What's your component removal system?

[Nowhere-Man]

As I stated before, I'm really pretty "green" where printed circuit board work is concerned. Same goes for transistors. The latest reference book I've used is HAM construction related and that also uses point soldering.

Here is where I find printed circuit boards tricky: I tend to use my meter to test for continuity between the upper component leg and its assumed solder point the opposite side of the board. I know that alone isn't fool-proof so I also try to work out the component values too and how the circuit connects.

To get to the point:

The last thing anyone wants to do is lift a track or damage a board. I think the smaller transistor PCB's are easier to simply de-solder but the larger boards you have to angle, get a headlamp on and maybe keep a steady hand. Plus, to repeat, I certainly don't want to be applying the iron an a soldered joint one side of the board and it's the adjacent joint to the one I want to pull. I guess this must happen to people.

On one forum, someone suggested an easy approach is to simply snip out the capacitor from the top, leave enough stump and solder the new component carefully onto that (without actually de-soldering anything). Usually when I solder, I learned to ring my terminal wires to get more surface area and, with enough heat, so far I've had no connections break off. Plus I use a but of surgical spirit first. So probably that way I could make a pretty decent joint.

De-soldering is the usual approach. Yes, I've done it before. I think it helps to be very careful and take your time.

Any thoughts? Any different approaches or personal tips?

[pwdrive]

Sucker, wick, snip and push through, all methods worked for me.

Lawrence.

[Nowhere-Man]

Lawrence, how do you line up your surface and soldered points accurately?

Something I just got curious about and maybe an interesting point to comment on: I heard a lot on forums about multilayer boards. Is this a feature of old vintage radios or mostly a more modern phenomenon? I know this may sound like a stupid question to some but I really know very little about boards. Many of my theory books are from 1940's.
Also do you consider the 1960's boards to be more robust or, on the contrary, not as good?

Pretty much all I encounter are reddish colour with the tracks on the surface.

Incidentally, this use of boards and valve radio continued well into the Seventies in East Germany, Russia and China. It took longer there for the valves to be phased out and, as the sound was good, they just made these hybrid technology sets.

[pwdrive]

Lawrence, how do you line up your surface and soldered points accurately?

Experience.

Sometimes a bright light will help with some boards as the light can shine through, strong light on the component side, observe on the print side using a pointed tool or knitting needle on the component side to find your way around.

Another way is a resistance test between topside component lead and bottom side print, look for 0 (zero) ohms or something very close to it.

Back in the day double sided printed circuit boards were common in some TV's, GEC TV's for example.

Whichever way, you'll soon arrive at the easiest for the situation in hand.

Lawrence.

[ppppenguin]

Apart from a few colour TVs such as the GECs mentioned above double sided PCBs are very rare in vintage (pre 1980) domestic equipment. Multilayer boards are not seen at all.

There are 2 types of double sided PCBs, with plated through holes and without. PTH boards have a conductive sleeve in each hole which joins the bottom and topside tracks. This used to be a complex and expensive processing step so you won't find PTH on vintage domestic kit. What you will find is pins or rivets to join top and bottom side track. Or component legs will do it. All subject to dry joints on both sides of the board.

Desoldering older PCBs can be tricky without causing damage as the copper is often not well attached to the board. Fortunately the tracks are usually quick big and widely spaced so it's easy enough to bodge a reliable repair with wire, often using excess lead length on a replacement component.

Unsoldering an old double sided non-PTH PCB will often lead to the topside track being damaged. For much component removal, from single and double sided PCBs, I usually cut the component out, melt the solder and tap the PCB on the bench. Then clean up with a sucker or wick.

[pwdrive]

GEC running true to form used double sided print in some of their domestic radios, Sony used it too in some of their (non domestic) language lab stuff, I remember them well, pigs to fix...aka look upon all joints as dry joints.

Lawrence.

[Crackle]

It has happened on the odd occasion or score, that I have sucked all the solder of a wrong but nearby component lead. You just have to do it again and then resolder both when you fit the new component in. It is bad enough when a manufacturer locks the component lead in by bending it over, but KB have sometimes had an annoying practice of making a curled end to the lead before soldering, these are really difficult to deal with and straighten to remove the component, these would be best cut above the board and pulled through from below.
What is the opinion on when PCBs became more reliable from point of view of the track lifting very easily. I know the 50's and 60's boards were very delicate. I have not done so much PCB work with 70's and 80's radios.

Mike

[ppppenguin]

I may be wrong but I think the tracks never stuck all that well to the phenolic base material used in most domestic kit. The fibreglass used in most professional kit and some later domestic kit is better. Quite possible that the glues were also improved over time too.

[Old Sparky]

I use a solder sucker, whick is effective on most PCBS, either the SRBP or Fibreglass type, although it struggles to desolder double sided & printthrough boards, and I've yet to find a foolproof method of removing components from these.

[Terry]

You are never going to work on a multilayer board as they just don't exist in the areas that you are interested in working in.

Later boards are often quite simple as the components were all inserted from above - usually manually but (much) more recently by machine - and then flow soldered by passing them across a jet of molten solder with all joints being made in one pass.

This can make component removal quite simple because no wires are bent over on the print side of the board. Apply iron and pull component from above or, even simpler, apply iron and solder sucker - if you are lucky, you will end up with a wire in a hole completely devoid of solder.

On manually assembled/soldered boards, the component leads are bent over on the print side of the board. These can be much harder to deal with. However, if you make sure that your iron is fitted with a nice sharp chisel bit - clean and freshly tinned, of course - try this: apply to the joint to melt the solder - it may be advantageous to add a little fresh solder to help it all to flow nicely - then force the flat side of the bit under the wire, between it and the track, so that you can lever the wire end vertical while also apply downward pressure to the track to discourage it from lifting. Once the wire is reasonably vertical, use the solder sucker to remove the surplus solder.

Afterthought ...

For a cheap, non-destructive way of  practicing, find or buy a piece of veroboard and make artificial 'components' from tinned copper wire - simple 'U' links - and solder them into random places on the board. There is no need to make the usual track cuts, even if one of your 'components' has both ends connected to the same track!

Try both straight-through (being careful not to burn yourself while soldering them and holding them in place!) and captive, where you bend the wires over after inserting them.

Now practice removing your 'components' ...