Macintosh plus anode cap => dead screen? — #21

Post #21 by didius

Source Forum	Macintosh plus anode cap => dead screen? — #21
Category	Hardware
Post Date	Sun, 15 Sep 2013 - 14:00
Original URL	https://68kmla.org/bb/threads/macintosh-plus-anode-cap-gt-dead-screen.28693/

Post

I took away about every part in the feedback control circuit, and tested them out.

Afbeelding_1.png.d38b931fe80171af8746a18d8e2848ff.png

However, my findings are different

Code:

Resistors:
R34: OKAY, reading of 1kOhm
R35: OKAY, reading of 1kOhm
R36: i have a reading of 12Ohm, schematics talk about 470? (resistor is also very different, more like disk shaped)
R37: instead of the 10kOhm i have a resistor of 390 Ohm +-5% (reading is ok)
R38: instead of the 1.2kOhm i have a resistor of 10k Ohm (reading is 9.8kOhm)
R56: on my mac plus this should be R59?

Capacitors
C27 and C28 have been replaced in the recapping proces
C21: instead of 0.1uF mine reads 103k =&gt; 0.01uF
(there is a 0.1uF in the area but that's C22

I've tested the zener, and there i get a reading of 0.62V (part number IN4001GI)