MAc 500s + Mac 600s- the PAT testing of...

[SoLiEn]

ok, its dark time again, how do I pat test these things safely? its a lot of money of light to screw up

 

thanks in advance!

 

Dan

[timmeh]

Test it as you would a normal appliance.

 

The hard part is getting the earth lead properly grounded.

[live]

Hi Dan

An easy way to ground it is to remove the base plates (couple of screws) slide the plate out and just next to the transformer there is a chassis ground

g

[SoLiEn]

any tests to avoid? on the pat tester we got some preset functions, i.e. lantern/appliance and cable?

[Pete McCrea]

I was under the impression that PAT Testing should be non invasive (after the checking of the fuse- except there generally). Therefore taking the cover off to conduct the test sort of nullifies the point in the test?

[live]

I was under the impression that PAT Testing should be non invasive (after the checking of the fuse- except there generally). Therefore taking the cover off to conduct the test sort of nullifies the point in the test?

 

 

Correct but this is the same chassis earth that the omega clamps couple with.I should have replied "In the abscence of clamps fitted etc" :)

[timmeh]

I was under the impression that PAT Testing should be non invasive (after the checking of the fuse- except there generally). Therefore taking the cover off to conduct the test sort of nullifies the point in the test?

 

Hi

 

True but in the case of a painted metal chassis (like all the 1st-gen Macs) you have to find an earth point, and that'll usually be inside the case (I tend to use the PSU transformer's mounting points as an earth.)

 

The alternative is of course to fail the unit completely because you could not perform an earth leakage test.

 

All the best

Timmeh

[Brian]

I was under the impression that PAT Testing should be non invasive (after the checking of the fuse- except there generally). Therefore taking the cover off to conduct the test sort of nullifies the point in the test?

Absolutely. Earth Continuity testing should be between the earth pin of the supply cord and accessible earthed metal parts. Taking the cover off is not an option.

[timmeh]

Absolutely. Earth Continuity testing should be between the earth pin of the supply cord and accessible earthed metal parts. Taking the cover off is not an option.

 

 

Hi

 

So with something like a MAC500 with no exposed bare metal (unless you remove a load of paint) where the resistance between metal parts and earth is infinite, would that constitute a PAT fail? Or could you consider that unit double insulated and therefore safe?

 

You wouldn't try to measure continuity between chassis earth and a piece of plastic, is there any difference here?

 

All the best

Timmeh

[Pete McCrea]

One option I've seen used, and is not necessarily correct, is to use a screw driver tip to act as a probe and allow contact to be made to exposed metal where the 1/4 connectors mount onto the unit. Another is to use the jaws on the test clip to remove paint on a screw to enable the reading to be taken.

 

As said before, this is not necessarily correct, but something I have seen used to prevent having to remove covers, and therefore make the whole test pointless.

[Brian]

One option I've seen used, and is not necessarily correct, is to use a screw driver tip to act as a probe...

Or use the probe supplied with the PAT tester :D

[grizzly]

Or use the probe supplied with the PAT tester :D

 

Not all PAT testers have a probe that can be used in this fashion for the earth bond test, but rather a lead with a fixed croc clip on the end. Hence the need to put a screwdriver in the jaws of the croc clip, to act as a temporary probe.

[maeterlinck]

Remember a large part of PATing is the visual inspection part of things. The scientific part is important, but might not show up a loose connection for instance. So opening up the base and checking all is good in there is no bad thing, but there would be very little point in taking an earth reference from there.

It's why servicing at the same time as PATing is such a good idea.

[grizzly]

Remember a large part of PATing is the visual inspection part of things. The scientific part is important, but might not show up a loose connection for instance. So opening up the base and checking all is good in there is no bad thing, but there would be very little point in taking an earth reference from there.

It's why servicing at the same time as PATing is such a good idea.

 

Indeed.

In fact, the ABTT CoP says (section 3.3, page 12):

Inspection should include, where possible, removing plug tops and appliance covers as necessary to examine vulnerable parts.

 

although no mention is made of taking off appliance covers, AFAICS, in the IEE CoP.