Stunt soldering

[R.G.]

I just advised a guy by email on how to replace parts from the top side of a PCB. You can clip off the leads on the top side, then solder to the remaining lead.

You have to do it quickly, so the heat doesn't work its way down the length of the old lead and melt the bottom side too. But it's possible.

A good training exercise is to hold a cut-off resistor lead in thumb and forefinger, and apply a hot, clean soldering iron tip to the other end of the lead. You have a second or so before you have to drop the lead from the heat. But you do have a little time, and if you can make a joint FAST, you can replace stuff on the top of a board.

There is a whole school of do-it-right soldering that would shudder at this, and it's not what you'd do if you had other good options, but sometimes, needs must.

[roberto]

Hi, I share with you the way I do usually:
I weld a little bit of tin to the lead of the component to be welded, then I put it close orthogonally to the lead coming out from the pcb, in order to reduce the contact surface to a minimum (ideally a single point), then heat the component lead to weld the tin and then while eating both leads I add more tin to weld the two together.

This permits to heat the top of the old lead in a short time, without melting the original welding under the pcb.

[Stevem]

I do this all the time in circuit board type amps with plate and grid load resistors.
Usually there is just enough original component lead length to make it into a loop that you crimp around the new lead.
And yes a very hot iron is needed to make the new joint wuthout fully melting the board joint.

[TUBEDUDE]

I've done more "creative soldering" on those damn Classic 30 board jumpers than anything else.

[Leo_Gnardo]

The following requires a sharp pointy wire cutter: solder your new part onto the old part's leads, then snip off the old part. The old part's body & leads provide a little extra heat sinking. Of course make sure the leads you are trying to solder are freshly cleaned of corrosion with a little wire brush or at least scrape with a blade or screwdriver tip. Pre tinning helps immensely. Hakko/Merry makes the kind of wire cutter needed for this. They are small and won't handle thick wire leads. OTOH I've had mine for 15-20 years and haven't broken them yet.

[Reeltarded]

I do this all the time in circuit board type amps with plate and grid load resistors.
Usually there is just enough original component lead length to make it into a loop that you crimp around the new lead.
And yes a very hot iron is needed to make the new joint wuthout fully melting the board joint.

I do the same

[Ken Moon]

This is where a spring-loaded clip-on heat sink is nice (or a roach clip/forcep) - it holds the cut-off lead steady and keeps the heat from melting the PCB solder joint.
The only problem is fitting it in there if the PCB is tightly spaced.
This could be combined with Leo's method of leaving the old part connected until after soldering.
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