On Sun, 7 Oct 2018 20:06:40 -0000 (UTC), Cursitor Doom
wrote:
On Sun, 07 Oct 2018 10:36:05 -0700, Jeff Liebermann wrote:
1. How many watts is your soldering iron? It looks like the mess made
by too low power or too fine a tip. 75 watt seems about right.
I have 15W, 25W, 40W and 80W irons. This atrocity was carried out with
the 15W one which has a pointed tip for some reason.
There's your problem. 15 watts is far too small for the heavy gauge
wire you're using. The pointed tip is too small to retain enough heat
to solder some of the larger parts in your photos. You also didn't
bother to disclose whether you're using a temperature controlled
soldering iron or a crappy wood burner. I'll guess(tm) a wood burner,
probably with unplated rusted iron tips that can't be cleaned, wetted,
or tinned.
If my guess(tm) is correct, you don't have a prayer making a decent
solder connection even with a keen hand and a steady eye. The trick
to soldering is to use decent equipment, a clean tinned tip, and the
correct temperature. Use a hot tip set to the temperature for the
type of solder you're using. Get the work hot quickly, solder
quickly, and remove the iron as soon as possible. If you use a stone
cold 15 watt iron, you'll end up lingering on the joint for far too
long, which will dramatically increase the size of the heat affected
zone, which will likely burn the PCB, vaporize the flux before it's
needed, and possibly run some parts. By fast, I mean something like 1
second or less.
You're very kind in attributing this train wreck of a repair to my having
the wrong tools, Jeff. Sadly I don't believe it's the case. This kind of
work requires a steady hand and a keen eye and I possess neither.
A friend of mine lived long enough to get Parkinsons Disease. Near
the end, his hands shook bad enough that soldering was impossible.
However, before that, they were steady enough to hold the iron, but
not the work (wire and components). So, he build a fixture with an
articulated battery terminal clamp to hold the joint together while he
soldered it. For the soldering iron, he build something similar that
only required that he leaned on the iron to push it into the
connection. The process wasn't graceful, but it worked.
If you have vision problems, get a proper magnifier or microscope. My
eyesight is becoming bad enough that I need to use a microscope for
SMD work, and a magnifier for ordinary work. Good lighting also
helps. My soldering would look as bad as yours if I didn't have these
aids.
If you're not sure that decent soldering equipment will improve your
miserable soldering, then borrow someone's decent equipment and try it
for a day or three. If it's hopeless, look into the possibilities of
using a soldering robot:
https://www.google.com/search?q=soldering+robot&tbm=isch
https://www.youtube.com/watch?v=BJMnk7maUVs (1:33)
3. Are those 3300uF 25V caps 85C caps or 105C? The photo looks like
85C. If so, they'll last about 6 months inside a hot oscilloscope.
I followed the original spec as far as possible. The originals were
5500uF, 30VDC and 85C. I couldn't get the right capacitance within the
space available so used 33's in parallel. The old 85C's lasted for
decades so your 6 month assessment may be a bit pessimistic.
I had problems finding can type electrolytics so I used axial leaded
electrolytics as a substitute. They fit inside the old can, so I just
ripped out the guts from the defective capacitor and crammed the axial
caps inside. I used 85C caps which lasted about 6 months. I replace
them with 105C caps and they've been running for about 2 years.
4. Clean the enamel off the wires with sandpaper before you solder.
Tin the wire ends before attaching to a lug or PCB rivet.
Yes, I did do that. I know what I *should* do but it doesn't help.
If you know it's not going to work, why bother doing it? You're not
going to get a decent solder connection if it's covered with melted or
burnt insulation, no matter how nice your tools or technique. A
decent solder connection requires that ALL the parts of the puzzle are
clean before you apply heat and solder. Do it.
Also, if you don't have a hot air SMD workstation, this might be a good
time to get one because they often include an adjustable temperature
controlled soldering iron.
Can you imagine the carnage I'd leave behind attempting SMD stuff?? :-D
It takes a bit of practice, but once you understand how it works, it's
quite easy. Soldering SMD devices with solder paste is easy because
the part self-aligns itself on the pads once the solder melts. There
are plenty of videos on YouTube showing various ways to use a hot air
SMT desoldering station. Instead of declaring defeat and surrendering
before you start, watch a few and decide if you can handle it.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558