Help - Amp has failed a PAT test

ICBM

ecc83 said:

It is my understanding that modern gear at least must have the incoming mains earth connected as the sole wire to its own earth bolt and not any handy fixing used for say a transformer where the earth connection might be forgotten if the transformer was changed?

Yes, that’s correct.

martinw

ICBM said:

Same here. Actually the very first thing I do is to open the mains plug, if it’s not a moulded one. You are probably quite familiar with the things I often find too!

Sorry, I read my last post back and it reads as if it was aimed at you . Not meant at all - but I’ve come across quite a few things with currently-valid PAT stickers on where I doubt the tester did any more than check the earth continuity.

No worries

jpfamps

Modulus_Amps said:

has anybody ever had a PAT test fail on "proper" equipment, excluding dodgy plug wiring

Yes I have.

For example a Yamaha PA where there powder coat had not been scrapped of the chassis to make a good ground connection.

jpfamps

ecc83 said:

It is my understanding that modern gear at least must have the incoming mains earth connected as the sole wire to its own earth bolt and not any handy fixing used for say a transformer where the earth connection might be forgotten if the transformer was changed?

Dave.

There needs to be a dedicated bolt for earthing. You can attach other earth leads to this but not use the bolt for fixing parts to the chassis.

The earth tag must be crimped NOT just soldered. 

My understanding of the regs is that a self tapping screw is not acceptable. 

The best method is to use a bolt welded to the chassis, although few amps use this method.

RiftAmps

jpfamps said:

ecc83 said:

It is my understanding that modern gear at least must have the incoming mains earth connected as the sole wire to its own earth bolt and not any handy fixing used for say a transformer where the earth connection might be forgotten if the transformer was changed?

Dave.

There needs to be a dedicated bolt for earthing. You can attach other earth leads to this but not use the bolt for fixing parts to the chassis.

As far as I understand it @jpfamps , the safety-earth bond cannot have another function including connection of other earth leads. It needs to be a dedicated connection that has no other job, mechanical or electrical. I certainly wouldn't attach anything else to it, just in case your interpretation of the regs is incorrect.

You also need to ensure that the correct 12mm picture sticker is used, something that is rarely done.

maltingsaudio

jpfamps said:

Modulus_Amps said:

has anybody ever had a PAT test fail on "proper" equipment, excluding dodgy plug wiring

Yes I have.

For example a Yamaha PA where there powder coat had not been scrapped of the chassis to make a good ground connection.

Had a case where the powder coating was so good on the whole chassis that the only way to get the earth bond passed was to take the top off the amp and connect the black lead from the PAT machine to the earth lug to which the units earth was attached. 

jpfamps

RiftAmps said:

jpfamps said:

ecc83 said:

It is my understanding that modern gear at least must have the incoming mains earth connected as the sole wire to its own earth bolt and not any handy fixing used for say a transformer where the earth connection might be forgotten if the transformer was changed?

Dave.

There needs to be a dedicated bolt for earthing. You can attach other earth leads to this but not use the bolt for fixing parts to the chassis.

As far as I understand it @jpfamps , the safety-earth bond cannot have another function including connection of other earth leads. It needs to be a dedicated connection that has no other job, mechanical or electrical. I certainly wouldn't attach anything else to it, just in case your interpretation of the regs is incorrect.

You also need to ensure that the correct 12mm picture sticker is used, something that is rarely done.

I would never connect anything else to the safety earth ground (it would not be good practice in audio regardless of the regs; the audio should be grounded to a single point near the input), but my understanding of the old regs is that it is acceptable to bolt other earth connections on top of the safety ground.

I've certainly seen this approached used in kit that has been through approvals.

As I'm sure you know the regs are in the process of being updated, and I've not yet ploughed through the latest revision regarding earthing. 

jpfamps

maltingsaudio said:

jpfamps said:

Modulus_Amps said:

has anybody ever had a PAT test fail on "proper" equipment, excluding dodgy plug wiring

Yes I have.

For example a Yamaha PA where there powder coat had not been scrapped of the chassis to make a good ground connection.

Had a case where the powder coating was so good on the whole chassis that the only way to get the earth bond passed was to take the top off the amp and connect the black lead from the PAT machine to the earth lug to which the units earth was attached. 

I've had that issue too; can be a real pain.

normula1

Back in the day, I had a PAT tester doing the rounds on the computers at work. I had to let him down gently when he failed the earth bonding test on a specialist computer that had an entirely plastic case. We also had cases of things being blown up by the >1000 volt test they did too.

ecc83

normula1 said:

Back in the day, I had a PAT tester doing the rounds on the computers at work. I had to let him down gently when he failed the earth bonding test on a specialist computer that had an entirely plastic case. We also had cases of things being blown up by the <1000 volt test they did too.

Many, many years ago I did a one day course at Sharp Electronics to get my PAT tester's ticket (back in the day when retail electronics was a decent trade!) and we were made very aware that certain equipment was not to be zapped with 1000s of volts!

Dave.

maltingsaudio

Flash test no longer compulsory part of PAT test, then again PAT test not compulsory but that’s another can of worms!

ICBM

Just spotted this on Ebay...

https://www.ebay.co.uk/itm/Marshall-Lead-20-Combo-Amplifier-378/132431140486

Have a look at the pics of the back.

martinw

ICBM said:

Just spotted this on Ebay...

https://www.ebay.co.uk/itm/Marshall-Lead-20-Combo-Amplifier-378/132431140486

Have a look at the pics of the back.

Lol!

"All items have been tested". So that's ok then.