And today's little bit of time-wasting lead-free nonsense ...

A big heavy Quad sub. It's been so long since I've seen anything new with the Quad name on it, I wasn't even sure that they were still going. Anyway, this thing always worked in that the amplifier kept producing output, but there was, at the very least, a background 'rustle' and at worst an alarmingly loud crackle, that can't have been doing the internal bass driver any good. Not affected by volume setting, so output or PSU. Nothing really conclusive to be seen on a 'scope. When it was doing it, you could 'see' it virtually anywhere, including on the output stage power rails, which were bouncing around all over the place. It had a 'feel' of an intermittent output transistor about it. Nothing physical such as heat, cold or vibration would provoke it, so I initially rejected thoughts of bad joints. There are four output Tr's in it - 2 x PNP and 2 x NPN , paralleled up, so I removed one pair. No difference. Still worked perfectly well, and still had the random crackle. So I swapped the first two transistors back in. No change. Some time was then spent trying to prove where the noise was coming from, without any positive results, Eventually, I decided that it might actually be a bad joint. There was no indication that the board was built with lead-free solder, other than the fact that the joints were conical and dull.

I set about doing a blanket re-solder, and quickly ran into trouble. I don't know what on earth sort of solder they had used, but even on small joints, my temperature controlled bench iron was struggling. I even wound it up full to 450 deg, and it still wasn't good. On larger joints like the smoothing caps and the very chunky rectifier diodes, it wasn't having any of it at all. Eventually, I had to dig out my 45 year old 140 watt Weller gun. At least that made short work of reflowing the joints, but of course, you've got to then be twice as careful about running joints into one another, as the tip is really too big for this sort of job.

In the end, when it was all back together, it was silent, so I have to conclude that it *was* a bad joint. But what makes it so frustrating from a commercial 'let's make some money from this repair' point of view, is that unlike conventional leaded solder joints when they go bad, you just can't provoke lead-free bad joints to show themselves by any of the time-tested and trusted methods.

I hate the stuff with a passion >:-(

Arfa

Reply to
Arfa Daily
Loading thread data ...

This is one issue I won't disagree with you on. We're just seeing the beginning of serious servicing problems.

Reply to
William Sommerwerck

Anyway,

driver

it

vibration

are

actually

dull.

don't

full

a

Is one of your inducers an engraving tool with an insert of a nylon bolt with "sharpened" end/tip? to pcb only , no direct contact to any SMD of course as likely to flip them off. Unfortunately you have to monitor the o/p with phones because of the noise of the engraver. So what sort of solder do you think it was ? high Cu and tin ? at those sorts of temp very high probability of temp induced Si failures. Manufacture date?

Reply to
N_Cook

ObAOL: Me too! In the last few weeks alone I repaired several custom A/D converter boards where they were inoperative until you put a slight pressure a 44 pin PLCC dual port ram chip located between the micro and the PLD. Looking at all the pins under a stereo microscope which has 25x magnification revealed no bad solder joints, every joint looked flawless. Yet when I resoldered the chip (with leaded solder) the boards worked perfectly. I'd like to round up the folks who started this nonsense and drop 'em in a large vat of molten no-lead solder, which is about the only thing it'd be good for.

On the plus side, I have not yet seen any failures that could be attributed to whisker growth.

Reply to
JW

Hi N_cook,

Have you ever noticed that your quoting is broken? If you're interested in fixing it, check this web page:

formatting link

Reply to
JW

I tend to use a Biro pen, a hot air rework station (turned down to 100 deg or so), a can of freezer, and the butt end of a bloody great screwdy. Oh yes. And a lump hammer ... :-)

Seriously though, with normal leaded joints, I've never found it necessary to use anything other than 'gentle' methods to pin a bad joint down to within a square cm of board, which is what makes lead-free joint problems so incredibly frustrating. I get them all the time where you've only got to look sideways at the board, and the joint will go bad, and yet no amount of provocation will bring it on when it's right, nor get it back when it's wrong. And when you do eventually find it, the component is often hanging out of the board - except you can't actually see that it is until you tug on it, or come to re-solder it, when the solder flies away from the component leg to form a ring on the pad, leaving the leg looking as though it's never been soldered in its life ... And how many times do these lead-free bad joint jobs bounce a couple of weeks later ? Can you imagine the implications if the rotten stuff ever does find its way into avionics and other life-preserving areas ? New programme on Discovery ? "Aircrash Investigation - The Lead-Free Years" ?

