An Idea, header + epoxy = easily replaceable cap

[uniserver]

Is there any merit in this idea what so ever?

I'v not tried this, but i am curious if it would work, as long as the epoxy was thick enough, I feel it would create a reasonable mechanical base.

Also, I think the radial cap would be trimmed installed and then laid over on its side.

I was thinking maybe the header would be soldered with the leads bent, one forward and one backward.

Just throwing around ideas.

 

[olePigeon]

Wouldn't it be easier to just use tantalum capacitors instead of replacing the old cans which risk leaking onto the motherboard?

 

[uniserver]

tants are not the go to end all... they do go bad you know...

Caps are a wear item, I would like to come up with a solution that would make the caps easily replaceable...

or easily removable for long term storage,

Yes, tants don't leak, but they can catch fire.

and the new polymer solid caps, they are nice, but again still have a life, and still will go bad, and will have to be de-soldered at one point,

every time you mess with those pads you are taken risk.

So my idea is to make a solution that that allows a user option to replace/remove these things.

that way you will never worry about damage to the PCB, till the end of time.

 

[James1095]

That's a lot of work and additional potential failure points to avoid a bit of soldering every 20-30 years. Modern capacitors are better than the old ones ever were, and while tantalum capacitors *can* fail, as can chips and transistors and anything else, but they're certainly not a wear item. I have lots of old stuff with 30+ year old tantalum caps that still work fine.

 

[uniserver]

IC's are not designed to be a wear item, Capacitors do end up being a wear item, they WILL all go bad, just like the seals in all hydraulic cylinders. I guess my argument is what about 40 years from now or 80 years? All though thermal expansion and contraction can cause anything issues over time... I mean look at the issues with the Apple III, not really issues with the IC's but more with the socketed type connection. humm.

Don't think I would have to worry about issues with expansion and contraction with the caps, also a header would be just as reliable as any of the other headers on many points / and various computer pcb's, non soldered connections including power, floppy, scsi, sound (not including the IIsi's sound connection flaw)

Just like during the last 100 years they would have never known that all this polluting and gross over population would cause 129 degree days in places like Australia. Or else maybe if they knew they were causing some massive global warming, the powers to be might have enacted some stricter policies sooner.

 

[James1095]

If you're worried about tantalum capacitors failing, there are multilayer ceramic capacitors that will work, they're about 2x the cost but they are extremely reliable. They use this stuff in military equipment and satellites, just how reliable do you need it to be?

Either way it's splitting hairs. Someone who is reasonably experienced soldering with a temperature controlled iron can replace SMT caps easily with very little risk of damage to the PCB. I would not be worried about future replacements, modern good quality parts will last decades easily. If you are going to worry about 40, 50, 80, etc years into the future there are bigger issues. You're likely to find that plastic parts like the case of the machine will crumble to dust and certainly things like CRTs will get hard to come by. There is already virtually nobody manufacturing or rebuilding CRTs of any sort.

 

[uniserver]

yeah like you said, splitting hairs,

i guess nothing lasts forever...

i'll have a look at those ceramic disk caps. See how cheap I can get them for.

 

[uniserver]

http://www.mouser.com/ProductDetail/TDK/C3225Y5V1C476Z/?qs=sGAEpiMZZMuMW9TJLBQkXp%2fN1MIDwoiusPN9BIeM0BI%3d

Multilayer Ceramic Capacitors MLCC - SMD/SMT 1210 47uF 16volts Y5V +80-20%



http://www.mouser.com/ds/2/400/general_B11-23852.pdf

yeah little pricy,

100 : $0.69

Its always kind of confusing when they tell you the life of the cap,

seems that its hardly ever straight forward.

 

[Gorgonops]

If you are going to worry about 40, 50, 80, etc years into the future there are bigger issues. You're likely to find that plastic parts like the case of the machine will crumble to dust and certainly things like CRTs will get hard to come by. There is already virtually nobody manufacturing or rebuilding CRTs of any sort.

We know at least one Commodore PET will be working late in the 23rd Century.

(By virtue of its incredibly heavy steel case no doubt.)

On the subject of electrical parts as "wear items", computers newer than the early 1980s will pose some interesting challenges to future collectors who actually want to run the machines. ICs do "wear out": thermal expansion/contraction, cumulative damage from power supply transients, even the literal "erosion" of the conductive layers over time. Very, very old computers (like the aforementioned Commodore PET) which are constructed almost entirely of "generic" 74xxx series ICs will probably be repairable for a long time, as most of the parts in those machines are still in production *today* and could/can be scavenged from all sorts of places. But you go just a few years newer, when all those discrete ICs get condensed into large-scale application-specific chips that were manufactured *just* for the computer maker to use in a few models, and you're essentially taking about irreplaceable components.

Yes, in theory you could replicate those sorts of chips in a FPGA with enough work (and in fact there are people using FPGAs and CPLDs to generate replacements for some no-longer-manufactured components like SID chips, although the quality of said replacements varies) but that's way, way *way* more complicated than replacing a few caps and a 7400 or two. I sort of doubt that work's going to happen to rescue "random middle-aged Macintosh II series machine XYZ", particularly when you factor in how poorly documented the hardware of those machines tends to be. It's a *lot* of work to make what's essentially a paperweight whether it works or not do its thing.

Anyway.

 

[James1095]

That's certainly a potential issue, although even collectors who use their vintage machines somewhat regularly likely don't put too many hours on the thing. Some parts will fail and fewer and fewer working examples of any given machine will be around as time goes on, but I don't think it's unrealistic to think that a few will still be in working condition 100+ years into the future if taken care of. Given the explosive progress in technology, I wouldn't be the least bit shocked if most of this stuff is eventually replicated in FPGAs or some future technology. Plenty of people already devote time to doing such things just because they can, and I know there is at least one mostly functional Mac Plus FPGA clone. While it's true that Macs were notoriously poorly documented, many parts have been reverse engineered and enough is known to allow fully functional emulators to be written. I have little doubt that just about any ASIC in one of these machines could be reverse engineered well enough to implement it in programmable logic if the need ever arises.