Maker Pro
Maker Pro

PAT testing. Anyone else think that sometimes, it causes damage ?

A

Arfa Daily

Jan 1, 1970
0
Following on from my post of a couple of days ago, looking for a schematic
set for a JVC with a dead radio section, not having found one, I had a
little search through my extensive stock of JVC manuals, and came up with
one for a similar(ish) model of the same vintage, which used the same radio
tuner sub-board.

Using this, I was able to determine that all rails were established and
correct, that the PLL chip was idling and unlocked, that the FM subsystem IC
was idling, and that the VFD for the radio section had the correct supplies
and drives, but was being 'muted' by the drive IC, which is also the system
control processor. No I2C data was being sent to the PLL IC, hence the
reason that it never ramped the tune voltage to the RF module. The I2C bus
was however, correctly active for other control functions, such as handling
the CD section. About the only conclusion that I could come to, was that
either the microcontroller was in some subtle way faulty or, more likely I
felt, its software was screwed.

Last week, we had a couple of claps of thunder locally, so I began to think
that this might be a 'storm damage' job. Either way, in view of its age, it
was not going to be a practical repair, so I informed the store that it came
to me from, and put it back together. It was at this point that I noticed
the PAT test label wrapped around its power lead, and this indicated that
the test had been carried out only a week or so before it became faulty. At
this point, I began wondering if the fact that it had had the tests
performed on it, probably by someone with an automatic tester and little
understanding of what it is doing, and where it is appropriate to run which
tests, had resulted in damage to the microcontroller. I have seen other
equipment on a number of occasions over the years, with similar 'odd'
failures, and sometimes power supply failures, shortly after being PAT
tested.

I've never been a great believer in the appropriateness of applying these
tests to double insulated and transformer based equipment, particularly
given that large DC spikes are applied, which with some testers are actually
twice the nominal line voltage. Given that in much microcontroller based
electronic equipment, digital grounds are not directly bonded to other
system grounds, it seems to me that having big voltage spikes flashing
around between the primary side of the power supply, and cabinet metalwork,
which is not grounded to any line power earth, but may well be AC common to
internal DC grounds via low puff ( and sometimes not-so-low ) caps and high
value resistors, is asking for trouble of the same nature as you might
expect from static damage, or pulse damage from nearby lightning strikes.

I would be interested in knowing if I'm on my own on this one, or if anybody
else involved professionally in service work - or indeed anyone who carries
out PAT testing - has any similar experience, or opinions on this.

Arfa
 
P

Phil Allison

Jan 1, 1970
0
"Arfa Daily"

re: JVC midi size hi-fi system.
I would be interested in knowing if I'm on my own on this one, or if
anybody else involved professionally in service work - or indeed anyone
who carries out PAT testing - has any similar experience, or opinions on
this.


** Why on earth would a unit like that have to be PAT tested ????

No requirement exists here in Australia for low risk items used in non
hazardous work environments to be regularly tested.




..... Phil
 
N

N_Cook

Jan 1, 1970
0
Arfa Daily said:
Following on from my post of a couple of days ago, looking for a schematic
set for a JVC with a dead radio section, not having found one, I had a
little search through my extensive stock of JVC manuals, and came up with
one for a similar(ish) model of the same vintage, which used the same radio
tuner sub-board.

Using this, I was able to determine that all rails were established and
correct, that the PLL chip was idling and unlocked, that the FM subsystem IC
was idling, and that the VFD for the radio section had the correct supplies
and drives, but was being 'muted' by the drive IC, which is also the system
control processor. No I2C data was being sent to the PLL IC, hence the
reason that it never ramped the tune voltage to the RF module. The I2C bus
was however, correctly active for other control functions, such as handling
the CD section. About the only conclusion that I could come to, was that
either the microcontroller was in some subtle way faulty or, more likely I
felt, its software was screwed.

Last week, we had a couple of claps of thunder locally, so I began to think
that this might be a 'storm damage' job. Either way, in view of its age, it
was not going to be a practical repair, so I informed the store that it came
to me from, and put it back together. It was at this point that I noticed
the PAT test label wrapped around its power lead, and this indicated that
the test had been carried out only a week or so before it became faulty. At
this point, I began wondering if the fact that it had had the tests
performed on it, probably by someone with an automatic tester and little
understanding of what it is doing, and where it is appropriate to run which
tests, had resulted in damage to the microcontroller. I have seen other
equipment on a number of occasions over the years, with similar 'odd'
failures, and sometimes power supply failures, shortly after being PAT
tested.

I've never been a great believer in the appropriateness of applying these
tests to double insulated and transformer based equipment, particularly
given that large DC spikes are applied, which with some testers are actually
twice the nominal line voltage. Given that in much microcontroller based
electronic equipment, digital grounds are not directly bonded to other
system grounds, it seems to me that having big voltage spikes flashing
around between the primary side of the power supply, and cabinet metalwork,
which is not grounded to any line power earth, but may well be AC common to
internal DC grounds via low puff ( and sometimes not-so-low ) caps and high
value resistors, is asking for trouble of the same nature as you might
expect from static damage, or pulse damage from nearby lightning strikes.

