Apple II Europlus Power Supply Failure (ASTEC AA11042C)

[ben7]

Re: Apple II Europlus Power Supply Failure (ASTEC AA11042C)

Yes, it is a good idea to replace the electrolytic capacitors in the power supply. Ones that old tend to explode when they fail, with a very loud bang - and shredded paper goes everywhere inside xD

[PeteS in CA]

Re: Apple II Europlus Power Supply Failure (ASTEC AA11042C)

When I saw that Hitachi 2SC1942 switching transistor, I thought, "I bet that's a TV horizontal output transistor." I found a datasheet, and sure enough ... . Astec, in those days at least, was very good at selecting inexpensive parts without hurting performance. This P/S probably operates around 25KHz, not that much higher than the 15.75KHz frequency of an NTSC (i.e. US) TV. And Hitachi probably made those transistors by the millions ... nice low cost.

If a lytic explodes or spews its guts, you have to clean off the splattered electrolyte really well. That stuff is very conductive! In an electrolytic capacitor, the electrolyte is part of the current path, not the dielectric - the more conductive the electrolyte, the lower the ESR.

[cheapie]

Re: Apple II Europlus Power Supply Failure (ASTEC AA11042C)

15.75KHz frequency of an NTSC (i.e. US) TV.

Is that what makes them squeal?

[ben7]

Re: Apple II Europlus Power Supply Failure (ASTEC AA11042C)

Is that what makes them squeal?

Yeah I think so.

Ugh, that squeal drives me nuts sometimes xD

[PeteS in CA]

Re: Apple II Europlus Power Supply Failure (ASTEC AA11042C)

Yeppers. Europe has a different format, and I think Japan may also. Not sure what the horizontal frequency is in those formats. The vertical frequency for NTSC is 60Hz, interlaced, for a net frame rate of 30 per second.

For the terminally curious, I should note that those frequencies are slightly rounded. Those were the original frequencies, but were changed very slightly with the introduction of color TV. The changes were necessary, but so slight that existing B & W TVs still worked. This was all before I was born, but I read about it back in the early 70s.

[Chevy2]

Re: Apple II Europlus Power Supply Failure (ASTEC AA11042C)

The same thing just happened to me. In looking for a replacement from mouser for my exploded .1uf RIFA, the replacement looks almost exactly the same. Can someone help me find an equivalent replacement that this wont happen to again?

[stj]

Re: Apple II Europlus Power Supply Failure (ASTEC AA11042C)

got a foto of it?

the problem isnt the cap really,
it's just that the epoxy casing shrinks and cracks after about 20years and lets moisture into the guts.

if your replacement is new, and not made decades back then it will be fine.

[Chevy2]

Re: Apple II Europlus Power Supply Failure (ASTEC AA11042C)

got a foto of it?

the problem isnt the cap really,
it's just that the epoxy casing shrinks and cracks after about 20years and lets moisture into the guts.

if your replacement is new, and not made decades back then it will be fine.

Its the exact same as the .1uF pic at the top of this post. They must have just added the larger cap for Europe.

[japlytic]

Re: Apple II Europlus Power Supply Failure (ASTEC AA11042C)

Yes, it is a good idea to replace the electrolytic capacitors in the power supply. Ones that old tend to explode when they fail, with a very loud bang - and shredded paper goes everywhere inside xD

This is referring to the electrolytics which do not have vents.

[stj]

Re: Apple II Europlus Power Supply Failure (ASTEC AA11042C)

Its the exact same as the .1uF pic at the top of this post. They must have just added the larger cap for Europe.

but is it very yellowed or cracked?

[PeteS in CA]

Re: Apple II Europlus Power Supply Failure (ASTEC AA11042C)

The same thing just happened to me. In looking for a replacement from mouser for my exploded .1uf RIFA, the replacement looks almost exactly the same. Can someone help me find an equivalent replacement that this wont happen to again?

