I'm starting this new section to share my experiences selling, repairing, and designing electronic devices from the early 1970's forward. I was a field sales engineer for some early electronic companies including CTS Microelectronics based in West Lafayette, IN, Magic Dot, in the Minneapolis, MN area, Signetics of Sunnyvale, CA, Monolythic Memories, Rockwell represented by the John G. Twist Co, and EXCERT, INC, a mail order computer company I started and folded after joining Intel for a brief time in the early 1980's. Most of my initial attempts will be to place online some information about the Rockwell AIM-65 that might be in sparse supply. I am willing to act as a broker for people wishing to sell or acquire 6502 apparatus.
After searching the web for specific threads about the AIM-65, I noticed that some people are attempting to resurrect these early development systems. I functioned as a distributor, repair and parts center and system integrator for many years while these were in production and therefore have retained some knowledge, documentation, development boards from the varied vendors, and some spare parts. I am willing to try to respond to any questions one might have regarding these items.
An initial topic that I picked up from the Dead AIM 65?? thread was that these boards were known for their inability to start up reliably. I only noticed that specific problem on a batch of boards that came through my business in about the middle of the production run. I found that the CPU oscillator wouldn't start up reliably unless it was slightly off-balanced in one direction. If I remember correctly, the Rockwell engineers designed this circuit using 7404 invertors with 1.8k resistors to both sides of the crystal which was probably okay normally because the tolerance of the values usually meant one side was off value by 10% or more from the other. But possibly they ran into a batch of resistors that was in very close tolerance to the others and those oscillators would not start up reliably as they went into a sort of quasi linear modes requiring several resets to get going. I think I soldered a low value cap (10pf?) across R3 (3.3- a pull down resistor) or one of the 1.8k resistors to provide the necessary unbalance upon start up. I'll try to dig back into my notes and find out exactly how I accomplished this.
Some have complained about the 2114 RAM chips going dead even while sitting on the boards in storage. I have not run through my stash of chips and tested them so I'm curious to see if I have the same conclusion. I have chips from several manufacturers so it might be localized to just a vendor problem. I have noted that some of my sample chips that were protected with black static foam rubber have had their leads rot off while sitting around in my basement over the years. These were normally the chips with gold plated kovar leads on ceramic packages. Again I haven't tested these to see if they still function. I will have to mount them onto a socket and carefully solder the remaining stub to the socket pin to be able to test them!
I have many samples of MMI PROMS, Signetics & Intel chips, and CTS hybrids, Plus I have an assortment of Rockwell chips including parts from the PPS 4 and PPS 8 families including a Universal Assemulator & TTY using an RS 232 current loop and paper / Mylar tapes.
Some have complained about the lack of application notes AN's surrounding these families. I will try to scan and post them as time permits or by necessity in answering inquiries! Should I use the PDF format or just DOC files?
David E. Colglazier (DaveC)
Another subject that I read about shared tecniques
for trouble shooting the AIM-65. An oscilloscope surely helps in
determining if the crystal is doing its job by feeding the CPU and I'd
encourage anyone to learn how to use one. It is only necessary to
have the CPU, the lower RAM Chips (Z2,3), the monitor ROM
set, for the machine to come alive...you won't know it but it will
still be looking for its peripherals that are coded into ROM. At
this point the 555 timer reset can be checked with a VOM or
O-scope. Once you're sure that the reset line is not stuck, you
can go on to the
crystal circuit. I pull all the other socketed devices from the
board at this point to get through these checks. Once you're sure
you've got a live system, you can start adding back in the I/O devices
to get the bad device located. The display would be a good start
and then the keyboard so you have some interaction with the
system. Most of the time we assume an electrical component
failure but more often than not, I also found mechanical/electrical
failures at the interfaces. One particularly hard troubleshooting
job was an RAM error intermittently! I would check out all the
chips in different sockets and they'd all work just fine except when
inserted into one address space. All the socket pins looked fine
but on careful inspection of the solder side, I noted one pin not
protruding above the bubble of solder. This pin had bent back on
the underside and while making contact, it was not firmly attached to
the solder or had come loose from the twisting of the board or the
insertion of the RAM chips. I repaired that socket and everything
worked fine from then on. Physical inspection of all
electrical/mechanical interface can reveal the oddest problems.
No doubt, components go bad, but sometimes it can be just that a simple
resoldering will fix the problem.
I've added some comments to the section above and
will now go on to a new tool I've been using since I returned to PC
repairs. A Techie friend, Jim Justin, turned me on to a quick way
to remove RAM chips that are soldered directly to a through hole PC
board. What he said to do was to get a heat gun and if not trying
to save the board, just heat up the solder side and insert a small
screwdriver or similar tool under the chip and just pry it off.
Most chips have just a few pins bent to retain them while going through
the solder wave machine and this worked just fine as long as I didn't
want to save the PC board. I've refined that method since and am
able to do surface mount chip removal and replacement by adjusting the
heat carefully to prevent trace lifting. I've used it to replace
486 CPU's and smaller devices. I even repaired a Pentium level
CPU area when I discovered one of the inductor chips had been sheared
off during handling or shipping. I never found the component but
salvaged one from a power supply area on a defective PC board.
The old solder sucker still has it's place for me but when I need to
heat up a whole chip for replacement, I normally use this new
method. Careful regulation of the distance of the heat gun from
the board is the critical technique. I also acquired a heat
shrink gun with a focusing tip and found it to be sufficiently hot
enough to do very precise component repair work without disturbing many
Another tip Jim shared with me concerned multi
layer PC board troubleshooting to find hidden defective traces.
This one works but is very hard to do unless one has access to a known
good board. If you know you have a broken or intermittent
internal trace, you need to locate it and reroute the conductor
externally assuming this is not an overly critical high speed date line
and can tolerate another and possibly longer or shorter route.
With no power applied to either PC board, you take a pad of steel wool
and connect it to a VOM, hopefully one with a audible signal indicating
continuity. Then by dabbing the pad to the boards alternately,
and changing the other lead to single traces, you can locate a general
area where the broken trace is located. Hopefully you won't find
more than one but this can be used successively even in that event to
find additional broken traces since you have a known good board.
Once the general area is located, you can lose the steel wool pad and
revert to point by point continuity checks. It is time consuming
but it does work!
I have been corresponding with a fellow AIM user
and he had never heard of the Seawell group up in Seattle in the late
1970's so I put up a couple of scans of their offering on this site at
One of their more humerous product titles was
their Little Buffered Motherboard. It is a great product and I
still have two of them for using their Prommer II and their RAM/ROM
expansion. Unfortunately, I didn't retain their disk system as it
was quite a luxury to have one of those back then!
You will also find a narrative about the various
AIM-65 schematics and what revisions were made to the PC main board at
I will try and scan the large schematics and post
them when I find out how to do it and also the time! I finally
found my Commodore C64 1541 disk drive interface card for the AIM with
schematic, manual, and software in PROM. I had tucked it away
along with some Auto Vector keyboard cards, a Micro Interface tape
card, and some Cubit interface cards and PROM programmer. I also
plan on putting up a small area to sell and exchange AIM 65 surplus