Best options for long-lived ][+ and //e capacitor replacement

[Ralph]

I've got a small fleet of about 30 Apple //s (Six ][+ machines, another 20 //es, and 3-4 //gs
systems).

I'm wondering what the best approach is to keep them going another 30-50 years?

Some machines haven't been powered on since 2012, due to a couple of moves
in the 2011-2014 time period - so I've become worried about the effects on the capacitors.

At some point I realize that semiconductors will fail, too. I will deal with those situations
as they come up.

From reading blog posts and comp.sys.apple2 posts from Michael Mahon:

| I'd agree--the usual X2 type line bypass capacitor has an impregnant
| that is quite revolting!
| ....
| BTW, the supply will function perfectly without the line bypass capacitor,
| but it will put some switching harmonics back into the AC line (which
| could cause some interference) and it makes the supply a bit more vulnerable
| to fast overvoltage transients (so don't run the Apple on a line running
| an elevator motor ;-).
|
| I picked up several replacements on eBay for a few bucks, total.

I'm wondering two things:

1) Am I better off replacing alumnum electrolytics with "solid polymer" caps?
I'd expect a lifetime of 5000hours per cap, if I'm going to the trouble of replacing them.
200 hours usage per year x 25 years sounds about right.

http://electronics.stackexchange.com/questions/16898/do-solid-polymer-capacitors-really-have-a-longer-lifespan-than-electrolytic

2) It sounds like I want to pro-actively replace the RAFI "X2" bypass capacitors,
along with numerous electrolytics. But should I replace them in bulk, or wait until I see
a problem?

I worry that the biggest dange is a capacitor failure leaking bad goo on the power supply PCB or the motherboard. it's not the same problem as surface-mount caps leaking acetic acid on
an 68030 Mac or Amiga motherboard, but I really want to be able to use & demo
these systems periodically for at least another 25 years.

Are there high-quality capacitors with long-long component lifetimes to be had that would make
sense for this application?

[sicklittlemonkey]

On Sunday, 5 June 2016 07:15:36 UTC+12, Ralph wrote:
> 2) It sounds like I want to pro-actively replace the RAFI "X2" bypass capacitors,

Just FYI, I asked this question, and got an answer of sorts:
http://electronics.stackexchange.com/questions/174034/what-is-the-best-modern-replacement-type-for-a-metalized-paper-capacitor

Cheers,
Nick.

[Ianoid]

I'm not sure if authenticity matters once you go to replacing the caps with modern designs, but Ultimate Micro has recently announced a power supply substitute that fits in the Apple II/+/e/gs power supply case that I plan to use instead of replacing original caps that work (but may not in the future).

https://www.ultimateapple2.com/catalogzen154/index.php?main_page=index&cPath=1_16

It's not cheap, but seems like an reliable safe solution for keeping your Apple IIs going indefinitely. Then again, buying good quality caps in small quantities won't be terrifically cheap either.

ian

[Ralph Hyre]

Thanks for the suggestions.

It sounds like the polymer ones are the way to go. I'd be interested in seeing photos of the goo they release when they fail (thinking ahead to 2030, I suppose)

Since Apple supported component-level repair, I'm going to repair components for as long as I can. I imagine I will get to the point of having to replace entire supplies (I have three spares and a couple of bare PCBs for Apple //gs supplies, I believe).

[Michael J. Mahon]

The X2 line filter capacitor failures I've seen didn't "release goo", as a
faulty electrolytic might, but they crack and release an awful-smelling
vapor, with occasional signs of heat or even brief flame.

These capacitors are designed to "heal" in the event of an internal short
by melting away the metal nearest the short, and some of the dielectric.
The melting clears the short and life goes on--most of the time. When too
much melting occurs, the capacitor can overheat and crack its case or even
explode. The resulting vaporization of the dielectric impregnant is what
produces the awful, and persistent, odor.

After a catastrophic failure, the capacitor fails open, though the power
supply fuse is usually blown in the process.