I would be interested in knowing if I'm on my own on this one, or if anybody
else involved professionally in service work - or indeed anyone who carries
out PAT testing - has any similar experience, or opinions on this.

Arfa

Now if it was actually a flash test not a pat test then who needs lightning.
 
A

Arfa Daily

Jan 1, 1970
0
Phil Allison said:
"Arfa Daily"

re: JVC midi size hi-fi system.



** Why on earth would a unit like that have to be PAT tested ????

No requirement exists here in Australia for low risk items used in non
hazardous work environments to be regularly tested.




.... Phil

Well, to some extent, this is my point. I'm no expert on the regs, and it's
my feeling that items such as this should not be subject to the high voltage
tests for the very reasons that I suspect that it may cause damage to them.
Possibly, they are not strictly speaking required to be tested, but several
of the places that I do work for, have local authority customers, so care
homes, schools, that sort of thing, and every item that I see from such
establishments - including fully plastic cased boom-boxes - always has a
"tested" sticker on it, with a date for the next test, so it's my belief
that a shotgun approach for every item that runs off the mains, and is not
bolted down, is being applied. And probably by the general maintenance man,
who just has an automatic tester as part of his kit box, and a general
mandate to use it ...

Arfa
 
A

Arfa Daily

Jan 1, 1970
0
Phil Allison said:
"Arfa Daily"

re: JVC midi size hi-fi system.



** Why on earth would a unit like that have to be PAT tested ????

No requirement exists here in Australia for low risk items used in non
hazardous work environments to be regularly tested.




.... Phil

Well, to some extent, this is my point. I'm no expert on the regs, and it's
my feeling that items such as this should not be subject to the high voltage
tests for the very reasons that I suspect that it may cause damage to them.
Possibly, they are not strictly speaking required to be tested, but several
of the places that I do work for, have local authority customers, so care
homes, schools, that sort of thing, and every item that I see from such
establishments - including fully plastic cased boom-boxes - always has a
"tested" sticker on it, with a date for the next test, so it's my belief
that a shotgun approach for every item that runs off the mains, and is not
bolted down, is being applied. And probably by the general maintenance man,
who just has an automatic tester as part of his kit box, and a general
mandate to use it ...

Arfa
 
A

Arfa Daily

Jan 1, 1970
0
N_Cook said:
Now if it was actually a flash test not a pat test then who needs
lightning.

Well, who's to say that it's not getting one of these as well ? If such
tests are being done by people who don't understand the implications ...

I would say that there is also potential for metal cased items such as this,
to get 'abused' by flash tests on metal boxed sockets as are often found in
local authority buildings, if the item remains plugged in. I could easily
see the metal case getting used as an 'earth' by someone who didn't realize
that it's not. As far as they are concerned, it's probably just a big lump
of metal plugged into the mains !

I might be completely wrong on all this. Just that over the years, I seem to
have seen a lot of 'odd' faults that finally seem to come down to faulty uP
chips, in items that carry a PAT test sticker with a very recent date on it.

Arfa
 
A

Adrian C

Jan 1, 1970
0
Last week, we had a couple of claps of thunder locally, so I began to
think that this might be a 'storm damage' job. Either way, in view of
its age, it was not going to be a practical repair, so I informed the
store that it came to me from, and put it back together. It was at this
point that I noticed the PAT test label wrapped around its power lead,
and this indicated that the test had been carried out only a week or so
before it became faulty. At this point, I began wondering if the fact
that it had had the tests performed on it, probably by someone with an
automatic tester and little understanding of what it is doing, and where
it is appropriate to run which tests, had resulted in damage to the
microcontroller. I have seen other equipment on a number of occasions
over the years, with similar 'odd' failures, and sometimes power supply
failures, shortly after being PAT tested.

Yup, PAT testing killed it, or correctly the incorrect procedure

This would have been Class II double insulated, so a tester would have a
choice of either a 'hard test' or 'soft test' to check the insulation
resistance, as part of the test.

The 'hard test' is a measurement of resistance (over 2Mohm ClassII)
found using a test voltage of 500V DC applied between 1) L&N connected
AND 2) any exposed possibly conductive surfaces (wandering probe)

The 'soft test' is powering the thing up normally on supply, and using a
wandering probe to measure any leakage current fron exposed possibly
conductive surfaces.

A 'hard test' is the thing for non-electronic equipment, 'soft' for
everything else. However, the wizzy do-everything electronic testers
make selecting soft and hard tests as easy as clicking a button, and
mistakes can and do happen.

