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? http://docs.info.apple.c...rticle.html?artnum=7748 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. Reply
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. Reply
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 - http://vintagemicros.com/ Here are some updated pictures. Reply
Flattened Horizontal	by Bill Degnan - 04/27/2016 08:41
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. 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. -Ian..." New photos Reply
Analog Board Repair	by Bill Degnan - 11/29/2018 09:19
Image showing the vertical driver causing image compression before repairs. Click image for larger view. 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. Reply
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. Reply