Widowmaker Amps & Isolation Transformers

[nosaj]

I haven't been a bench tech in over a decade, but (I think) I've mentioned this before. For many years on the bench the State of CA required me to perform an AC leakage test on every piece I worked on with an AC plug on it. It had to be less than 25ua and I had to sign and date a sticker on each unit. I always thought it was a bit of a scam since the shop charged a $2 "fee" to do it. I don't think it was really enforced much. But with a shop doing $2m+ in repairs a year, those fees added up to serious money. Sencore had a bench variac with the probe and meter built in. We had one on every bench.

My B&K has one also.
Though I've never used it.

nosaj

[The Dude]

......Hospitals were the first place the need for grounded outlets was seen. Without a ground, any connection to a patient could electrocute the patient, especially when two or more machines were connected.

I was here for a vasectomy. Why are my arms black?

[Enzo]

Sencore used to market that. They would tell you to charge $10 per repair to check for leakage, and the unit "Will pay for itself in no time". That was their rationale for their MUCH higher prices than competing equipment.

[loudthud]

I'm not sure what year it was but the guys at UL started using a little "finger" probe to test products to make sure none of accessible metal parts were a shock hazard.

[R.G.]

I was here for a vasectomy. Why are my arms black?

Your arms? You're lucky. The guy just before you...

I'm not sure what year it was but the guys at UL started using a little "finger" probe to test products to make sure none of accessible metal parts were a shock hazard.

Yeah - the finger probe. It's about 9" long, tapers to a point like a kid's little finger and has several joints. I know of one amp that was failed on a early part of their safety certification run (silly people - actually following the rules and getting certified. I mean - how silly is that) because the grill was open enough that the finger could penetrate it, poke through the speaker cone, and touch hot power tubes at the back of the speaker.

[nickb]

Your arms? You're lucky. The guy just before you...


Yeah - the finger probe. It's about 9" long, tapers to a point like a kid's little finger and has several joints. I know of one amp that was failed on a early part of their safety certification run (silly people - actually following the rules and getting certified. I mean - how silly is that) because the grill was open enough that the finger could penetrate it, poke through the speaker cone, and touch hot power tubes at the back of the speaker.

If only there weren't so many kids with 9in long fingers....

[Enzo]

PArt of my career was spent in the coin op amusements field, and we all had huge key rings. One day one of the guys was with his kids, and the little guy, maybe 2 years old, was playing with dad's key ring. He wandered out of the room and a few minutes later, comes running in, "Daddy, daddy, keys made me owie." So we went in the other room, and there hanging from a wall outlet was the key ring. He had plugged one of the keys into the hot slot, and there was a big burn mark where one of the other keys had brushed the center screw on the plate.

never take safety for granted.

[Dave H]

If only there weren't so many kids with 9in long fingers...

They come in different sizes for different age children

[R.G.]

Here's a sobering example in favor of three-wire cords and isolation transformers that I just saw. It's not guitar related, but then death is always a special case.

A fourteen year old girl was electrocuted when she reached out of the bathtub and grabbed her cell phone. The cell phone was on a charger at the time. Apparently the leakage from the charger to the case of the cell phone was enough to electrocute her. Her skin was wet, dropping normal ~20K skin resistance down to something much smaller, and the leakage was through her arm into the chest and then the rest of the grounded skin area to the plumbing.

I'm sure there will be a string of lawsuits over whether the cell phone and/or charger was defective or defectively designed. The charger was almost certainly designed to meet the double-insulation standards that do not require a third-wire ground; most chargers are. Well, OK, there are quite a lot of low-dollar chargers that simply have the safety certification notices printed on them, and were never tested, saving the ~$10k certification charges to the maker.

You probably don't play your guitar while in the bathtub. Well, maybe you do. But did your hands ever get sweaty while playing?

[robrob]

A socket that close to a bathtub should have been a GFI so I'm really curious how this happened.

[g1]

I'm very curious about this one as well. And I wonder if the charger is transformer or SMPS type.

[Enzo]

Only recent vintage homes have GFIs, my 100 year old farm house certainly had none, and in fact the outlets were all two wire other than the few circuits I rewired.

[R.G.]

I think the operative word there is "should".

Modern USA education and business practices are good at removing really talented, intelligent, and inquisitive people OUT of the manual labor/service industries. So the kind of mind you'd like to have being - for instance - an electrician simply gets harvested out to higher pay careers. As a result, the folks who do electrical installation are not the people you WANT to be doing this, and there is a consistently higher error rate on installations than we'd like to see. It's the reason it's hard to find a really good plumber.

So sure, the outlet SHOULD have been properly GFI'd. Whether it was or not, or whether it was actually operating correctly, all of that mess, will be the subject of the myriad of lawsuits. It could well be that some of the people who get liability out of this are the electrical contractors.

[nosaj]

I think the operative word there is "should".

Modern USA education and business practices are good at removing really talented, intelligent, and inquisitive people OUT of the manual labor/service industries. So the kind of mind you'd like to have being - for instance - an electrician simply gets harvested out to higher pay careers. As a result, the folks who do electrical installation are not the people you WANT to be doing this, and there is a consistently higher error rate on installations than we'd like to see. It's the reason it's hard to find a really good plumber.

So sure, the outlet SHOULD have been properly GFI'd. Whether it was or not, or whether it was actually operating correctly, all of that mess, will be the subject of the myriad of lawsuits. It could well be that some of the people who get liability out of this are the electrical contractors.

Just got a VocoPro Karoke machine in for repair I thought it was odd it has a 2 wire plug from the factory. This thing is not that old.
nosaj

[nickb]

Just got a VocoPro Karoke machine in for repair I thought it was odd it has a 2 wire plug from the factory. This thing is not that old.
nosaj

Look on the rear, if you see a symbol of a square within a square then it is a double insulated Class II appliance and does not require a safety earth.