I'm preparing my Apple II Rev 0 and related documentation for sale soon, as mentioned in a earlier post on this forum. I last powered it on successfully in September 2014 and let it run a few days, with on/off cycling every so often. Turned it off, backed away in its Apple carrying case and put it on a shelf.
I'm the original owner, purchased it in late 1978 all with its original PSU and chips, Serial # A2S1-3465, PSU A2M001-3615 (toggle switch), and used it extensively for generating vector graphics used in professional laser shows. I graduated to the IIe around 83-84. It has been periodically turned on (booted) to maintain its health. I have to admit that I was surprised that it powered up to all the correct Hex mode, FP Basic prompts in 2014 since it was last turned on and exercised about 8 years earlier.
I've been taking photographs of it and its accessories for the Ebay posting. When it came time to take current photos of operational display screens...it would not turn on. The PSU was totally dead. I had purchased a full set of replacement caps for this eventuality a few years ago and intend to repair the PSU. In the meantime I'll use a spare IIe PSU to make sure the MB is still viable. It has the FP ROM card all the original cassette tapes and more.
I've read many Rev 0 and PSU post on this forum over the years and noticed a lot a questions about whether there were Rev 0 PSU schematics and component lists, etc. The Rev 0 PSU schematic in the Apple II Reference Manual appears to represent one of the earliest incarnations and is not accurate for my Apple II and PSU serial numbers. The bottom of the PSU PCB is "PWR SUP 4A", so it is probably a 4th generation to what is shown in the Reference Manual.
So I've taken extensive photographs of my PSU and its components, including the single sided PCB and created a component list.
Thought I would first see whether there is any interest in my posting furthing information before continuing (because maybe its already on the forum and I've just not seen it).
Cheers,
Just post what you have. It doesn't matter if there is interest right now or not. Someone will definitely find your work useful in the next 100 years.
Thanks CVT, will do so.
I did just find this post from 2018 of an almost identical PSU, https://www.applefritter.com/content/help-recognizing-early-apple-ii-psu. The serial number is much later than mine but the PCB traces are identical. The key differences are shown by these photos, first mine, then his.
20230419_213303-cs.jpg
Drakepirate's PCB below:
IMG_9255ss.jpg
I just found the key difference between these two early PSU PCBs is found in the very lower right-hand corner of the boards. There is a trace widening and rerouting in the later version in the 10 o'clock position of the "ETCO" lable, AND the addition of what appears to be a 39 Ohm resistor just above the Apple logo on the later version. Its hard to know if this 39 Ohm resistor is original.
It is not "ETCO" but rather "FETCO", a circuit board assembly service company, and may still be in business https://www.fetco.com/parts-warranty, or maybe it is a derivative from the Apple era FETCO.
C1 and C2 measure good with the Altas ESR70
The 470uF/6.3v radial electolytic was questionable, noticable bugle on the "can's" top surface, Atlas ESR70 measured 1027uF ESR=1.22
Of the three axial 10uF/15v electrolytics, C6, C7 and C22, one was "open" the other two very high ESR > 40 but measured 10uF.
Progress being made on component list and their layout location on PCB that conforms to the labeled schematic found in the Apple II Reference Manual circa 1977/78 shown here:
A2PowerSupply-2-c.jpg
After electrolytic replacement
I tried reforming some of the caps but in the end decided it made more sense to put new , low ESR ones in. Most I got from Mouser.com, one came from Newark because Mouser only sold in quantities of 200 (but at 80 cents apiece).
Most all of my A2M001-3615 PSU schematic components, shown above, have their values or part numbers associated to their Identifiers (Rx, Cx, Qx, CRx, etc.) and I will post the list soon. There were only a few glass diodes I did not confirm but could be 1N914 or 1N4148 or similar. I chose not to desolder them in order to see if a part number was on their underside.
Original
A2M001-3615 Original
Does anyone have some idea how that SMPS works? Four transistors. It is the ultimate in simplicity!
It looks like Q3 is the main driver transistor switching the supply, and the top winding on the left side the main driver from the mains power.
R4/C4 looks like a snubber to protect Q3 from voltage spikes.
The base of Q3 is connected to the bottom coil on the left side, which looks like the primary feedback winding.
It looks like Q1 shuts off Q3 through Cr7. Q2 I think is there to limit the current through Q1, because as the current in Q1 increases, the voltage across R10 increases. As it approaches 0.7 V, Q2 turns on and raises the voltage of the emitter of Q1, lowering the emitter-base voltage of Q1 and thus limiting the current through it.
AR1 I think is to limit the time Q1 shuts off, because once AR1 is on, the capacitor C8 discharges and eventually the current through the base of AR1 drops to zero and AR1 shuts off. It could be that the AR1 transistor is there to ensure there Q1 does not prevent startup?
CR5 looks like its a zener diode that provides the regulation by conducting to the positive supply when the voltage reaches a certain level, turning on Q1 and shutting off Q3.
It looks like CR11 turns on when the voltage in the winding its connected to (third from the top on the left) is a high enough voltage so that CR11 starts to conduct and draws current away from the emitter or Q1 enabling it to turn on and shut off Q3, which is another feedback winding.
C6 looks like it there to provide the voltage to turn on AR1 and the diode CR9 prevent C6 from having a reverse voltage.
Anyways that must have been fun to design in the mid 1970s. There were probably some transistors burned creating that.