Apples in the ceiling

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Apples in the ceiling

Postby tezza on Tue Dec 23, 2014 4:51 pm

Not really classics but I'm glad I managed to save them anyway...
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Re: Apples in the ceiling

Postby glc on Tue Dec 23, 2014 5:36 pm

Capacitors suffer from aging, as you know. the problem is associated with the electrolyte "drying out" if not used for a few years, and then the capacitor(s) suffer from "shock" and then draw high current often with catastrophic results.
So a possible solution is to use a variac to slowly increase the voltage . this helps the mains filter capacitor(s).
For the secondary circuits an external current limiting power supply (or some current limiting inserted into the circuit) is needed to slowly increase the voltage on those circuits.
This can take many hours to days.
There are many articles to search for and read on "reforming capacitors".
I have a variac if you need to borrow one
Hope this helps
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Re: Apples in the ceiling

Postby LilJoe on Tue Dec 23, 2014 6:19 pm

Good job on the repair :). Is the leftover apple gear going on trade me?
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Re: Apples in the ceiling

Postby tezza on Tue Dec 23, 2014 8:04 pm

LilJoe wrote:Good job on the repair :). Is the leftover apple gear going on trade me?

Very likely, at some time early next year. It will be at a very low reserve price.
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Re: Apples in the ceiling

Postby tezza on Tue Dec 23, 2014 8:11 pm

GrantChivers wrote:So a possible solution is to use a variac to slowly increase the voltage . this helps the mains filter capacitor(s).

Thanks Grant. I would consider a variac for a very old and rare computer I might want to restore but for relatively common ones like these I prefer the "turn 'em on and let 'em blow" technique. :) Those AC filter caps from computers of the early 80s are easy and cheap to replace.

In fact in a few of my computers (the TRS-80 Model 4 is one I can think of), I've replaced those old caps as a preventative measure. They always seem to blow.
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Re: Apples in the ceiling

Postby cjr on Thu Dec 25, 2014 9:38 am

tezza wrote:
LilJoe wrote:Good job on the repair :). Is the leftover apple gear going on trade me?

Very likely, at some time early next year. It will be at a very low reserve price.

I see a road-trip up to Palmy in my future. Pretty keen to add a IIe setup to my collection. :D
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Re: Apples in the ceiling

Postby RonTurner on Fri Dec 26, 2014 4:30 pm

Tezza can you PM me a list of which key switches you are wanting (including glued ones) with a postal address and i will post you replacement keyboard switches ready to solder in.

Only if you want them of course, no fee, just free :D
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Re: Apples in the ceiling

Postby Matt on Sat Dec 27, 2014 8:26 am

Good on you Tezza for rescuing these machines. The platinums might not be
particularly sought after by those with museums for houses lol but they are still
classics in my book, just wish I lived nearer you now:-(
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Re: Apples in the ceiling

Postby tezza on Sun Dec 28, 2014 7:11 am

RonTurner wrote:Tezza can you PM me a list of which key switches you are wanting (including glued ones) with a postal address and i will post you replacement keyboard switches ready to solder in.

Only if you want them of course, no fee, just free :D

That would be great Gavin,

I'll send you a PM.
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