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Compaq Portable Power Supply

KevinO

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Apr 13, 2012
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Des Moines, IA USA
I've got 2 of the original Compaq "luggable" Portables. Both have bad power supplies. I pulled the covers and the capacitors look horrible. Not the usual bulging that you would expect to see, but actually corroded like an old car battery! Has anyone had success repairing these power supplies? Are there schematics available somewhere?
 

KevinO

Experienced Member
Joined
Apr 13, 2012
Messages
328
Location
Des Moines, IA USA
I've got 2 of the original Compaq "luggable" Portables. Both have bad power supplies. I pulled the covers and the capacitors look horrible. Not the usual bulging that you would expect to see, but actually corroded like an old car battery! Has anyone had success repairing these power supplies? Are there schematics available somewhere?

I have since read some other threads about the tantalum capacitors in these failing at a high rate. Strange, isn't usually just electrolytics? It was those that were nasty looking. I suppose I'm going to have to take the thing apart down to nothing to get this PS (that stands for Power Supply...really!) and see what there is to see. I'm just worried about whether or not it's worth trying, since I've had a commodore 128 power supply on my bench for several days that I can't seem to fix and it has only 20 parts!
 

KevinO

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Apr 13, 2012
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Des Moines, IA USA
Can you post some pictures of what you're dealing with?

I'm at work at the moment, but maybe I can get to it tonight, take it apart and see what's what. Then I'll post some pics. Where I was going with my general question is that if they are hard to repair, as switchers often are, I don't want to order and install $25 worth of capacitors (those big electrolytics can be expensive) if it's not likely to work anyway.
 

barythrin

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That's the way my new MSI motherboard looked too btw. Almost all caps were leaking black crap on top and all over them. Normally I've just seen a hole or a bulge but these seem like what you saw. I didn't notice any damage on the board from mine but naturally we're talking apples and chickens. I would think in your case as long as it didn't damage the pcb it might be salvageable however I don't know if multiple bad capacitors would cause any voltage increases or unseen damage to other components.
 

Chuck(G)

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Electrolytics have a limited service life--I don't understand why people seem to think anything electronic will last forever. Electrolytics use a paste layered between sheets of (usually) aluminum foil (older caps may use tinfoil). Eventually, the electrolyte either dries out or gets overheated or corrodes the aluminum and leaks. Solid electrolyte caps are new and so for the most part, the greatest selection is in SMT types.

Older tantalums do fail because again, they use a paste electrolyte. New tantalums do not have this problem, as the electrolyte is solid. When tantalums fail, the failure is usually noisy--usually a sharp "crack" or "bang" like a small firecracker. Most electrolytics fail silently.
 

KevinO

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Messages
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Location
Des Moines, IA USA
Electrolytics have a limited service life--I don't understand why people seem to think anything electronic will last forever.

I sure hope I didn't give the impression that I thought that! But I did not know that older tantalums used a paste electrolyte, so I appreciate your sharing that.

I'm not going to get back to this for a couple days, but I will try to get it apart this weekend and get a better look.
 
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