23 Dec
1998
23 Dec
'98
2:16 a.m.
Hans Franke wrote:
Un-etching?
For unsoldering if this is what its about, I developed
a well working solution. take a vertical mounted vice
insert the PCB with one edge, component face down and
take one of these 'super hair dryers' (as used for
removing old paint from windows) and fry the backside.
try to sperad the heat over the whole board - just like
hair drying. With the other hand (you need only one hand
to hold the fan) tip onto the unfixed end of the board
to allow the components to drop out of the holes. If a
part is fixed thru bended wires/pins, you might need to
help with a screwdriver - ACHTUNG - more heat will NOT
help :)
I used this method on literaly hundreds of boards to free
components for reuse. During on time around '86 or '87 I
unsoldered about 60 MB in 41256 chips from old PBX boards
(At this time 41256 where still valuable in PCs :) I had
no memory shortage back then :). At time I build an almost
automatic unsoldering work bench ... I took 4 old 220 V
coils from power relays (?) fixed them in th corners of a
wooden case (an old drawer) and build a framework of light
wood with 4 thick nails to go inside the coils. Atop the
frame the PCB was layed face down. Now, if I powered the
coils, they lifted the frame (almost like a maglev train
huh :), and, since it was 220V 50 Hz shaked it with a soft
frequency of 50 Hz - now I only had to move the heating fan
above and wait for the dropping RAM chips.
Of course, if you use a vice to fix the PCB _and_ you want
to keep the PCB you should fix it with an additional layer
of soft tissue (or better rubber), and don't shake to hard.
No, un-etching was the term I used. Kits used to start with a
sheet of material coated with copper and (usually you applied it
yourself) wax. You scraped off wax where you didn't want the
traces to be, then you dipped it in acid to remove the bare
copper. You'd find out quickly whether you'd applied or scraped
the wax properly. Un-etching would imply putting the copper back
on the board to return the kit to its virgin condition.
Stripping components from a board is easy. I was doing that
before Clinton seduced his first cheerleader in high school.
--
Ward Griffiths <mailto:gram@cnct.com> <http://www.cnct.com/home/gram/>
WARNING: The Attorney General has determined that Alcohol, Tobacco,
and Firearms can be hazardous to your health -- and get away with it.
> > Not having an assembly manual for any
of the early 8bit kits (altair, imsai,
> > etc...) I was wondering about the experiences/success of anyone
> > DISassembling one *back* to kit form. Anybody?
> You cannot be serious about that. The
soldering and board etches are not
> always the best quality and desoldering all them holes is a major task
> never mind the potential of cooking a soldered in componenet..
I've
built three altairs (8800A or earlier) and they were not fun to
assemble but it saved a bundle.
Un-etching a board is a challenge I would not accept.