C2, if you're dealing with an Apple 2 P/S, the thing is 20-30 years old (maybe over 30). Things made by humans have finite lifetimes, and 30 years for electronic parts is pretty good. The Rifa PME271 series has been around a very long time (since the late 1970s that I know of). It's as good as any competitor's parts. If it hasn't been mentioned already, a principal failure cause for these parts is voltage surges from the power line, so the cause of your failure may have been the utility power at your home, not some internal failure mechanism. If you're in an area that gets lots of thunderstorms, that's not a good thing. If you use power strips with surge protection, I recommend replacing them ever couple of years.

[kc8adu]

Re: Apple II Europlus Power Supply Failure (ASTEC AA11042C)

i suspect that case cracks letting moisture in is what kills these most often.
i rebuilt 2 of these units and the caps blew up in one after 15 minutes of running.
these had not been run in 10 years.
the caps went bad and they were given up as dead.
new caps there too and these are ready for another 20+years of use!
these were used in an rf tag system to run the deactivate amp.
they run an hf rig nicely.

[PeteS in CA]

Re: Apple II Europlus Power Supply Failure (ASTEC AA11042C)

I think I saw a 1986 date code on the 14-pin IC, and it looks like it might be a discontinuous flyback. Maybe a single O/P, 120W-150W? Power One made good stuff.

[kc8adu]

Re: Apple II Europlus Power Supply Failure (ASTEC AA11042C)

those datecodes are about right.
a friend got these during the cb craze and the deact amps(motorola eb63 reference design)
these power supplies took some incredable pounding running these amplifiers.
they died from output lytics leaking.
you can see what i used.
an amp and one of these rebuilt supplies is running behind my yaesu ft-817.

[iMic]

Re: Apple II Europlus Power Supply Failure (ASTEC AA11042C)

I decided to perform a more extensive overhaul of the PSU and Floppy Drive recently. I had a small mishap that involved connecting the floppy drive to the Disk II controller card one row of pins over. Toasted the drive, and the PSU hadn't sounded right ever since. It was hissing while running, and the noise would become louder with additional load.


The toasted component inside the drive was the 74LS125 Bus Buffer IC, apparently a common failure when mis-connecting the drive like this.



I replaced it with a Texas Instruments SN74LS125AN from Element14, and the drive now works again. I'm fortunate in this case, because sometimes the MC3470P amplifier IC can also burn out when this happens, but mine survived.


As we know, the capacitors inside this power supply have always been suspect throughout the entire time I've owned it, and I figured that 33 years was enough. I replaced every capacitor inside the supply with new Panasonics and Rubycons (with a 105C maximum operating temperature).




Sure enough, it doesn't hiss anymore, and it can sustain whatever load on the power supply the Apple II throws at it.




I still haven't replaced the bulb for the power lamp on the keyboard though. I'm not even sure what type it is, but I've been told it isn't that easy to track down. Chances are I'll have to open it up and take a look at some point.


Cheers,

~ iMic.

[NickNZ]

Re: Apple II Europlus Power Supply Failure (ASTEC AA11042C)

Hi iMic.

First poster here - in NZ. I've just replaced my RIFAs with Suntans too ... and I might also do the AC side high voltage dielectrics. Any comments on those parts? I'll probably just check Jaycar.

BTW, you've probably already found out, but just in case, the mod you mention:
"Interestingly, it also looks like the machine has been modified. One chip has been removed, a chip socket has been stacked on top of the existing chip socket, but with two red and black wires coming off it. Then the existing chip has been stacked on top in a piggyback configuration. The two wires travel up to the keyboard connector, with the black connecting to the second pin from the left, and the red connecting to the third pin from the right"

... will probably be the Shift Key Mod. This ties the Shift key to paddle button 2 so that old Word Processing software can use that for entering upper and lower case. See James Sather's Understanding the Apple II, page 7-36.

Cheers,
Nick.

[stj]

Re: Apple II Europlus Power Supply Failure (ASTEC AA11042C)

suntan is junk,
new RIFA's or WIMA's would have been better.
that said, they will still last many years.

electrolytics, dont overdo it with ultra-low esr stuff, i would use rubycon YXF or YXG.