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Apple III

Computers in Collection

General Info


TODO: 12V vs. 5V TODO: 12V RAM bizarre IC-on-dip packages TODO: System RAM diagnostic TODO: My RAM stack hack. Where’d those pictures I took go?!

Power Supply

C1: “250V~MP fo=3,0MHz”, “PME 271 M 622”, “Rifa GPF 40/085/56”, “0,22uF”: “Metallized paper cap 0.22uF 250VAC 068-22400010”. According to Digi-Key/datasheet: 20.3mm lead spacing, 24mm x 16.5mm x 11.3mm. Holes on PCB are 15mm or 20mm spacing. suggests Kemet PHE840M family is a substitution for PME271M. Try Kemet ‎PHE840MB6220KB12R17‎ or ‎PHE840MD6220KD13R06L2‎.

Parts values and characteristics were also checked against “Astec_Power_Supplies_Aug82.pdf”

Apple III, serial A3S1-021975



Attribute Value
Manufacturer Apple
Model A3S1
Serial A3S1-021975
Source 2019/Aug/17, craig@OMSI

Logic Board

Apple III logic board, partial, perspective 1

Apple III logic board, partial, perspective 2

Attribute Value
Manufacturer Apple
Part 820-0043-00
Serial TODO:
Markings “APPLE COMPUTER” “820-0043-00”
Source 2019/Aug/17, craig@OMSI

RAM Board

Apple III main memory card, 12V RAM

Attribute Value
Manufacturer Apple
Part 820-0021-01
Serial TODO:
Markings “APPLE III MAIN MEMORY CARD” “APPLE 1980 820-0021-01” “610-_-” “MADE IN U.S.A.”
RAM Voltages includes 12V
ICs 16 x Mostek MK4332D-3, 32 x TMS4116-20NL (“8118” “8122”), 1 x ITT 4116 3N “8128”
IC sockets all RAM chips
Source 2019/Aug/17, craig@OMSI

RAM rows B and C are 18-pin sockets, which presumably accept 32Kbit chips (like the Mostek MK4332 module-ICs) and 16bit chips if placed so that socket pins 9 and 10 are open.

Power Supply

Attribute Value
Manufacturer Astec
Model AA11190
Serial 19007983 (hand-written)
Date Code “8035”
Markings “02015203” “Made in Hong Kong”
Source 2019/Aug/17, craig@OMSI

External Floppy Drive

Attribute Value
Manufacturer Apple
Model A3M0004
Serial A3M0004-00492
Source 2019/Aug/17, craig@OMSI

CRT Monitor

Apple III - Apple Monitor III

Attribute Value
Name Apple Monitor III
Brand Apple
Model A3M0039
Serial B2K 158852
Manufacture Date November 1982
Manufactured In Japan
Manufactured By Hitachi
Source 2019/Dec/21, Hayden@Craigslist

Maintenance Log

+5V supply voltage is reasonably correct and safe.

No video output and no floppy-busy LED, but motherboard LED lights.

Apple III bad video output


Rifa capacitor (C1?) popped. TODO: Replaced? With which part number?


(TODO: Is this logic IC testing?)

Tested OK: B[10,12,13], D[2,3,4,5,6,7,8,9,11,12,13], E[2,3,7,8,9,10,12,13], F[2,3,10,11,12,13], G[2,3,6,7,10,11,12], H[7,8,9,10,11,12], J[4,6,7,8,9,10,11,12], K[3,7,8,9,12] Untested: B[1,4,6,7,9,11], C[2,9], D[10], E[4,5,11], F[5,7,9], G[4,9], H[3,4,6,13], J[2,3], K[1,10,11]

TODO: Document the RAM repair!

Apple III RAM diagnostics results 1

Apple III RAM diagnostics results 2

Finally back to working! This is an Apple demo for the Apple III’s high-resolution graphics.

Apple III running a pie chart demo


TODO: List documentation? Or is that far too fiddly?