to expand...

Where do I check for these?
The 5v should be off that 5v regulator near the keyboard encoder, right?

I am getting a little over 5v on the rightmost pin of that 7905 regulator... so it seems OK to me.
 
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ok for starters, if you don't have the manual, google "sams computerfact apple iic" take the 2nd link to archive.org then below is an option to download as pdf.
Page 3 right in middle of page shows the source. Yea it looks like the -5v is an off board regulator, and the input pin is -11v or so, correct? Also make sure those are
getting to points on the board shown in the sams
 
In my Apple IIc this 7905 was defunct also, it emitted anything between -6 and -11 Volts, replaced it and the screen stability improved a lot. Furthermore: a bad (original) videocable cause also some waviness on screen due to the monitor and the Apple being grounded through their mains cables. Replaced it by a better one and the screen was rocksolid.
 
yea that's why I'm asking the OP to verify the -11V input to the regulator because the -5V out could stay stable but the -11V input could get sucked down as you say to maybe -6V which would affect the keyboard encoder.
 
Neo-Rio said:
It's a PAL unit. I'm actually connecting the video through composite to TV. Color works fine when I do this with my apple IIe.
Click to expand...
A PAL unit won't display colors using the composite output. You have to get a PAL modulator (see here for more information) or a Chat Mauve SCART cable like this one.
I'm pretty sure your //e is a NTSC one, right ?
Using a multistandard TV, you will get colors with the composite output.
 
retrogear said:
yea that's why I'm asking the OP to verify the -11V input to the regulator because the -5V out could stay stable but the -11V input could get sucked down as you say to maybe -6V which would affect the keyboard encoder.
Click to expand...

Well, the leftmost pin of the 7905 is getting nothing at all.
The middle pin is getting -11.85V


Perhaps I should be looking at the input pin of the keyboard encoder?
I measured pin 27 on that chip for -11V and got it
Measured pin 30 for 4.9V and got that too.
 
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left pin is ground so will be 0v. middle pin should be negative 11v and right pin negative 5v. It would be nice to confirm the negative 11v at encoder IC pin 27 if you can reach it and +5v at pin 30. Pin 16 is the strobe normally 0v but pulses to 5v with a keypress.
Measure pin 16 while holding down a letter key to make it auto repeat. You should see maybe 1 or 2 volts while keeping the key pressed
 
retrogear said:
left pin is ground so will be 0v. middle pin should be negative 11v and right pin negative 5v. It would be nice to confirm the negative 11v at encoder IC pin 27 if you can reach it and +5v at pin 30. Pin 16 is the strobe normally 0v but pulses to 5v with a keypress.
Measure pin 16 while holding down a letter key to make it auto repeat. You should see maybe 1 or 2 volts while keeping the key pressed
Click to expand...

As mentioned, I did get the correct voltages off pins 27 and 30 on the keyboard decoder chip.
However pin 16 is getting nothing, even after keyboard presses.

The question then becomes.... is the keyboard broken, or has the keyboard encoder chip broken?

I'm going to replace the keyboard encoder chip anyway. Fortunately spares are easy to get.
 
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Replaced the keyboard encoder chip with a new one and viola.... the keyboard comes back to life.

Now for the shaky display. It seems to be flipping between colour and B/W modes out of control. Any ideas as to which chip has hit the skids?
 
Went through this on another forum. The master oscillator crystal could be the culprit. On a IIc is a rectangular metal can with the frequency stamped on it.
PAL is 14.24982 MHz part# CK0044AC. If you want to confirm, you can try cooling it with an ice cube in a double ziplock bag. For that user, the color returned.
Part might be available here:
http://prismelectronics.net/index.php/catalogsearch/advanced/result/?sku=ck0044ac
 
retrogear said:
Went through this on another forum. The master oscillator crystal could be the culprit. On a IIc is a rectangular metal can with the frequency stamped on it.
PAL is 14.24982 MHz part# CK0044AC. If you want to confirm, you can try cooling it with an ice cube in a double ziplock bag. For that user, the color returned.
Part might be available here:
http://prismelectronics.net/index.php/catalogsearch/advanced/result/?sku=ck0044ac
Click to expand...

The screen shaking only happens when the display is in some graphic mode. No problem when the screen boots and I get the Apple //c screen or Basic prompt.
The screen shaking starts up during a self testimage.jpg ... and if you can imagine that display shaking left and right by about half a centimetre very quickly, then that is what I am seeing.

I'll have to keep an eye out for the part. Seems to be quite rare.
 
Master clock still could be the shaking issue. The horizontal and vertical scan rates are divided off that clock. Just depends how far off frequency it is.
Otherwise, it could be how sensitive the display is to the sync signal. Might need to confirm on another display?
 
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