29 Aug
2018
29 Aug
'18
10:44 a.m.
Well, I rarely use vinegar and much prefer diluted Muriatic Acid
(swimming pool acid to adjust pH), and have done that in this case.
FWIW, a hydrochloric acid based solution is what what many PCB shops
used to clean the tin-lead plating (used as an etch resist) before it
got heated and alloyed into solder.
The bigger problem is waiting too long to repair the problem... like
leaving batteries sitting in a piece of equipment WAY TOO Long so the
traces and PTH DO get badly damaged.
So far, I haven't seen similar damage from leaky caps in other equipment
than the Model 100s and HX-20s. I've also only seen the damage occur
from the Aluminum Electrolytics.
I've used a Weller soldering station for probably 40 years or so and it
works just fine. Recently I bought a Metcal and find the small tip
coupled with the concentrated heat works very well for my purposes.
Soldering 25 mil SMD ICs is MUCH easier to do now. A friend of mine
sells soldering equipment at major hamfests and has most of this stuff
in his inventory. It is especially nice in these days of mail order to
just go over to his house and pick up what I need!
It seems both of us have the experience to do what we do well. I stand
by what I've said... as you do also :). Best regards to you and Brazil!
On 8/29/2018 2:59 AM, Alexandre Souza wrote:
Oh Marvin, you're on your right to disagree :)
Thats why we're here, to
discuss, learn and teach.
The salt...well, the first step of reparing a leaked board is to wash it
in vinegar to neutralize salts/alkali and wash again with
water+apropriate detergent. If you haven't done this, you're not doing a
proper repair job.
"Keep heating", well...I use a weller controlled temperature soldering
station. I can count in the fingers of one hand the tracks I've lifted
on the past 30+ years working with component level computer repair.
"Drill": No way. I'l not EVER do this profissionally. You can argue with
what you want, but I'd NEVER do that. The danger of drilling out the
metalization of a board is too high to use this invasive method. There
was NO board I couldn't clean a hole propperly. Ever.
I respect your experience, but believe me, I've done repairing on some
hundreds of old "irreparable" computers. People only bring things here
when no one wants to play anymore. I'm the "last mile" of retro
computing repair here :)
Take a look at my sites:
http://tabajara-labs.blogspot.com
http://tabalabs.com.br
I'm sure you'll have some fun with some repairs I've done :o)
Greetings from Brazil!
Alexandre
2018-08-29 4:31 GMT-03:00 Marvin Johnston via cctalk
<cctalk at classiccmp.org <mailto:cctalk at classiccmp.org>>:
Hi Alexandre,
I very much disagree with your NEVER use a drill comment and add
more solder w/heat for several reasons, valid at least for someone
who knows what they are doing.
First, the little information I could find on the solder corrosion
caused by leaky electrolytic capacitors suggested a salt compound is
formed that mere heating and adding solder won't remove. I'd love to
hear more about this problem and what this residue actually is!
The problem with "keep heating" is the bond between the copper and
the substrate is substantially weakened by heat making it MUCH
easier to damage the PCB by lifting traces, remove the plated thru
holes copper, etc. Not sure about high temperature substrates such
as Kapton, but that isn't what we are talking about here.
Also notice I used the words "pin vise" and "#62 drill." The idea
is
to use a drill small enough that will remove the residue from the
hole having enough clearance without removing the copper from the
PTH. It seems reasonable once there is a hole to solder again and
see if the hole can be cleaned out.
We lost power at the house today (electric company maintenance) so I
didn't have a chance to play around more. Also I do have
"professional" experience with printed circuit boards as I was a
field engineer who worked in many printed circuit facilities around
the US, and owned my own PCB manufacturing company in a previous life.
All that said, I still think using SMD might be the safest way to
replace the caps while minimizing the chance of damage to the
printed circuit board.
Marvin
On 8/28/2018 2:39 AM, Alexandre Souza wrote:
never, EVER use a drill. add more solder and keep heating the
corroded solder, it will eventually melt and mix with new solder.
using a drill will destroy the board.
Enviado do meu Tele-Movel
On Tue, Aug 28, 2018, 03:38 Marvin Johnston via cctalk
<cctalk at classiccmp.org <mailto:cctalk at classiccmp.org>
<mailto:cctalk at classiccmp.org <mailto:cctalk at
classiccmp.org>>>
wrote:
? ? Since I have at least four Model 100 and HX-20s, I've
decided to just
? ? replace all the aluminum electrolytics before repair
becomes much more
? ? difficult. So far, I see the project as fairly easy
depending on how
? ? bad
? ? the corrosion from the leaking caps is.
? ? Is anyone interested in buying a kit or two of the
capacitors? I'm
? ? guessing buying the parts from DigiKey at low quantity
prices will
? ? result in about $3.50 or so for the bag of about 13
capacitors. US
? ? postage will probably run a couple of dollars or so, but I
can also
? ? bring them with me to VCFMW. I'll be ordering what I need
unless I hear
? ? others might want the kits as well.
? ? On a similar topic, has anyone given up on cleaning out the
corroded
? ? plated-Thru-Holes, and just soldered on some SMD caps? If
so, how
? ? did it
? ? work out?
? ? Finally, just some observations on the corrosion. I finally
found some
? ? information about the corrosion caused by leaking aluminum
caps. It
? ? sounds like the leaking fluid, besides possibly damaging
the copper
? ? traces, also does something to the solder in the PTH such
that a
? ? soldering iron won't melt the solder. Right now, the solder
doesn't
? ? want
? ? to melt so I will use a pin vise and about a number 62
drill or so to
? ? hand drill out the PTH solder.