Ugly soldering (HP 67 internal)

[teenix]

(11-12-2016 01:47 PM)n1msr Wrote:  The connectors are plug-in joints, as rightly highlighted by damaltor.

One of the connectors has gone - I must have lost it in the fight with the board and the soldering iron.

Please be aware that handling the board incorrectly may cause static damage to the IC components which may not be repairable. Always handle the board by the edges. Any wires connected to a circuit board requires extra careful handling or you risk damaging other connections, especially on older boards.

If the connector has totally gone due to the soldering attempt, you might need to check where it came from and make sure the circuit board tracks have not peeled away from the board because of excess applied heat.

If that looks ok, then you may be able to replace the connector with the IC socket connector mentioned by damaltor.

To do this, the hole where the original connector came from must be free from excess solder so that the new pin can be inserted. You can get "solder wick" from hobby suppliers which will help clean things up. If you do not think it is possible to clean up without damaging the board with excess heat then don't do it or your problems will get worse.

You can break one of the mentioned socket pins out of the plastic housing. They are a press fit, so can be pushed out. Insert it into the hole where the original connector cam from and solder that to the board from underneath. Then solder the wire to the top of the connector.

As already mentioned, practice a bit. Vero board available from hobby suppliers where you get the IC socket from would be cheap and good to practice on.

If it is not possible to reinsert a connector, then you could have it professionally repaired but obviously, at a cost.

As a "dodgy" fix, you could also look under the board and see where the connector was originally soldered, and solder the wire end to that spot. This method should work, but is a bit messy and may require the wire be lengthened, and may cause problems fitting back into the calculator casing

An easy solder method is first to make sure the solder tip is clean and free from excess solder. (A little bit is good) A tip size 3-5mm should suffice.

Pre tin the wire end before soldering to the board.

Don't put new solder onto the solder iron tip then move the tip to the wire end or the solder flux will burn away beforehand. The solder needs its internal flux to help combine it with the wire.

Having said that, it is good to have a "little" bit of solder on the iron tip to help with heat transfer to the wire or circuit board.

Hold the soldering iron on the bare wire end and a few seconds later push the new solder to where the solder tip meets the wire. The solder will melt around the wire (if it is clean) with the help of the flux. Don't take too long though. As soon as the solder "takes" pull the iron away and perhaps blow on the wire to cool it in case the insulation gets a bit hot.

Pre tin the top of the connector in the same way - only just enough heat heat though.

Now hold the wire end, pointing vertically down, onto the connector.

Put the solder iron tip (still with a little bit of solder on it) to where the wire rests against the connector and the two will melt together. Once this happens pull the soldering iron away and again blow on it to cool quickly.

Hopefully all fixed :-)

cheers

Tony