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

[Alexandre Souza]

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>
:

> 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>> 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.
>>
>>