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:
There may be hope for you yet:
Unfortunately not!
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.
2. Is the soldering iron temperature controlled? If yes, raise the
temperature and work fast. Mine runs at 750F (400C) for 60/40 lead-tin.
If no, go shopping and buy a decent adjustable temperature controlled
soldering station. Get a fine tip for fine work, and a thicker tip for
the big stuff (so that the tip doesn't go cold as soon as you touch the
work).
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.
I have terrible eyesight, so I got a used Mantis microscope thing.
https://www.dropbox.com/s/fp88o2rqgr...tis2.JPG?raw=1
I steady my hand on a table or something when I solder, especially
super fine pitch surface-mount parts. The Metcal iron really, really
helps.
You're fine, you're just using cruddy tools.
For really small surface mount stuff, I use a big wedge tip and slop
solder on all the pins, shorting everything, then wick it.
A q-tip and acetone cleans things up pretty.
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.
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.
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
I was afraid of 1206 parts when they first arrived. Now a US8 creates
only mild anxiety. 0805's look gigantic.
Desoldering is trickier than soldering surface mount parts. The part
is a goner, but you don't want to damage the board. My production
people are brilliant, so I let them do the hard ones.
--
John Larkin Highland Technology, Inc
lunatic fringe electronics