Will my TSE zap my children?

[Alan Hope]

Noob question. Before trying checkout again I went over all the earthing etc, and prodded around the amp with a continuity tester.

Slightly disconcerted to find that both high-voltage live leads from the transformer are in continuity with ground. Looking at the circuit diagram, this is presumably because the centre-tap is grounded causing the continuity, however the high voltage will not actually flow to ground.

Yes?

[Alan Hope]

OK, did some googling and some learning. Balanced power supplies. I'm happier now ...
Balanced Power from Equi=Tech

[kevinkr]

Since the center tap is on the secondary side of the transformer there is no problem - no connection to the mains is present.. The key is to make sure that the metal parts of the chassis are safely earth grounded, and the unit is properly fused. (Place the fuse before the power switch!)

I think the thread title needs to be changed. I doubt George would be too thrilled.

[kevinkr]

Thread title edited..

[Alan Hope]

Originally Posted by kevinkr

Since the center tap is on the secondary side of the transformer there is no problem - no connection to the mains is present.. The key is to make sure that the metal parts of the chassis are safely earth grounded, and the unit is properly fused. (Place the fuse before the power switch!)

I think the thread title needs to be changed. I doubt George would be too thrilled.

Guess it was a bit dramatic. Thanks for the reassurance, guys. I see George touches on the subject in his safety pages:

Equipment Grounding

Will have another go at the checkout procedure next few days!

[stratus46]

Originally Posted by Alan Hope

OK, did some googling and some learning. Balanced power supplies. I'm happier now ...
Balanced Power from Equi=Tech

New technology? It's been done in Hollywood for decades. The main reason it's needed is for the AC line filters that treat the power as balanced line (it isn't) and tie .001 capacitors from line to ground and neutral to ground. The problem is (in North America) ground and neutral are the SAME potential so you only get current from line to ground. Install several hundred units and you get some serious loop currents- HUM. The proper solution would be to get rid of the filters but it's cheaper to put in balanced AC.

G²

[tubelab.com]

Will the TSE harm my children, pets, or spouse? Will a toaster, TV set, or any other device that is plugged into the wall outlet do the same? The answer to both questions is the same. The TSE is designed such that it is completely safe as long as ALL INTERNAL COMPONENTS are not accessible by the user and ALL CONDUCTIVE SURFACES that ARE accessible by the user are GROUNDED.

It is the RESPONSIBILITY of the builder to assure that these conditions are met before plugging the amp into the wall outlet. If the amp is assembled properly...your children are safe....from electricity. The TSE and any other tube amp contains tubes, and they get HOT, hot enough to burn skin. The amp should still be placed out of reach of little hands that are curious.

It should also be noted that should a tube become broken, the exposed metal pieces can carry lethal voltages. This is true of any tube amp.

[Alan Hope]

Originally Posted by tubelab.com

Will the TSE harm my children, pets, or spouse? Will a toaster, TV set, or any other device that is plugged into the wall outlet do the same? The answer to both questions is the same. The TSE is designed such that it is completely safe as long as ALL INTERNAL COMPONENTS are not accessible by the user and ALL CONDUCTIVE SURFACES that ARE accessible by the user are GROUNDED.

It is the RESPONSIBILITY of the builder to assure that these conditions are met before plugging the amp into the wall outlet. If the amp is assembled properly...your children are safe....from electricity. The TSE and any other tube amp contains tubes, and they get HOT, hot enough to burn skin. The amp should still be placed out of reach of little hands that are curious.

It should also be noted that should a tube become broken, the exposed metal pieces can carry lethal voltages. This is true of any tube amp.

Absolutely! As a young teenager I stuck my fingers into a live light switch socket - an unforgettable experience. As a doctor, electrocution is one of the things we learn, and it is a testament to general electrical safety that I have seen so few cases. Here in the UK our mains is 50hz - the most dangerous frequency in cardiac arrest terms (VF).

My original post was prompted by my own safety concerns - which turn out to have been misplaced, and simply revealed my own lack of knowledge. I am acutely aware that I am not that experienced at this. Yeah, there is a fuse in the mains plug which did not blow which should have told me something in this particular case. To make things clear, I was not implying anything inherently unsafe about the TSE.

I suspect there are others here at a similar level of knowledge to me, ie building and learning at the same time. While Google goes a long way - this forum is a friendly and reassuring project-specific resource. Thanks!

I have a load of cheap multimeters to allow me to checkout using George's step-by-step procedure, which is reassuringly safety-orientated.

Happy New Year everybody!

[Nikon1975]

The tester I have at work for safety compliance check that a maximum resistance of 0.5 ohm is present between the chassis (all the parts) and the earth. This is an easy test to do with an ohm meter.

I have the same problem, but my child is two, so is very unpredictable what he can do. I tend not to use tube amps when he is around, and I wanted to make a tube cover for the tubes, so he cannot stick his fingers on them.

Additionally, he has spirit of emulation toward me, and he like to stick screwdrivers and random objects in the air inlets. I guess he try to "mod". :-)

D.

[dhaen]

Most of the valve/tube DIY builds seen on these pages would not comply to national safety standards.
That's not to say that are outright dangerous - indeed my own amp would not comply due to hot surfaces and the consequences of valve breakage.
A valve amp that fully complies would be a dull beast with a large cage over the valves.
Better is to take reasonable steps and then put the amp out of reach of persons who may come to harm.

Earth testing with a multimeter alone is futile. You need to pass some amps between the chassis and mains earth to make sure that the impedance is low and that the path can take a fault current. Remember instantaneous fault current can be many time the fuse rating.
This is one of the tests that can carried out with a UK "Portable Appliance Tester". Try to find a "tame" electrician who will run the test for you