Apple IIe Manual Fault Dictionary

["anomaly3@mc.net" <anomaly3@mc.net>]

Apple //e Manual Fault Dictionary:

How to use this chart:

Switch on your Apple //e with no disk in any drives. Get out your logic 
probe, and test the pins on each chip and note their reading. Then check 
your list with the list below and compare them. Any inconsistencies 
could signal a faulty chip and should be tested and/or replaced.

       PIN #         1         2         3         4
CHIP        1234567890123456789012345678901234567890
----------------------------------------------------
LS125       PPPLPPLHPHPPLH

PLA         PPPPPPHPHLLPPPPPPPPH

FF          HHLPHPPLPPHPPPHH

Buffer      LPPPPPPPPLPPPPPPPPLH

LS245       LPPPPPPPPLPPPPPPPPPH

LS374       PPPPPPPPPLPPPPPPPPPH

LS244       LPPPPPPLPLPPPPLPLPLH

Vid ROM     PPPPPLPPLPPH

MMU         LPPPPPPPPPPPPPHHHPHPPLPPHPPPPPPPPPPPPPPP

Processor   LHPHOHPHPPPPPPPPPPPLLLLPPPPPPPPPPPOOPHPH

ShRegistr   PPPPPPPLHPPPPPPH

IOU         LLPPPHLLPLLHHPHOPPPPPPPPPPPHPPLLPPPPHPPP

LS10        PPPHHPLHLHHHPH

Dec/Demux   PPPPPPHLHHHHHHPH

All RAMs    HPPPPPPHPPPPPPPL

CD ROM      HPPPPPPPPPPPPLPPPPPLPPPPPHHL

S202        LHLPPLLPPPHPLH

EF ROM      HPPPPPPPPPPPPLPPPPPLPHPPPHHH

LS154       PHHHHHHHHHHLHHHHHPPPPPPH

Keybd ROM   LLLHLLHHPPPLPPPPHLLPHLHH
            --------             --

LS251       OLLHPOHLPPPHHHHH

RC741       PLLPPPHO

NE558       HOHHHHOHHOHLHHOH

Decoder     PPPLLLLHLLLHHHLLLLLLLLLLLLLHHHLPPPPPPPPP
                 --------- 

P = Pulse
H = High
L = Low
O = No Light

Pins 1-8 & 22 & 23 on the Keyboard ROM as well as pins 6-14 on the 
Decoder are readings made after "space bar" pressed.

+ These readings are taken under normal stand-by conditions.

That's all there is to it! Please do not ask what the chips themselves 
do - refer to the Apple //e Technical Reference Manual, in the Hardware 
Implementation section.

- Tony :-)

** This list was obtained from p.232 of "Troubleshooting and Repairing 
Personal Computers 2nd Edition" by Art Margolis published by 
Windcrest/McGraw Hill. ISBN 0-8306-2187-3. **

<<<<< DISCLAIMER: This post is for reference only - I will not be held 
responsible for any damages or personal injury as the result of the use, 
misuse, or otherwise of the information contained herein. The above 
procedures should only be performed by a qualified technician, or Apple 
authorized representative. >>>>>