[Elecraft] Re: OT: Removing Solder Through Plated Through Holes

[Don Wilhelm]

Jim,

You look at the schematic and find *all* the paths connected to that 
component location - then you check for continuity from the potentially 
damaged pad to all the other locations.  Even if you don't know how to 
"read" a schematic sufficiently to identify the circuit function, it can 
still tell you 'which is supposed to be connected to what', and that is 
what you must check.

With 2 sided boards, sometimes you can tell by looking at the board and 
see the traces coming from the potentially damaged hole - if the circuit 
is not complex, all the wiring may be all on one side and all you need 
to do is to be certain to solder that side containing the PC board 
traces.  Normally on 2 sided boards, an effective repair is to solder 
the component lead both on the top and the bottom.

If you are dealing with a multilayer board - the process of using the 
schematic is the same, but the process is more complex since there can 
be a path from each layer.  To repair in this situation, one would run 
discrete wire point to point for the entire network containing that hole 
(it is the only certain thing to do other than replacing the board).

Bottom line (may be 20-20 hindsight) - use a drill *only* on single 
sided boards or boards that are known to *not* have thru-plated holes.  
Many holes are used as a continuation of the circuit from one side of 
the board to the other (known as "via holes" and those holes can serve 
double duty as a mounting place for a component lead.

All such damages are repairable with the possible exception of carefully 
laid out VHF/UHF circuits - even if the repair is a PITA.

73,
Don W3FPR

jimimaxi2 at comcast.net wrote:
>
> If I have done what you say I shouldn't , meaning take a hobbyist 
> drill to widen a solder-filled hole, how do I check if I have broken 
> the connection between top side and bottom side?
>
>