Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > sci.electronics.design > #434184

Re: Caps on multilayer boards

Show all headers | View raw

I trimmed all the solder-side suggestions :-).  Way back when I was first 
learning how to solder onto pcb's I did some destructive testing on dead 
stuff just to find out how delicate things were, including ripping some 
radial electrolytic caps off of boards.  Now, these boards were 1970's 
vintage, 2 layer, definitely thicker than 1/16", with nice thick, wide 
copper traces and through hole plating.  I just pushed sideways on the top 
of the cap perpendicular to the line connecting the leads, to maximize the 
leverage.  Most times the leads started pulling through the capacitor body 
to give me 1/8-1/4" of slack, and then I could either reach in with little 
diagonal cutters or bend back and forth until the leads broke.  If it is 
working but you have the cap past maybe 30 degrees from vertical and still 
need to pull more lead out of the cap, stop and put a small screwdriver or 
other wedge under the cap on the side you are pushing towards and then push 
some more.  That keeps the leads as straight as possible so they come out of 
the cap with minimal force.  Some were tight to the board or wouldn't loosen 
up, and some of those I still managed to wiggle enough to break the leads 
but some did rip traces and through-hole plating off of the boards. 
Naturally since this was a test I'm sure the success rate was much higher 
than it would have been if I needed to save the boards :-).  You will have 
to look at your board and decide how rugged you think it is.  Multilayer is 
probably a good thing, since the plated through holes should be longer and 
thus more rugged.  Otherwise I think your only other option is to start 
cutting with a Dremel because I don't think you could gnaw through with wire 
cutters.  Practice on a free cap to see how bad it will be.  If you have 
room beside the cap I would use a cut off disc and cut maybe 1/16-1/8" above 
the board, just cutting the side wall all the way around if you can.   Then 
you should be able to pull up on the cap and start the foil unraveling 
inside until you can reach in with small dikes and cut it free.  If you have 
access to one side cut a line across the top and down one side to split the 
can open, and then start peeling.  You're going to make a mess with 
electrolyte and little metal bits on the board so cleanup will be critical 
and may be more effort than just giving in and dismounting the board.  Oh, 
the caps I was successfully destroying were in the 1/4-1/2" diameter range, 
rated maybe 6.3 to 35VDC.  I tried a couple of big AC caps, over 1" diameter 
and rated at least 125 VAC, and the leads and cap construction were way too 
much for the pcb so no joy at all with them.  I ripped maybe a dozen little 
caps off of a couple of scrapped TV boards, so more than one but not a huge 
sample size; it was a few minutes of good fun while I was supposed to be 
throwing away some junk :-).

-----
Regards,
Carl Ijames

Back to sci.electronics.design | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Caps on multilayer boards tabbypurr@gmail.com - 2016-11-07 04:12 -0800
  Re: Caps on multilayer boards Syd Rumpo <usenet@nononono.co.uk> - 2016-11-07 12:46 +0000
  Re: Caps on multilayer boards George Herold <gherold@teachspin.com> - 2016-11-07 06:13 -0800
    Re: Caps on multilayer boards tabbypurr@gmail.com - 2016-11-07 11:48 -0800
      Re: Caps on multilayer boards George Herold <gherold@teachspin.com> - 2016-11-07 13:00 -0800
  Re: Caps on multilayer boards Winfield Hill <hill@rowland.harvard.edu> - 2016-11-07 06:43 -0800
    Re: Caps on multilayer boards tabbypurr@gmail.com - 2016-11-07 11:46 -0800
      Re: Caps on multilayer boards Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2016-11-07 14:47 -0500
        Re: Caps on multilayer boards tabbypurr@gmail.com - 2016-11-07 11:57 -0800
          Re: Caps on multilayer boards stratus46 <stratus46@yahoo.com> - 2016-11-08 01:25 -0800
        Re: Caps on multilayer boards "Carl Ijames" <carl.ijamesXyZZy@ZZxyz.verizon.net> - 2016-11-07 16:11 -0500
          Re: Caps on multilayer boards tabbypurr@gmail.com - 2016-11-08 02:49 -0800
  Re: Caps on multilayer boards Jon Elson <jmelson@wustl.edu> - 2016-11-07 14:13 -0600
  Re: Caps on multilayer boards John S <Sophi.2@invalid.org> - 2016-11-07 18:58 -0600
  Re: Caps on multilayer boards Jeff Liebermann <jeffl@cruzio.com> - 2016-11-08 08:29 -0800
    Re: Caps on multilayer boards tabbypurr@gmail.com - 2016-11-08 13:32 -0800
      Re: Caps on multilayer boards Jeff Liebermann <jeffl@cruzio.com> - 2016-11-08 15:26 -0800
        Re: Caps on multilayer boards tabbypurr@gmail.com - 2016-11-08 15:40 -0800
  Re: Caps on multilayer boards Jasen Betts <jasen@xnet.co.nz> - 2016-11-10 04:29 +0000
    Re: Caps on multilayer boards tabbypurr@gmail.com - 2016-11-12 17:57 -0800
      Re: Caps on multilayer boards John S <Sophi.2@invalid.org> - 2016-11-12 20:23 -0600
        Re: Caps on multilayer boards tabbypurr@gmail.com - 2016-11-13 03:34 -0800
          Re: Caps on multilayer boards John S <Sophi.2@invalid.org> - 2016-11-13 10:17 -0600
            Re: Caps on multilayer boards tabbypurr@gmail.com - 2016-11-13 09:47 -0800

csiph-web