One more screwup with the Ace... - test-drb@ccmp.vtda.org

10 Dec 2002

...
 From: "Philip Pemberton"
&lt;philpem(a)dsl.pipex.com&gt;

pete(a)dunnington.u-net.com wrote:
  On things like that, I often don't even try
to rescue any suspect ICs
 or even passives, just cut them off close to the PCB with a very fine
 pair of sidecutters, and then desolder the stub of pin. That's what I've
been doing. I've been desoldering using "Soder-Wick" - I
got a small reel of it for 90p.

  First thing is to make sure anything you remove
is replaced with a
 good quality socket I didn't have any decent sockets - I had to cut two Maplin
"economy DIL
sockets" down to size, fitted two RAMs, then ran out of sockets. In order  to
...
 limit damage to the ICs due to heat, I gave them a
quick blast of freeze
spray and then soldered them. 
Hi
 REAL BAD IDEA! This is just about the worst thing
you can do. Most silicon IC's can take a lot of heat
applied slowly. Thermal shock making a large range
of temperature change is real rough on them and more
likely to fracture the IC or cause the lead seals
to fail.

...

  and if necessary that you can repair any damaged
 tracks with stripped wirewrap wire or similar. None of the tracks are stuffed, the
pads seem to have come up because the
solder wick stuck to them and pulled them up, even though the wick was  still
...
 heated. 
 This is why I never recommend using solder wick unless you
are vary experienced at desoldering. You need to know the right
size and the right touch of applying the heat with this
material. I do 95% of my desoldering with a sucker and
only the last special cases with wick. I have three different
sizes of wick to select for each job. I use different heat
ranges as well.

...

  How adept are you
 with a soldering iron? Six years of experience, three with a Maplin elcheapo, three
with my Antex
XS25 (25 watt). 
 Rework is not the same as soldering. Rework is a special
talent. When you can remove a 25 pin D PC type D connector
...
 from a 4 layer board with half of the pins connect to
large internal traces, without damaging to board, you can consider
yourself a reworker.
 You absolutely shouldn't be using an non-temperature controlled
iron for rework.
Dwight

...

  Did you get the 2114s and Z80 I sent you?  They
should have arrived
 this morning. Yup, they arrived this morning. Fitted them and the random, static
garbage
has been replaced with scrolling garbage. Grr...
I replaced four out of the five 74LS367s too - no dice. The bloody thing is
still being stubborn.

As for your offer to have a look at it, I might just take you up on it.  I've
...
 got a schematic for it (drawn by Bodo Wenzel) for a
clone of the Ace, some
bits are different, 90% of it is the same though.

Thanks.
--
Phil.
philpem(a)dsl.pipex.com
http://www.philpem.dsl.pipex.com/