Apple //e ASTEC AA11042C PSU Circuit Diagram

I’m starting the decade off with the circuit diagram for the ASTEC AA11042C which is from my original 1984 enhanced Apple //e. Possibly the Rolls Royce of the models due to it’s large size and design refinements.

by Mark Cummings

When I started this project I thought it would be very quick as the PCB looks very similar to the AA11040C/B which I recently completed. A bit of cut and paste and I’d have 3/4 done in no time. And while it IS very similar there were enough differences to create more work than I had anticipated. Firstly the PCB is longer and wider than the earlier models and almost all the components have moved a little to cram in the extra parts on the primary end of the circuit board, that being the IEC power entry socket, a choke, the main X2 filter cap and bleeder resistor which were previously mounted in mid-air or on the back of the IEC socket.

240V ASTEC Power Supply case with it’s unique black Apple labelling

I did a little online research and found a few other images of a european 240V version but I was unable to collate enough information for the 115V version which I’m sure exists since there is a jumper J2 marked on the PCB but not installed in the 240V version. The jumper connects in the same way in the circuit as it does in the AA11040C/B. If I find more information on that version I will update this page later.

The inductors amidst the secondary capacitors looked a bit smaller, so I whipped a couple out and tested them in a tank circuit as I did previously to determine their approximate values.

The secondary electrolytic capacitors have been consolidated into a lesser number of types and sizes, probably to simplify manufacture and save costs. A lot of the secondary capacitors now have a higher voltage rating of 16V which may account for a longer life.

Circuit Diagram created with Protel Schematic application

PCB composite overlay generated from Protel PCB Application

Black and White overlay without the underlying track work

The Parts List with additional information.

Safety precautions must be taken into account if you are working on these power supplies as I have mentioned previously. After unplugging the power cord wait at least 10 seconds for the main filter caps discharge before touching anything inside.

If anyone wants to contribute information on the 115V version of this power supply, please contact me by email (included in the circuit diagrams). Pictures or component values is predominantly what I am after.

Also if you find any errors or variations within your supply let me know.

While I had this supply apart I took the opportunity to check all the electrolytic capacitors. I had previously replace both mains X2 filter caps C1 and C23. If I recall correctly the original RIFA branded cap C23 did smoke in this supply and I replaced it some time ago along with C1. Surprisingly all the electrolytic caps on the primary and secondary side were all original, around 36 years old and the power supply is still working.

Just to be safe I checked ESR values on all electrolytic caps and the only one which required replacement was C7, a 220uF 10V electrolytic, a common failure point I’ve run into before on other Apple II power supplies. The ESR measured 0.83 Ohms (almost three times higher than acceptable) and it’s capacitance measured 250uF which goes to prove that capacitance is not always a good measure of capacitor health.

I’m not sure why this one seems to fail more often, but I suspect it may be because in-circuit it is not always biased in the correct polarity with a small DC reverse voltage across it. I wonder if it should be a bi-polar electrolytic capacitor, but thats for a future investigation.

Top view of the PCB after removing the top of the enclosure

A big shout out and thanks to Dean Claxton once again for some close up images and component information that helped me with some of the part variants.

Apple have incorporated an unusual black branding onto the power entry panel and the ASTEC’s labelling is now on the other end of the case.

Update: Rosario Vambaca pointed out that the Enclosure also came out in a silver version without the blackened power entry panel.