Broken soldered joints on circuit boards

[Matty F]

I had a lot of electrical problems with my car for years, mainly the headli ghts going off for a second, and the wiper wiping when it was turned off. T he symptoms pointed to a random open circuit. I searched all the wiring and relays etc. Eventually the problem got so bad that the car was undriveable . I couldn't get it out of park, and the starter wouldn't start. I asked ev eryone and searched everywhere.

I'll ask again, what is controlling all those devices? The answer of course is obvious, the body computer, as in most modern cars. But no faults were logged. The answer again is obvious when I think about it, the earth for th e computer was faulty, therefore it couldn't log faults. Here is how the co mputer circuit board is earthed:

The circuit board earth is soldered over the mounting bolt that is screwed into the computer case. And the solder has cracked right around the bolt. D oes that matter? You bet it does. Through that earth passes all the current to drive the computer, and the current to drive dozens of relays. Now this is a very basic design fault. Most circuit board faults are caused by sold ering a large component to the board, and that component flaps around for y ears until the solder breaks. In this case the circuit board is flapping ar ound the mounting bolts, because there is an 84 wire cable attached directl y to the board.

I just soldered it properly and the car is now fine. If I have any more pro blems I will run a flexible wire from the circuit board to earth (like the manufacturer should have done). I suspect all cars with computers of this t ype will fail after a few years. You don't have to replace the computer! Ju st look at it! And a minute with a soldering iron will fix it.

The same goes for television sets, remote controls, VCRs, stoves, all of wh ich have had broken soldered joints and which I have fixed. So if something doesn't work, get out a magnifying glass, and look first at the largest co mponents on the board and the external connections, for broken soldered joi nts.

[Tim Watts]

On Friday 01 November 2013 04:59 Matty F wrote in uk.d-i-y:

I fixed a TV once where the line transformer had done exactly this.

Who relies on solder to hold head components - Heathkit stuff used to use machine screws and nuts to hold transformers to the PCB.

[Andrew Mawson]

That's a classic vibration fatigue failure, much more prevalent with 'lead free' solder than the original 60/40 tin lead stuff. For this reason 'lead free' is now not used for highly critical kit.

AWEM

[Brian Gaff]

You can add Washing machines to that list as well. My old Service, now deceased due to lack of spares soldiered on (soldered on?) after its circuit board was resoldered.

I think this is what happens when hasty decisions are made without anyone thinking about the environment these things live in. I had a VCR back in the day, which cut out for no apparent reason. This turned ot to have been overcooked silicon diodes when the board had been made. Very thick wires and the plastic boddy slightly melted and with heat cyclingover the years the internal connection inside the plastic was just touching rather than properly connected. Cange the diodes and all was sweetness again. Brian

[Matty F]

The computer was made in Portugal by Ford in 1997. Isn't that before lead free solder?

[tony sayer]

Nothing new .. I had a very odd problem on the Audisaursus just a dry joint like that, soldered and fine again.

I reckon its just sometimes quicker to re-work all the joints on a board than try to find them;!...

[Huge]

That's what I did, 3 tellys ago. I gave up trying to find the dry joint in the power supply board & just remade all the joints.

[The Natural Philosopher]

I had te same on a hired Ford Monedo once. The whol dashbaor 'went out'

I phoned the supplied 'roadside assistance' chap and he said 'oh they all do that. Bad earth on the PCB. jut keep driving it - as long as you can work without a fuel gauge, temperature gauge, rev counter...you will be all right..' :-)

[The Natural Philosopher]

I did exactly that on an old colour TV. yelets through the board were causing intermittent issues. I soldered one or two that showed issues when prodded, then thought 'sod this for a game of soldiers, I'll let the EHT die down and resolder every single one there is'.

Result was the 13 year old ex rental TV sold(i)ered on another 5 years before a direct lightning strike ruined it...didnt owe me ANYTHING by then.

Done similar on the freelander - a corroded socket that I simply couldnt find a spare for on the overhead light cluster showed up. 'Proper' repair would have meant a whole new wiring loom and dismantling half the car interior to replace. Totally satisfactory solution was to cut the socket off altogether and solder the wires directly to the board. All works perfectly :-)

[The Natural Philosopher]

That's three of us then. Remind me of the time I first encountered the 'service department' of a small audio company I once worked for. I was impressed with the repair rate of the boards especially since the girls dong it did not appear, to me, to be capable of understanding how the circuit actually worked..

"Oh no we don't, we just unsolder all of these' pointing to the power transistors and drivers 'and these, if they are brown' (pointing to the current limiting resistors) 'and replace with new parts and a new fuse and put them back on the production line to test' 'And what happens to the stuff you removed?' I asked..'HE tests them' and HE chipped in 'and if the aren't f***ed they go onto the production line to be used in new boards' 'and what happens to the customers amplifier itself?' 'We just take new or repaired boards off the production line and fit them in place of the old?'

It was a slick efficient operation turning round dozens of blown power amplifiers a day with almost no skill required at all. At one level I was appalled, at another I was rather impressed.

[Bill]

In message , Matty F writes

I've probably told this before.....

To dehumidify while building the boat in the garage we took the door off the old fridge, bent a sheet of brass into a u shape to hook onto the bottom of the ice box, and soldered a large number of short lengths of copper pipe so that they all dangled from it. The gaffer-taped poly sheet directed al the water into the salad tray at the bottom, which I emptied daily.

The job lasted 5 years and at the end the copper to brass soldered joints all looked crystallised, with several pipes falling off.

All with lead solder.

[Andrew Gabriel]

I made some heat pipes recently (amazing things to play with). I soldered them with lead-free solder (as kids play with them). It will be interesting to see how long they last. Refrigeration pipework always seems to be brazed, and I'm guessing there's some good reason for this.

[tony sayer]

Can you say who it was .. Quad for instance?...

[Tim Streater]

And what was it about the design that caused so many parts to go t*ts-up?

[The Natural Philosopher]

a small electronics company was in fact PACE - Parmee Acoustics, Collins Electromagnetics registered under the corporate name of Michael Mouse Electronics.

Which tells you nearly all you need to know. The rest you can find in the records at Companies House...and you can draw the inferences from that.

[The Natural Philosopher]

The fact that Richard Parmee was a very poor designer of cheap power amplifiers.

And sold an awful lot of them.

[Bill]

In message , tony sayer writes

I fixed a TV, much to my amazement, a few years ago by turning the lights out, tapping the pcb and seeing which joints had arcs around them.

A thought for you Tony. Motorola's 6 unit GP chargers use a smpsu that has 2 heavy components in it. A toroidal transformer on a large ferrite core and a large electrolytic. If you ever have a duff psu check these out, they cause 90%+ of the faults, failed joints galore. A bit of hot melt glue would have saved most of the problems. There again I remember the day when large electrolytics had mounting lugs and weren't just held down with the 2 leads.

[tony sayer]

Never seen one around!. I thought you meant HH the power amp maker dreadful sounding things never did like them...

[tony sayer]

In article , Bill scribeth thus

I try not to .. but I keep muttering they don't make 'em like they used to a lot these days;!(...

[The Natural Philosopher]

they were contemporary with HH. IIRC the amps were 19" rack mount bricks with MM on the front in all black.

cheapest 2x100W you could buy at the time.

They also did the cheapest mixing desk you could buy.

There is not even one image I can find of their products on google, which shows you how bad they were.

There is however one of the thing I designed whilst working for them