As to the Quad. It was from their "Lite" series. The owner's user guide says "03 - 05 Issue 1" inside its front cover so I'm guessing maybe 2005 ?? which is before the 'official' lead-free introduction cut off point of June 2006, but a number of manufacturers - notably Sony for instance - were manufacturing with the stuff well in advance of that date. There is also a note in the back cover about EC compliance requirements that it conforms to, but they are about EMC and voltage safety. No mention of lead-free.

I suppose it's possible that the thing was not built with lead-free, but it certainly looked and behaved like the stuff. Which brings us back to a point often made by Mr Cook. How do you tell for sure when the board isn't categorically marked ?

I really don't know what alloy had been used on this. Only that it had trouble melting on the end of my normal continuous-use temperature-controlled bench iron, even when set at max. It did melt ok with the 140 watt Weller gun on it, but even with that, it only 'flowed' fairly normally. Anyone who has ever used one of these beasts, will know that under normal circumstances, a small joint will be pretty much boiled on the tip ...

Arfa

Reply to
Arfa Daily

Anyway,

driver SMD desoldering tweezers

For simple 2 land devices like Rs and Cs , apply the tweezers across the long axis or short axis? flat good metal/metal contacts generally shortwise but full-on solder contact lengthwise although spherical/flat contacts until initial solder melt.

really

it

vibration

are

removed

change.

actually

dull.

don't

joints,

full

a

that

have you tried cut finger-nail clipping test - oh no a reason to save nail clippings. Sometimes running a point-ended clipping along the run of PLCC pins , the "note" will change with poor soldered pins compared to the rest

Reply to
N_Cook

so

of

on

never

implications

says

which

2006,

to,

it

point

with

under

I wonder if there is a "one-time" formulation of solder, low temp initial use, then higher temp if reworked, or some sort of chemical de-eutectic process over time.

The earliest PbF i've found was 2001 Yamaha unit

Reply to
N_Cook

No I haven't heard *that* one yet. What will people say at work when they see a dish full of clippings? :) Perhaps a plastic probe of some sort might also work...

Reply to
JW

On 8 feb, 13:50, "Arfa Daily" wrote: (...)>

I agree. I just repaired the control card of my room air conditioner. The PCB was marked as ROHS. The failure was that the swing motor wasn =B4t working properly. It would work sometimes, and sometimes not, until it didn=B4t turned on no matter what. Testing the motor for continuity revealed that the internal wiring was ok, so the problem was in the control card. Testing of the relay which turns on/off the motor showed nothing relevant, prodding the relay showed nothing too and to the naked eye the relay looked like it was well soldered to the board without signs of arcing. Nonetheless I decided to remove the relay and solder it back... and problem solved :-/

I don=B4t know for sure what happens to lead free solder joints over time, but seems to me that over time the solder joint becomes some sort of insulator, even if it seems OK both physically and mechanically.

FWIW, a swing motor just consumes 4W at 220 VAC. It=B4s almost equal in power and size as a turntable motor for a microwave oven.

Reply to
lsmartino

... And how many times do these lead-free bad

implications

From an electronics engineer within an exempted industry, noy just allowed to use leaded solder but contractually must use tradional materials in there entirety. His company does not automatically believe documentation that comes with components specified as being non-RoHS. They test whether the tinning is 100 percent tin or traditional and not rely on fraudulent/erroneous paperwork. The implication is that other exempted end-users would not be so stringent

Reply to
N_Cook

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.