[tlug] Mo' bulged electrolytic capacitors

[Jim <jep200404@example.com>]

"Lyle (Hiroshi) Saxon" wrote:

> Jim wrote:
[>> Lyle wrote:]
> 
> >>one of them [bad cap] leaked a very dark 
> >>brown goo that flowed about 8cm across the main circuit board - that's 
> >>probably the detail that stopped the board from functioning.
> 
> >The presence of the goo on the board is likely _not_ what caused 
> >the board to fail. The _absence_ of the goo from the inside of the 
> >cap is what caused the board to fail. _Most_ of the bad caps I've 
> >seen did _not_ leak. 
> 
> I know.  I meant that the trail of goo was evidence of the specific 
> capacitor that probably caused the malfunction

One can not make such a specific conclusion either, even with 
the "probably" qualification, especially since you wrote: 

> nearly all the capacitors (except the smallest ones) have ballooned tops, 

Most of the bulged bad capacitors that I experienced, 
did not leak. 

> >People can solder those small pads with no difficulty. 
>
> Okay.  But why bother when you can trash a rotten design and buy a
> better one for cheap?

Oh, you didn't like the answer, so you changed the subject. 
Hasn't that other subject also been answered before on TLUG or COLUG? 

Often, one is itching to upgrade anyway, and this is the excuse. 
Also often, there are mundane reasons to fix the board if you can. 
Some of those mundane reasons are time. It can be quicker to fix the 
board than to get a replacement. (That someone does not have the 
skills, equipment, or parts is a separate issue.) Sometimes because 
of an odd size or shape motherboard, replacements are hard to find. 
Sometimes, expensive software is keyed to something rather unique 
(perhaps serial numbers, perhaps just drivers) of the board, making a 
board swap super expensive, or if the software vendor is out of 
business, very painful. By the way, how good are the caps on your 
new motherboard? How do you know. It's OK to upgrade just because 
you want to. 

By the way, this is being written on a computer with a motherboard 
that had bad caps. 

> Actually, I didn't mean that the heat would damage the capacitors,

Of course not. The capacitors are dead, junk, kaput. 
It's quite acceptable to destroy bad capacitors when removing them. 
It never occurred to me that someone would worry about damaging 
already bad capacitors. 

> I meant that the heat could damage the very small copper pads on the 
> board, which can separate from the board is you overheat them for too 
> long.

You can still do that if you are aggressive enough, but materials 
have greatly improved. I've had no problem with this. 

> (Based on experience with 1980's circuit boards, so maybe it's 
> not relevant any longer

Timid people who know that too much heat can delaminate the copper 
from the board, often provoke such damage by trying to compensate by 
using an iron that's not hot enough. The longer time needed causes 
more damage than a quick hot iron. It's better to hit it hard and quick. 
This was true even in the 1970s. 

> By the way - and I asked you this before and received no answer - which 
> specific "many many" "prestigious high-quality" manufactures are you 
> referring to? 

I wasn't referring to any specific manufacturers, 
because the problem is so broad. Yes, it's that bad. 
You can do your own searching on the web to confirm this. 
Interesting key words are capacitors, espionage, bulged, 
motherboard, Japanese, and Taiwan. Explore. 
It'd probably be easier to provide a list of boards 
that are known to _not_ have the problem. 
(No, I'm not going to supply such a list.)

> Specific manufacture[r]s and models would be much 
> appreciated by everyone who regularly buys used equipment! 

The problem is so broad, that there is no such list. 
Even if there was such a list, it would be of little use. 
Look at the condition of the caps, not the name on the box. 

Read all the old threads that I posted the URL for. 
Google is your friend. So is Wikipedia. 

> Generalizations (many many) are of no use whatsoever! 

A very broad and useful generalization is that 
all motherboards since the late 1990s are suspect. 

> Also - out of curiosity - what is the supply of used computers like in 
> your area?  Are they readily available or slightly elusive?

They are readily available.