Mac 128k ~ Plus Analog Board Analysis

[H3NRY]

Gaaahhh! Part numbers! In any big company everything has a part number, and that number may be on the part someplace. There is a number for the board artwork, that is the layout of the traces. There is a number for the silk screen legends. There is a number for the bare board. There is a number for the board stuffed with components. There is a functional number, ie power / sweep for 128K, different from power / sweep for Plus. There is usually a bar code to identify the part for warehousing, and of course a part number for the bar code label itself, which may also be on the label. Every one of these items requires a complete spec sheet, which is why engineers go crazy trying to crank out all the paper work. Each spec sheet has its own part number, too!

So every time somebody changes a capacitor spec, the assembled board spec has to be rev'd, the bill of materials for every higher assembly in which the board is used has to be rev'd, the spec sheets for the bar code labels have to be rev'd... it's a wonder anything at all gets done. At I*M it took 3 days to revise the spec sheet for a bar code sticker because the format of a specification was so complex and precise (and undocumented). All to change one part on an assembly and bump it from rev c to rev d.

As a result, there's great pressure to use parts already in the company's system. There may be a new better part available, but you know it'll take you two weeks of paperwork to request the part, and it'll take purchasing 3 months to qualify and approve the part. Not that they do any actual tests mind you, they request statistical failure data, reliability guestimates, costs, production levels, production ramp rates, etc. etc. And if a competitor takes a purchasing manager out to a very nice lunch, you may be asked to redo everything for the competing part. xx(

 

[Mac128]

H3NRY, thank you for the delightful insight to the process. That certainly explains a lot. Especially why it may have theoretically taken Apple so long to revise the under-powered components on analogue board, cost aside. I never stopped to consider the bureaucracy behind part numbers.

 

[H3NRY]

Apple occasionally thinks different. The design of the Apple 1 and II, and the Mac were done in the absence of a bureaucracy. (See Andy Hertzfeld's wonderful stories at http://folklore.org/index.py). As a result of designing under the pirate flag, when the Apple II and the Mac first shipped, Apple did not have schematics or documentation. The recent auction of the Apple II rev 1 to rev 2 motherboard documented the company's effort to trace an accurate schematic for the Apple II. There was a "schematic" of the Mac 128 which Burrell did which consisted of separate drawings of each chip and the signal names which appeared on each pin, but it was rather like having a photo of every bolt and piston ring and gasket of a car, without a picture of how they fit together. As a result, for several years after 1984, Apple's engineers had the Beck-Tech schematics in their cubicles, because there was no Apple equivalent.

Also as Andy's Folklore tells, the Mac team broke up after the Fat Mac design, everyone moving on to new projects inside and outside the company, so the Mac was hanging in limbo for a while as "the Navy" picked up the pieces where "the Pirates" left off. This sort of story makes Apple such a fascinating study. Since the return of Steve, Apple has learned to keep a team together beyond rev 1.0, listen to customer reaction, and get 2nd and 3rd generation products out that are ever more irresistible.

 

[NOBRU]

Hello everybody

I'm new in this forum ; I own an original Mac 128 (week 24 of 1984) ; it was incidently found aside a dustbin 15 years ago ; althougt the case has yellowed a bit, the inside looks pretty.

It seems that the analog board is failing, because strictly nothing happens at power on. Having a background in electronics, I have checked the PCB ; the fuze is OK, the power switch as well. As far as I could check without unsoldering components, no obvious failure can be detected. No component gives evidence of ageing. I have searched the on the net : no schematics of analog board available. Where do you think I could find one ? It is likely that an amateur has re drawn it, if original does not exist...

Moreover, reparing that kind of switching power is tricky ; has anybody got an experience in that way ?

My PCB is an international one (630-0108) ; thanks to the pictures posted hereover, I have verified that even if the general layout is similar, component numbering is not the same as for (630-0102) : for example R9 and R16 become R12 and R19 in 0108.

Thanks for your help

 

[NOBRU]

Hello

I've found the schematics in : http://dyne.org/museum/apple/stuff/mac/andreas.kann/; this is the first step (110V version, not international).

Now I have to use it ....