I trained (C&G 2377) in doing this as a possible part/full time job, but
the risks of blowing up perfectly OK equipment, plus the meagre earnings
doing hundreds of items in an office, made me abandon the idea quite
quickly.
 
A

Arfa Daily

Jan 1, 1970
0
Adrian C said:
Yup, PAT testing killed it, or correctly the incorrect procedure

This would have been Class II double insulated, so a tester would have a
choice of either a 'hard test' or 'soft test' to check the insulation
resistance, as part of the test.

The 'hard test' is a measurement of resistance (over 2Mohm ClassII) found
using a test voltage of 500V DC applied between 1) L&N connected AND 2)
any exposed possibly conductive surfaces (wandering probe)

The 'soft test' is powering the thing up normally on supply, and using a
wandering probe to measure any leakage current fron exposed possibly
conductive surfaces.

A 'hard test' is the thing for non-electronic equipment, 'soft' for
everything else. However, the wizzy do-everything electronic testers make
selecting soft and hard tests as easy as clicking a button, and mistakes
can and do happen.

I trained (C&G 2377) in doing this as a possible part/full time job, but
the risks of blowing up perfectly OK equipment, plus the meagre earnings
doing hundreds of items in an office, made me abandon the idea quite
quickly.

OK Adrian. That's just the sort of detailed and informed input that I was
looking for, and backs my feelings on the matter. I think I might mention
this to the shop who took this item in, when I return it tomorrow.

Arfa
 
N

N_Cook

Jan 1, 1970
0
Adrian C said:
Yup, PAT testing killed it, or correctly the incorrect procedure

This would have been Class II double insulated, so a tester would have a
choice of either a 'hard test' or 'soft test' to check the insulation
resistance, as part of the test.

The 'hard test' is a measurement of resistance (over 2Mohm ClassII)
found using a test voltage of 500V DC applied between 1) L&N connected
AND 2) any exposed possibly conductive surfaces (wandering probe)

The 'soft test' is powering the thing up normally on supply, and using a
wandering probe to measure any leakage current fron exposed possibly
conductive surfaces.

A 'hard test' is the thing for non-electronic equipment, 'soft' for
everything else. However, the wizzy do-everything electronic testers
make selecting soft and hard tests as easy as clicking a button, and
mistakes can and do happen.

I trained (C&G 2377) in doing this as a possible part/full time job, but
the risks of blowing up perfectly OK equipment, plus the meagre earnings
doing hundreds of items in an office, made me abandon the idea quite
quickly.


What about 5KV or 10KV flash testers being used in the wrong situations?
 
A

Adrian C

Jan 1, 1970
0
Every mains powered electrical item has to be if used in the work place,
etc. However, the procedure isn't the same for everything.

Nope. It's 5 Years in an "Environment where the equipment or supply cord
is NOT subject to flexing in normal use and is NOT open to abuse and is
NOT in a hostile environment"

Australia PAT testing (they call it 'test and tag') does looks fairly
similar, if not the same to the UK.

For example, within Victoria the Occupation Health & Safety Act 2004
states:
“An employer must, so far as reasonably practicable, provide and
maintain for employees of the employer a working environment that is
safe and without risk to health.”

Exact same statement is in the UK H&S Act (probably no surprise there -
we probably wrote it on paper first... ;-)

The standard AS/NZS 3760 is referred as a way of implementing this.

Here is the testing interval from that standard.

http://policies.swinburne.edu.au/ppdonline/showdoc.aspx?recnum=TEM/2009/7

In the UK however, we have a document published by the IET called "Code
of Practice for In-Service Inspection and testing of electrical
equipment" that recommends the following PAT testing schedule.

It is a bit different ...

http://www.linpat.co.uk/Suggested Frequency of Testing.htm

Australia ain't the world...

He doesn't live in the world ...
 
A

Adrian C

Jan 1, 1970
0
Nope. It's 5 Years in an "Environment where the equipment or supply cord
is NOT subject to flexing in normal use and is NOT open to abuse and is
NOT in a hostile environment"

Sorry, that was aimed at the troll ...
 
A

Adrian C

Jan 1, 1970
0
What about 5KV or 10KV flash testers being used in the wrong situations?

Flash testing (AKA Dielectric Strength testing / Hi-POT testing) is done
by manufacturers as part of their 'out the door' production checks.

The IET code recommends NOT doing this as part of a user testing
programme, for guidence will be required from the manufacturer for
precautions applying the test AND the flash testing itself may encorage
after failure of the insulation.
 
A

Arfa Daily

Jan 1, 1970
0
Mark Allread said:
Arfa Daily wrote:

(some content snipped)

I had to look up "PAT Testing" online. It sounds like yet one more
unnecessary time-and-money-wasting government annoyance, like lead-free
solder and banned cleaning solvents. I'm sure we in the USA will be doing
that too, soon enough. At first glance, an incorrectly applied PAT sounds
like a fine way to destroy MOV protection devices.

