Finally replaced the caps in my Mac classic II

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Finally replaced the caps in my Mac classic II

Postby tezza on Sun May 25, 2014 12:47 am

Sometimes you just have to bite the bullet and fix these things...permanently!
http://www.classic-computers.org.nz/blo ... cement.htm
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Re: Finally replaced the caps in my Mac classic II

Postby SpidersWeb on Mon May 26, 2014 10:59 am

Excellent work.

I find cap removal to be quite frustrating, and have also found it easier to be assisted by a pair of long nose pliers, so my leftovers look quite similar to yours more often than not.
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Re: Finally replaced the caps in my Mac classic II

Postby tezza on Mon May 26, 2014 12:42 pm

Thanks Jono,

The article somehow found itself on Reddit, where a purist or two didn't share the same opinion due to the fact I'd used through caps rather than surface mount. In fact the words were "that is a really shoddy job, not befitting such a historic machine" :roll:

http://www.reddit.com/r/retrobattlestat ... macintosh/

Naturally I don't share that opinion. Replacing like with like is the ideal but given my skill and equipment, the job was good enough for me. Otherwise I'd be staring at one non-working Classic II :)
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Re: Finally replaced the caps in my Mac classic II

Postby SpidersWeb on Mon May 26, 2014 1:43 pm

:roll: it's a Classic II, not an Apple I
Much better like this than not working. Some of my IBM's still have blown mains caps soldered in.
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Re: Finally replaced the caps in my Mac classic II

Postby mrad01 on Mon May 26, 2014 6:49 pm

SpidersWeb wrote::roll: it's a Classic II, not an Apple I
Much better like this than not working. Some of my IBM's still have blown mains caps soldered in.


Agreed. Some people is quite silly. Classic IIs are hardly historic. Even with the SE/30s I have, using non-surface mounts was my only way forward because if they are going in 10 years time, I didn't want to be faced with another recap job. Going through the recap process once on an old board is risky enough.

Here is the result of my own recaps - I used Tantalum caps for longevity and no leak prospects.

http://www.classic-computers.org.nz/forums/viewtopic.php?f=11&t=955#p6176
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Re: Finally replaced the caps in my Mac classic II

Postby Gibsaw on Mon May 26, 2014 8:09 pm

tezza wrote:<snip> In fact the words were "that is a really shoddy job, not befitting such a historic machine" :roll: <snip>

Given all the perfectly good reasons outlined to do the long term viability/storability of tantalums vs electrolytics, combined with this extremely common machine being a good candidate for a first attempt at gaining surface mount repair experience... I will paraphrase and say that was a really shoddy comment for such a historic individual, who has made a very valuable contribution to documenting care of vintage machines.
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Re: Finally replaced the caps in my Mac classic II

Postby tezza on Mon May 26, 2014 8:43 pm

Gibsaw wrote:... say that was a really shoddy comment for such a historic individual, who has made a very valuable contribution to documenting care of vintage machines.

Historical? Well, I am starting to get on in years? :)

Seriously though, thanks for the support. Unfortunately there are some pedantic people out there (they are a very small minorty) who feel it's a cardinal sin to even dare maintain a vintage computer unless you understand digital and analog electronics to 300-level University level, can read and understand a circuit diagram reflected in a mirror in a dim light standing on your head and have a fully equipped workshop with the latest gear. As to swapping chips..well, their opinion is such people should banned from ever opening a computer! No, you must do nothing less than trace the fault from the CPU outwards through the circuits with logic probe and scope until you KNOW exactly the component at fault before touching anything. Anything less and you have no right to be in this hobby at all. :roll:

Not that there is anything inherently long with a robust traced-through diagnosis, but if I suspect a RAM fault and the RAM chips are socketed, I'll sure as hell be swapping them. Life is too short! :)
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Re: Finally replaced the caps in my Mac classic II

Postby tezza on Mon May 26, 2014 8:52 pm

mrad01 wrote:Here is the result of my own recaps - I used Tantalum caps for longevity and no leak prospects.

http://www.classic-computers.org.nz/forums/viewtopic.php?f=11&t=955#p6176

Thanks for that reminder. For some reason I thought you'd replaced surface mount with surface mouth otherwise I would have sought out this reference ( I did know it was in the forum somewhere). My memory is not what it was.

