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Macintosh Portable, what is R21 resistor value?
Posted by: gijsmans on 2020-07-16 23:29:57
I am restoring a Macintosh Portable 5120 (original) and have send the board to a technician who will recap the board. He sees resistor R21 looks bad too and measures an infinite value. He does not know what the value should be, can't read it anymore. 

Could someone have a look at R21 and tell us what the value of this resistor should be. Thanks a lot!!

ps. the picture is a clean board vs. our board

Screenshot 2020-07-17 at 16.27.59.png

f421ff09-ad76-4532-9ca1-6aa9327db967.JPG
Posted by: MindWalker on 2020-07-17 03:53:00
R21 should be a 100K

EDIT: here's the link, took some time to find it 🙂  --> https://github.com/nickpunt/nubus-se30/tree/master/Schematics/apple The screenshot is from sheet 14-19, bottom center.

PortableSchema.png
Posted by: gijsmans on 2020-07-17 04:16:06
R21 should be a 100K
Thanks so much!
Posted by: Stephen_Usher on 2020-07-17 21:30:34
From that image Q21 looks cooked. I had that on my machine when the +12V line got overloaded.
Posted by: gijsmans on 2020-07-18 17:41:39
R21 should be a 100K

EDIT: here's the link, took some time to find it 🙂  --> https://github.com/nickpunt/nubus-se30/tree/master/Schematics/apple The screenshot is from sheet 14-19, bottom center.
Schematics are superb.
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