Replacement of the fuse is, of course, required, and replacement of the X2
cap is also a good idea, though the supply will work fine without it.

The line capacitor is both a spike attenuator and an interference filter,
so it's worth having for protection, even though it's not necessary for the
power supply to function.

I don't recommend wholesale replacement of capacitors "just because". Most
capacitors will have very long lives, and replacing soldered-in components
always carries some risk.

Electrolytic capacitors are most likely to fail, usually by drying out,
resulting in increased Equivalent Series Resistance and/or decreased
capacitance. But even in the case of electrolytics, my motto is "if it
ain't broke, don't fix it".
--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com

[Michael Black]

On Tue, 7 Jun 2016, Ralph Hyre wrote:

> Thanks for the suggestions.
>
> It sounds like the polymer ones are the way to go. I'd be interested in
> seeing photos of the goo they release when they fail (thinking ahead to
> 2030, I suppose)
>
> Since Apple supported component-level repair, I'm going to repair
> components for as long as I can. I imagine I will get to the point of
> having to replace entire supplies (I have three spares and a couple of
> bare PCBs for Apple //gs supplies, I believe).
>

The real issue is size. There's nothing magic about the Apple II power
supplies, other than physically being long and thin. The voltages
are common, and it doesnt' need to supply a lot of current. There's that
famous mod of using an external IBM PC type power supply, it having to be
external since the power supply board isnt' long and thin.

But there probably are lots of options out there. There was a period when
I could get lots of switching supplies at the local surplus store,
probably lacking some voltages but small enough to fit into an Apple II
power supply case.

And nowadays, one can find all kinds of laptop power supplies that are
small, so those would fit into the II power supply case. Find one with
the right voltage, and then you'd need to add some regulators for the
lower voltages, as would be the case with a small switching supply that
didn't have the right voltages. The negative voltages would be missing,
but those are generally such low current that one could pull a small
transformer out of some old radio or something, and build a power supply
inside the II enclosure, along with a switching supply for the +12 and +5v
lines. I did this once for something else, the current draw was so low it
wasn't worth figuring out something better.

Michael

[Michael J. Mahon]

The drain on the -5v supply is only a few milliamperes, so a tiny DC-to-DC
converter that converts +5v to -5v is enough.

The -12v is used only for a couple of op amps, so it's a similar candidate.
Of course, RS-232 will also use +/-12v, but again only a few mA.

The only proviso is that there not be any peripheral cards that place
significant loads on the negative supplies, but that would be unusual.

[Don Bruder]

In article <QOOdnXu8Et3ykcrK...@giganews.com>,

As I recall (working from memory here, so might be wrong) the -12 supply
in a stock IIe is rated for a total draw of half an amp, and the -5 is
rated for 1/4 amp. I'm pretty sure the +5 and +12 are rated for 3 and 2
amps, respectively. It's just plain not a hefty supply. But then, it
doesn't really NEED to be. (For years, I'd shake my head in wonderment
every time I flipped through a magazine and saw the ads for PC supplies
that claimed to be able to handle a 200, 400, even 800 watt load - "Why
on earth would anyone need THAT much power for a computer???")

>
> The only proviso is that there not be any peripheral cards that place
> significant loads on the negative supplies, but that would be unusual.

Very. About the only cards that I can remember being particularly
power-hungry were sound cards. And those probably because they were
loaded with op-amps.

--
Brought to you by the letter Q and the number .357
Security provided by Horace S. & Dan W.

[mike.a....@gmail.com]

On Wednesday, June 8, 2016 at 1:19:11 AM UTC+10, Michael J. Mahon wrote:

<snip>

> The X2 line filter capacitor failures I've seen didn't "release goo", as a
> faulty electrolytic might, but they crack and release an awful-smelling
> vapor, with occasional signs of heat or even brief flame.
>

I've had two separate occasions that the X2 line filter caps have exploded, and in both cases they did release a orangey-brown foul smelling substance that required plenty of rubbing alcohol and cue-tips to get rid of. Even after removing the bulk of the "goo" from the PSU innards, some of the foul smell remained with the PSU case open. With the PSU case closed it wasn't very noticeable.

