PAT testing damage (UK)

PAT?

-- Cheers, WB .............

Regulator might be toast. Or, you might be measuring a fairly high ripple current because none of the capacitors are working. Measure it with an oscilloscope to be sure.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Portable Appliance Test

-- Jeff Liebermann snipped-for-privacy@cruzio.com

150 Felker St #D Santa Cruz CA 95060 Skype: JeffLiebermann AE6KS 831-336-2558

Should really be PA Test, but nobody would be able to pronounce it.

A bit like PIN number. (IS there a name for these misnamed things?)

Gareth.

Yes. See:

Note that we don't have PAT testers in the USA. As part of our governments War on Industry, we trust the outsourced manufacturures in China to produce consumer appliances that electrocute only a modest number of users. We also enjoy the protection of a litigatory environment, that inspires massive recalls if one defective appliance is found on the theory that if one is defective, then the entire production run is also likely to be defective. We also have various testing and certification labs, that will guarantee that an appliance design will not kill the user or initiate a fire, even if the appliance doesn't work. With these protections in place, there's no need for PAT testing.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Well that's just great, Jeff!

In the UK we expect cheap crap to break, and to subsequently kill people. The fact that it never really has doesn't stop our enthusiasm for Health And Safety in spades.

Thanks for the RAS syndrome link. I've always chuckled at the naming of the programming language GNU, the acronym for "GNU's Not Unix".

Gareth.

"Jeff Liebermann is a Clueless Idiot "

** Shame on you.

** Got NOTHING to do with PAT testing !!!

PAT testing is all about the possibility that electrical equipment may become unsafe after a period of use, due to wear and tear, accidental damage and water ingress.

It is only *required* to be done were equipment is of a portable kind and provided for staff and others to use in a work environment.

For example, hire businesses have to regularly PAT test any electrical items they rent to folk.

It's an idea dreamt up by bureaucrats - and rather pointless since electrical faults and damage occur at ANY time and PAT testing does nothing to prevent that.

.... Phil

goes

was

at

on?

Now if a numb-skull used the discrete IEC lead tester, flash-tester, instead of the more down-to-ground ;-) PAT tester then expect such damage

Over the years, I've seen a lot of items from schools and commercial premises that have odd microprocessor-y problems, and a recent PAT sticker on them, so I'm certain in my own mind, that these have suffered damage as a result of either inept or inappropriate use of a tester. The items in question, are often boom boxes that are double insulated, and have a removable figure 8 power lead, so there is absolutely no point in applying these tests, anyway. As to wall-wart powered stuff, I can't recall ever seeing an item that may have been damaged in such a way, but if other items with a similar small power transformer fixed internally can suffer, I don't see why it shouldn't also be the case for an externally powered device. I think, however, with the bulging caps you say you've found, in this case it's probably either a wrong power supply having been used, or just general failure, rather than a PAT issue. Is it from a school ? If it is, it's probably either left on all the time, or subject to dopey kids and teachers digging it out of a cupboard in the music room, and jamming in the first power connector that fits, and appears to make it work ...

Arfa

Thanks Arfa, I was hoping for some real world experience.

This units power supply also has a 2 core mains lead, the 13A plug having a proper metal pin, so could be mistaken for an earthed unit re: PAT testing. It is not from a school.

I'm not sure what happens with "inappropriate" PAT testing, hence this post. I was wondering if a high voltage was able to break through or induced to the secondary winding to zap the unit in question if it was plugged in and turned on.

As for the bulging caps, it would surely take some power to do this, which I guess could not come from a PAT tester, though if they were zapped by one, subsequent use of the unit with its own power supply may cause further damage?

As per my post, I suspect, like you, this was a "wrong PSU used numpty error", though any info on the hazards of PAT testing is welcome.

Cheers,

Gareth.

"Gareth Magennis"

**Another, bloody pathetic, WOFT troll.

.... Phil

What a charming man.

OK, I have looked a little deeper into this problem now with a schematic, and it seems that all the electro caps on both sides of the 3 main regulator circuits are bursting, as are a few smaller ones dotted about the PCB. Unless a PAT tester can somehow damage all these caps downline of the regulators, without blowing the regulators, I now suspect this to be a bad batch of electrolytics.

The 4.1 volts I measured at the 3.3v regulator is, as Jeff suggested, due to ten tons of ripple and HF hash. Replacing the 3 on the 3.3v regulator restores it to 3.3v with a bit of ripple, so this reg is probably OK.

The caps are green Jamicon 105degree types. All 220uF 16v ones have blown, as have a few 100uF 16v of the same type. All the 10uF 16v ones dotted about look OK.

What fun.

Gareth.

Possibly. In general, wall warts are class II items with no earth pin so visual inspection is all I would do. In the (unlikely) event that it was a Class I device with earth pin and exposed metalwork then a voltage test would be made between line and the metalwork and a resistance check from metal to earth pin. I would not test a wall wart with equipment (e.g. printer) connected as the equipment will be working on low voltage and not be subject to testing. I doubt that a short pulse of high voltage would cause caps to bulge anyway.

It wasn't my decision. We have the best government and regulatory agencies that money can buy.

Not even a little bit?

That's not a problem in the USA. We have the worlds best throw away society. Our tools and electrical equipment are never allowed to get old enough to become dangerous. No self respecting government employee would even consider using a used tool or machine. At the first sign of wear or damage, the device is immediately thrown away, err... recycled, and replaced with a brand new Chinese replacement. This may also explain why the USA is nearly bankrupt.

In the USA, workers and staff are largely expendable. In some cases, the tools and equipment are worth more than the operator. I don't see much reason for an expensive PAT tester, when simply replacing the operator will probably be cheaper.

Yeah, that makes sense. The tools and equipment that isn't recycled or stolen, usually ends up at the local rental yards. I recently had to rent a chain saw with a big 36" bar. While not electrical, it would not have passed even a cursory safety inspection. Instead of mandating PAT testing, perhaps it might be better to give the money back to the businesses so they can afford to buy new equipment?

But, if it saves one life, it must obviously be worth the cost and effort. That's also the logic here in the USA, particularly in the drug and product liability industry. If there's only one victim among millions of perfectly safe users, that's sufficient grounds for extorting substantial sums from the vendors and enriching the legal establishment. The search for victims has even extended to TV advertising by law firms.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Just a minor note... It takes some time for bulging caps to develop. It's unlikely that there's enough energy in a wall wart to destroy the caps during a PAT test. It's also not over voltage that kills the caps. It's the ripple current through the cap that causes the heating. A cap, with a fixed DC voltage applied, will not blow (unless the dielectric is perforated). More likely, the caps were defective and blown for many months prior to the PAT test.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

We know

--
Live Fast Die Young, Leave A Pretty Corpse

On Wed, 27 Jul 2011 18:36:27 +0100, "Gareth Magennis" put finger to keyboard and composed:

If you can read the flash memory, then checksum its contents. You could also inspect the contents for misspelt text strings.

Another thing to try is to lift the chip's clock pin (serial flash), or its CS or OE pin (parallel flash). If the machine's symptoms remain the same, then it's a good bet that the flash is bad, or its supply has too much ripple.

If the regulator is linear, then I'd say it is faulty. Otherwise, if it is a switchmode type, then it could be a capacitor issue.

- Franc Zabkar

--
Please remove one 'i' from my address when replying by email.

He was raised by dingoes.

Then he ate them. Alive they were, as he chewed on them!

--
It's easy to think outside the box, when you have a cutting torch.