I will need to do my own SE/30 at some stage. tantalums might be a good option if surface mounts still seem a bridge too far. Given their purpose on the machine they should do as well as electrolytics but without the leak/bulge risk. Is there any downside to using tantalums, apart from the fact that when they fail they can explode in a spectacular fashion sometimes?
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Re: Finally replaced the caps in my Mac classic II

Postby SpidersWeb on Mon May 26, 2014 9:36 pm

My only concern with Tantalums would be they tend to fail short-circuit.
But if you used the Mac every few months, you'd likely notice long before that happens or even if it happens. I have 31 year old Tantalum caps in my 5150, all of them intact, but I lost a 486 last week because the heat damaged traces (it didn't pop completely, and the PSU had the worst power protection I've seen).
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Re: Finally replaced the caps in my Mac classic II

Postby Gibsaw on Tue May 27, 2014 9:55 am

tezza wrote:Historical? Well, I am starting to get on in years? :)

Nah, it was just a play on words referring to your hobby.

It's pretty misguided to make that comment referring to a Classic II. He was looking for an excuse to validate his own self-worth with criticism of others. It's a terribly lazy, narcissistic habit - and all too easy from a keyboard. I know it well, and try to keep that particular dog on a leash, myself these days. :)
tezza wrote:No, you must do nothing less than trace the fault from the CPU outwards through the circuits with logic probe and scope until you KNOW exactly the component at fault before touching anything.

And if you'd paid $200k for an Apple I, you would be...but this was a common box with a common fault... as you say... life is short. (and full of compromises, like non-original tantalum vs original but acid-filled electrolytics)
SpidersWeb wrote:My only concern with Tantalums would be they tend to fail short-circuit.

That is definitely a valid concern to be considered amongst the other compromises. I guess you'd need to try and figure out whether a short will do any damage in the location, or whether it just alters behaviour... The explosive failure is a worry too.
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Re: Finally replaced the caps in my Mac classic II

Postby RonTurner on Sun Jun 01, 2014 4:39 pm

I recon the caps are fine, its a Mac so other parts are bound to fail before the caps expiration date, I would never go near a Mac again, would rather have a GS or IIc
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Re: Finally replaced the caps in my Mac classic II

Postby caluser2000 on Mon Jun 02, 2014 3:08 am

You get that type of comment no matter what field your hobby is Terry. Wouldn't loose any sleep over it at all. At the end of the day your system works and that IS all the really matters. At work the guys in the instrument section do surface mount repairs and you should hear some of the comments they make ;) Non obviously worth repeating on a public forum.

Guys like you are an inspiration to many of us so keep up the good work.
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Re: Finally replaced the caps in my Mac classic II

Postby tezza on Mon Jun 02, 2014 11:37 am

Thanks for that. Yes, I'm not losing any sleep over it. With any hobby which involves repair and restoration of old gear be it cars or computers there will always be a wide range of opinions on a repair especially if you make it public. I evaluate criticism on a case-by-case basis. Constructive criticism is not a bad thing and indeed I've learnt a lot from people gently suggesting a better or more efficient way. This is the great majority. A small minority are simply anal or have a holier-than-thou judgmental tone. These I don't respect. Pity, because often they do know a lot and with a personality transplant could actually be quite a positive force in an on-line community.

Eventually they end up leaving or sulking in the corner as no-one responds to their posts or wants to have anything to do with them.
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Re: Finally replaced the caps in my Mac classic II

Postby RonTurner on Mon Jun 02, 2014 2:46 pm

I'm actually impressed that everything you repair works when your finished, especially since your so humble about it while others with your experience (which you say is limited) are blowing things up. I would be happy for you to repair a computer for me (if you where to setup Tezz'a vintage electronics repair shop LTD. :) )

As I said Mac's are not my cup of tea, I just think they look kinda ? [bad words in here] ? I think the miniature monitor is [bad word] and 9 times out of 10 when I see one on TradeMe they are dead (need I say more), the one I was unfortunate enough to win was a real piece of [bad word] and doesn't work, I would have preferred to see Woz build on the GS rather than cut that line and start again, The GS is a better computer with an awesome monitor.

A good appropriate use for a Mac... (The Mac is the one on the Right)
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Re: Finally replaced the caps in my Mac classic II

Postby tezza on Mon Jun 02, 2014 3:43 pm

Things don't always work out. For example...
http://www.classic-computers.org.nz/blo ... oo-far.htm
http://www.classic-computers.org.nz/blo ... sstep.html
http://www.classic-computers.org.nz/blo ... -issue.htm

Not to mention the few Apple II drives I blew up..
http://www.classic-computers.org.nz/blo ... epairs.htm

Lol Gavin, you are being far too hard on baby Macs. Come on, they are cute. :) and iconically 80s. Their little monitors are nice and crisp. Back in the late 80s/early 1990s combine them with a laser printer they won hands down compared to PCs for writing and document preparation...and this is from someone who had to write their papers with WordPerfect 5.1 on a PC. I couldn't afford a Mac.

They are certainly dogged by the capacitor issue now though.
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