I'm in Australia and have 240V, so I don't know if that makes them more susceptible to exploding the "goo" around?

Cheers,
Mike

[Michael J. Mahon]

No, they sometimes explode on 115v, too. ;-)

[Michael Black]

But I wonder if the higher voltage makes the explosion more spectacular?

I've put tantalum capacitors in backwards, and those exploded real well.
And epoxy covered rectifiers explode well if you put them in backwards.
They used to have much larger bodies than the now common 1N400X series, so
there was more to explode.

I once had an IC explode, but I can't remember what I did wrong. It was
regular ttl logic, so I must have done something really wrong.

Michael

[mdj]

On Thursday, 9 June 2016 08:37:07 UTC+10, mike.a....@gmail.com wrote:

> I've had two separate occasions that the X2 line filter caps have exploded, and in both cases they did release a orangey-brown foul smelling substance that required plenty of rubbing alcohol and cue-tips to get rid of. Even after removing the bulk of the "goo" from the PSU innards, some of the foul smell remained with the PSU case open. With the PSU case closed it wasn't very noticeable.
>
> I'm in Australia and have 240V, so I don't know if that makes them more susceptible to exploding the "goo" around?

Yeah, I've had two that produced a spectacular amount of mess. Exploding X2's is now so commonplace that I assume a power supply will blow one if its condition is unknown, and I test all newly acquired Apple II's with one of the few supplies I've already fixed.

It's a sufficiently large effort to remove the supply board and the X2s that I just replace them as routine now - if it was easy to just cut the legs, I'd advocate everyone just do that on equipment they're storing/archiving instead of using. As it is, but the time I've dismantled the supply and removed the X2, fitting a new one is only another couple of minutes work.

[john]

1983 - electronics class lab, I built a variable voltage power supply, we
used to get caps and low value resistors and sacrifice them just for the
flames, smoke and other entertainment :)

I have 3 apple ]['s that I am going to fire up again after sitting in
storage for 15 years, any tips that may be able to prevent having
electronic failures such as caps blowing and fizzling motherboards?

[Michael J. Mahon]

There is a very good chance that your systems will power up in good
condition.

With devices using "linear" power supplies, like vacuum tube gear, the best
advice for powering them up after a long "rest" is to slowly increase the
AC voltage applied, taking an hour or more to reach normal line voltage.
The gradual increase in operating voltage allows possibly degraded
electrolytic capacitors to "re-form" their dielectric, reducing leakage and
potentially destructive heating.

But with the advent of switching power supplies, it is quite stressful to
apply AC voltage much less than the design voltage (because the switching
supply will make a "maximum effort" to provide it's rated regulated
voltages regardless of the applied voltage).

Some would recommend assuming the worst and replacing all (or most) of the
electrolytics before applying power.

I tend to assume the best in the absence of contrary evidence, so I would
"plug it in and turn it on". Experience indicates that this is quite
likely to work, at least as far as the power supply is concerned.

If a problem occurs, then it will need to be repaired (or replaced), but
that's not likely to be much more expensive or difficult than preemptively
replacing the electrolytics (though it may also involve replacing the
internal fuse and the bridge rectifier).

I expect you'll have good luck.

Give it a try and let us know!

[john]

I will do! but I have to get them all out of my storage locker, and that
may be a few weeks yet - I still have all the boxes of software and
manuals, but I know that a few of the manuals got damaged by some water -
but I still have lots of interesting things to learn about again! :)

[sicklittlemonkey]

On Thursday, 9 June 2016 10:37:07 UTC+12, mike.a....@gmail.com wrote:
> I've had two separate occasions that the X2 line filter caps have exploded, and in both cases they did release a orangey-brown foul smelling substance that required plenty of rubbing alcohol and cue-tips to get rid of.

Same here, but I found I needed a stronger solvent: water.

Water is much more effective at getting the goo off than alcohol.

Cheers,
Nick.