Yep, I'm sure that where we've been, you boys in the U.S. won't be far
behind, although in the case of such things as health and safety, the green
mist, the supposed hazards of lead, and belief in the dogma of global
warming (with the possible exception of Al Gore), you seem to maintain a
proud and dogged resistance to being dragged in. I wish that the people and
powers of Europe in general, and the UK in particular, had a similar point
of view ... :-(

Arfa
 
P

Phil Allison

Jan 1, 1970
0
"Adrian C"
Phil Allison

Nope. It's 5 Years in an "Environment where the equipment or supply cord
is NOT subject to flexing in normal use and is NOT open to abuse and is
NOT in a hostile environment"

Australia PAT testing (they call it 'test and tag') does looks fairly
similar, if not the same to the UK.


** This guide from WorkCover NSW makes it CLEAR that there is NO testing
needed in this example.

http://www.workcover.nsw.gov.au/for...testing_tagging_electrical_equipment_1336.pdf

See item 7: " How often should I 'test and tag' my electrical equipment. "

" For all other workplaces, the inspection and testing intervals are
described in the standard, AS/NZS 3760 but ONLY need be applied to
electrical equipment that has been assessed as operating in a hostile
operating environment as described in clause 64 of the OHS Regulation."

BTW:

The issue here is PAT testing, I have no argument that regular visual
inspections for damage or deterioration etc are needed under the OHS laws
here.


..... Phil
 
P

Phil Allison

Jan 1, 1970
0
"Mark Allread"
I had to look up "PAT Testing" online. It sounds like yet one more
unnecessary time-and-money-wasting government annoyance, like lead-free
solder and banned cleaning solvents. I'm sure we in the USA will be doing
that too, soon enough. At first glance, an incorrectly applied PAT sounds
like a fine way to destroy MOV protection devices.


** MOVs are NOT connected from line to ground inside equipment sold in
Europe or Australia - cos it is a very dangerous practice.

In any case, the appliance tester only outputs a very small current to the
device under test in order to measure leakage to frame or chassis and is not
normally applied across the AC line terminals.


..... Phil
 
A

Arfa Daily

Jan 1, 1970
0
Phil Allison said:
"Adrian C"


** This guide from WorkCover NSW makes it CLEAR that there is NO testing
needed in this example.

http://www.workcover.nsw.gov.au/for...testing_tagging_electrical_equipment_1336.pdf

See item 7: " How often should I 'test and tag' my electrical equipment.
"

" For all other workplaces, the inspection and testing intervals are
described in the standard, AS/NZS 3760 but ONLY need be applied to
electrical equipment that has been assessed as operating in a hostile
operating environment as described in clause 64 of the OHS Regulation."

BTW:

The issue here is PAT testing, I have no argument that regular visual
inspections for damage or deterioration etc are needed under the OHS laws
here.


.... Phil

Agreed

Arfa
 
T

Tim Schwartz

Jan 1, 1970
0
Well, to some extent, this is my point. I'm no expert on the regs, and
it's my feeling that items such as this should not be subject to the
high voltage tests for the very reasons that I suspect that it may cause
damage to them. Possibly, they are not strictly speaking required to be
tested, but several of the places that I do work for, have local
authority customers, so care homes, schools, that sort of thing, and
every item that I see from such establishments - including fully plastic
cased boom-boxes - always has a "tested" sticker on it, with a date for
the next test, so it's my belief that a shotgun approach for every item
that runs off the mains, and is not bolted down, is being applied. And
probably by the general maintenance man, who just has an automatic
tester as part of his kit box, and a general mandate to use it ...

Arfa

Hello,

As someone in the USA who has no idea of what you are speaking of,
could you enlighten me as to what a PAT (particularly annoying
test?)test is? Is it required of consumer goods?

Regards,
Tim Schwartz
Bristol Electronics
 
A

Adrian C

Jan 1, 1970
0
** This guide from WorkCover NSW makes it CLEAR that there is NO testing
needed in this example.

http://www.workcover.nsw.gov.au/for...testing_tagging_electrical_equipment_1336.pdf

See item 7: " How often should I 'test and tag' my electrical equipment. "

" For all other workplaces, the inspection and testing intervals are
described in the standard, AS/NZS 3760 but ONLY need be applied to
electrical equipment that has been assessed as operating in a hostile
operating environment as described in clause 64 of the OHS Regulation."

OK, accepted. Didn't know about that 'code of practice' document.
 
C

Cydrome Leader

Jan 1, 1970
0
Michael A. Terrell said:
It's time for the European pheasants to gather pitchforks and burning
torches, for an all out assult on Brussels. Don't bother to pack a

brussels already looks burned down. bring wrecking balls and bulldozers
and just till that place back into the ground.
 
Top