Circuit Lake

If you want to learn Reverse Engineering you can use photoshop as aid tools. For example, This 12-keys keypad failed after years of daily use. No schematic or replacement parts from the original manufacturer. The only option was to replace it with an off-the-shelf telephone-style keyboard.Following the maze of each and every PCB track in a circuit is boring and error-prone, so here is the easier way to get the job done. (more…)

By Mike Byrne

INTRODUCTION
All IC processes have an intrinsic breakdown voltage associated wlth them. and this results in a maximum voltage stress which can be applied to any device fabricated on that process. Aa a result, all IC manufacturers give an Absolute Maximum Ratings specification for their devices. This generally gives the maximum voltage which can be applied to any of the pins on the device. Overvoltaging a device means that stresses or voltages in excess of the absolute maximum ratings are applied to the device. This application note deals in particular with overvcltage of the power supply inputs to CMOS and linear-compatible CMOS devices.
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by Alan Winstanley

De-soldering is required when electronic components need to be removed from a circuit, usually because they are faulty. It may sometimes be necessary during testing or assembly, if a wrong part has been fitted or a modification has to be made. In the field, it’s not uncommon for faulty electronic components to be swapped out, or poor joints (perhaps “dry” or gray joints) to need re-making properly, months or years after manufacture. Experienced engineers can often diagnose a particular faulty joint immediately, because they may have seen the same problem on similar electronic equipment before, especially if the equipment has a “reputation”. A proper desoldering technique can soon be acquired with practice - all you need to do is buy some scrap boards to have a go with, and desolder to your heart’s content!

The next photo sequence illustrates the basic steps for desoldering a printed circuit board, in order to remove a faulty part. Both the technique for using a desoldering suction pump as well as desolder braid are illustrated.

Remember - Practice makes perfect.

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(1) The two solder joints to be desoldered, to enable a faulty electrolytic capacitor to be removed from the printed circuit board.	(2) If using a suction-type desoldering pump, apply the soldering iron tip first to melt the solder joint (say for 1-2 seconds). Ensure the spring-loaded desoldering pump is ‘primed’ and ready to go…
(3) The PTFE nozzle of the desoldering pump is applied to the molten solder and the spring-loaded plunger is then immediately released, drawing the molten solder up into the pump. Remove the soldering iron tip. Repeat the process if needed. Handy tip: sometimes it helps to add some fresh solder and then desolder the whole joint.	(4) The first p.c.b. joint, now desoldered. The second joint will be desoldered using traditional desoldering braid.
(5) Select a suitable width of desoldering braid, and press it down onto the COLD joint using the hot tip of the iron. A flat soldering iron bit is preferable.	(6) The molten solder is drawn up by capillary action into the desoldering braid. Take care not to overheat the board (the p.c.b. copper track may lift off), nor ‘drag whiskers’ of solder over the board, nor let the braid solidify onto the joint! Remove the braid while the joint is still molten.
(7) The faulty electrolytic capacitor dropped out of the board after desoldering. Sometimes, it may need persuading with pliers…. but don’t overdo this or you risk damaging the copper tracks on the PCB.	(8) Close-up photograph of both joints, now desoldered and ready for the replacement component to be fitted.

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by Alan Winstanley

Soldering is a delicate manual skill which only comes with practice. Remember that your ability to solder effectively will determine directly how well the prototype or product functions during its lifespan. Poor soldering can be an expensive business - causing product failure and downtime, engineer’s maintenance time and customer dissatisfaction. At hobbyist level, bad soldering technique can be a cause of major disappointment which damages your confidence. It needn’t be like that: soldering is really easy to learn, and like learning to ride a bike, once mastered is never forgotten!

These photos illustrate the basic steps in making a perfect solder joint on a p.c.b. If you’re a beginner, our advice is that it’s best to practice your soldering technique using some clean, new parts with perhaps some new stripboard (protoboard). Be sure to avoid using old, dirty parts; these can be difficult if not impossible to solder.

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(1) Printed circuit board copper tracks must be clean to begin with, especially if they’re not previously “tinned” with solder. Clean any raw p.c.b. copper tracks gently with e.g. an abrasive rubber block available from electronics suppliers.	(2) Clean the iron “bit” (soldering iron tip) using a damp sponge. The soldering iron featured is an Ungar Concept 2100 Soldering Station.
(3) A useful product is Multicore’s Tip Tinner Cleaner (TTC) - a 15 gramme tin of special paste which cleans and “tins” the soldering iron iron, in one go. New tips must be tinned immediately when used for the first time.	(4) Insert components and splay the leads so that the part is held in place.
(5) It’s usually best to snip the electronic component wires to length prior to soldering. This helps prevent transmitting mechanical shocks to the copper foil.	(6) Apply a clean soldering iron tip to the copper solder pad and the component lead, in order to heat both items at the same time.
(7) Continue heating and apply a few millimetres of solder. Remove the iron and allow the solder joint to cool naturally.	(8) It only takes a second or two, to make the perfect joint, which should be nice and shiny. Check the Guide for troubleshooting help.
(9) An example of a “dry” or “gray” soller joint - the solder failed to flow, and instead beaded to form globules around the wire.

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