After last month’s post about A2S1-5025, I received several requests for photos of specific areas of the machine that were not visible in the first set of pictures. Here you go:
This is the keyboard, removed from the case.
Bottom of the keyboard.
Apple part number 01-0425-01 is described in the Apple II/II-Plus Level II Service Manual (1981, Pre-Release Version, available in PDF format here – do a text search for “keyboard varieties” in the file) as “The first Apple keyboard,” but it is not. The early revision 0’s shipped with 01-0341-01, an example of which can be viewed here.
As with the Apple II board itself, the early days of production saw the keyboard undergo a number of changes more evolutionary than revolutionary. The circuit board was made shorter and wider to better fit the case, with the silver leaf plates formerly used to secure the keyboard to the plastic sacrificed to make room for the reconfigured electronics. The silk-screened Apple part number was moved from the lower right to left…
The encoder chip and associated electronics were migrated to the lower right…
These long, threaded, brass posts lined up with the spacers on the PCB to provide a mounting system.
The mounting set up is reinforced with these hollow spacers that also align the keyboard assembly on the brass posts.
Here’s the upper shell, removed from the base pan and keyboard.
Close up of the black nylon “velcro” lid fastener pad.
When trying to determine whether an Apple II is a revision 0 or some later production model, there are a few identifying markers on the motherboard that can quickly be verified. One of the indicators easiest to identify is the presence (or lack) of the color killer circuit, which includes a transistor visible on the PCB in the area to the right of the CPU, between rows F and H (there’s no row G), like so:
This circuit was added to production beginning with the revision 1 boards so it’s simple math: no transistor means the board is a revision 0.
Another “dead giveaway” that you’re looking at revision 0 board can be found under the 6502 chip. Or rather, not found. All Apple II boards beginning with the revision 1 run were assigned a part number which, early on, could be found by taking a peek under the processor. As an example, here’s what you see when you pry up the CPU on a rev 0 board, with the revision 4 Apple II Plus below it.
These memory select jumper blocks allowed users to upgrade their memory easily. Simply plug-in your new DRAMs and insert the appropriate jumper blocks to let the computer know how much memory it had to work with. The presence of these, while an indicator that you are looking at an early Apple II board, doesn’t guarantee a revision 0. Later boards shipped with them soldered in place and at some point they were removed altogether.
This is one that often gets missed in auction photos on eBay because of the awkward position you have to hold your phone in to get a clear shot, but a surefire indicator is the copyright date that appears just above the system ROMs and below the Apple Computer logo. Only revision 0’s are marked ‘1977’; every thing after that stamped with a 1978 copyright (or later.)
Someone asked for a shot of the underside of the 6502, so here you go. I assume “PHIL.” means it was manufactured in the Philippines. No idea what the other text might mean.
I’ve got a few more areas to cover, but that’s probably enough for now. I’ll knock the rest out in a third post next week.