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Mac 128K with SAD MAC error 041800


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  Mac 128K with SAD MAC error 041800 by Bill Degnan - 09/13/2007 11:43
yes, but what does 041800 mean exactly? which chip or section is bad?

04 = class code = memory test mod 3
1800 = chip identification codes, in binary combination
1000 is bit 12, chip G9
0800 is bit 11, chip G8

Need two 4264 chips, to replace G9 and G8.

Thanks Herb.

  Mac 128K with SAD MAC error 041800 by Bill Degnan - 09/27/2007 12:37
Follow up...I got a new motherboard for this system.

  Mac 128K Repair by Bill Degnan - 09/30/2007 13:46
There are 5 screws to remove before one can slide the Macintosh 128K cover from the chassis. The elusive 5th screw is under the AA battery cover.

After removing the cover, the motherboard is very easy to remove from the chassis. Simply disconnect the power and data cables and slide the motherboard out of the slot. I purchased a replacement board from Vintage Micros -

Here are some updated pictures.

  Flattened Horizontal by Bill Degnan - 04/27/2016 08:41
MacIntosh 128K
This photo shows the contents of the external boot diskette. The internal drive is stuck and will need repair or replacement. Click image for larger view.

The motherboard is working fine 8 years since last testing but more work remains to be done.

Horizontal screen display flattening MacIntosh
The screen occasionally shrinks horizontally, indicating a faltering cap or related part within the display unit hardware. Click image for larger view.

Most of the time the display is fine. Click image for larger view.

Ian P says:
"...The 128 uses a pair of discrete transistors for it's vertical driver.
If one of the caps in that circuit has failed/is failing, I'm guessing
it's C6. Or it's either C5 or C11. While you're in there,
be sure to resolder the yoke connector, it's a very common point for
cold solder joints (will cause total loss of deflection)

If it's intermittent (i.e., you can hit it and it pops back), it's
probably just a bad solder joint. Resolder Q1 and Q2, and nearby
components, as well as the yoke connector. If it starts out bad and
gets better as it heats up, or starts good and gets worse as it heats
up, and hitting it doesn't affect it, then, it's definitely one of
those caps.


New photos

  Analog Board Repair by Bill Degnan - 11/29/2018 09:19
Apple Macintosh Analog Board Vertical driver failing
Image showing the vertical driver causing image compression before repairs. Click image for larger view.

Apple Macintosh analog board C5
Closeup of analog board location of failed 47uF capacitor C5. I replaced the original 10V cap with a 35v cap of the same uF. Click image for larger view.

Repair completed. Click image for larger view.

Note, I also removed the disk drive and relubed it.

  Bad internal Drive Seek by Bill Degnan - 11/29/2018 21:20
Fixed one thing and a new issue popped up. The drive now jumps to track 0 and bangs against it, never finds where it needs to be. I guess a sensor is bad. I have more notes will get back to this, someday.



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