Epson HX-20, TRS-80 Model 100 Capacitor Kits

[Marvin Johnston]

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.
> 
>