At what kind of voltage will a mains test screwdriver start to glow?
 

I appreciate that this will of course vary from manufacturer to
manufacturer, but in general terms can someone give the approximate
voltage? I'm curious because I'm getting a "glow" from the outer
metal casing of a SCART lead connector on several pieces of
equipment.

At what kind of voltage will a mains test screwdriver start to glow?
 

"Tov" wrote in message
...
I appreciate that this will of course vary from manufacturer to
manufacturer, but in general terms can someone give the approximate
voltage? I'm curious because I'm getting a "glow" from the outer
metal casing of a SCART lead connector on several pieces of
equipment.

**Depends on the screwdriver. One of mine starts at around 12 Volts.
However, it is an LED, powered type. The usual, neon types start at around
65 Volts. It's not unusual to detect minute leakage currents from domestic
equipment. Disconnect everything and test separately. You'll probably find
it'll be the antenna. Some US equipment has a resistor from neutral to
chassis. If this has been mis-wired or there is a fault elsewhere, you'll
get leakage from that too.

Trevor Wilson

At what kind of voltage will a mains test screwdriver start to glow?
 

Trevor Wilson wrote:

"Tov" wrote in message
...
I appreciate that this will of course vary from manufacturer to
manufacturer, but in general terms can someone give the approximate
voltage? I'm curious because I'm getting a "glow" from the outer
metal casing of a SCART lead connector on several pieces of
equipment.

**Depends on the screwdriver. One of mine starts at around 12 Volts.
However, it is an LED, powered type. The usual, neon types start at around
65 Volts. It's not unusual to detect minute leakage currents from domestic
equipment. Disconnect everything and test separately. You'll probably find
it'll be the antenna. Some US equipment has a resistor from neutral to
chassis. If this has been mis-wired or there is a fault elsewhere, you'll
get leakage from that too.

Add to that the fact that most switching PSUs contain Y capacitors for EMI
suppression that also cause a leakage current to ground. If the equipment is
ungrounded, such parts can rise in voltage to around half the supply voltage
if measured into a high impedance. The leakage current is quite low however,
typically under a hundred microamps..

Graham

At what kind of voltage will a mains test screwdriver start toglow?
 

Tov wrote:
I appreciate that this will of course vary from manufacturer to
manufacturer, but in general terms can someone give the approximate
voltage? I'm curious because I'm getting a "glow" from the outer
metal casing of a SCART lead connector on several pieces of
equipment.


I think you're right to be concerned. Can't tell where you are,
whether you have safety grounds on the power plugs etc.
I have zero experience with SCART, but pinouts.ru claims that
the shield is chassis ground. The whole idea of a safety ground
on the power system is to NOT have voltage on the shield/chassis.

I'd borrow an actual voltmeter and measure from the sheild to actual
ground. Measuring to the power system safety ground may not help if
that's the thing that's compromised. Unplug equipment until the voltage
goes away. Then address the problem for a specific piece of equipment.
Random remote conjecture from the web is no substitute for actual
measurements.

I've had the pee, literally, shocked out of me when the safety ground in
the house wiring went open. On a related note, I've also seen high
leakage current when a cat decided to take a pee on the equipment.

At what kind of voltage will a mains test screwdriver start toglow?
 

On Dec 10, 8:53 am, mike wrote:
Tov wrote:
I appreciate that this will of course vary from manufacturer to
manufacturer, but in general terms can someone give the approximate
voltage? I'm curious because I'm getting a "glow" from the outer
metal casing of a SCART lead connector on several pieces of
equipment.

I think you're right to be concerned. Can't tell where you are,
whether you have safety grounds on the power plugs etc.
I have zero experience with SCART, but pinouts.ru claims that
the shield is chassis ground. The whole idea of a safety ground
on the power system is to NOT have voltage on the shield/chassis.

I'd borrow an actual voltmeter and measure from the sheild to actual
ground. Measuring to the power system safety ground may not help if
that's the thing that's compromised. Unplug equipment until the voltage
goes away. Then address the problem for a specific piece of equipment.
Random remote conjecture from the web is no substitute for actual
measurements.

I've had the pee, literally, shocked out of me when the safety ground in
the house wiring went open. On a related note, I've also seen high
leakage current when a cat decided to take a pee on the equipment.

I'm measuring about 150V AC, which in the UK is over half the supply
voltage. And it doesn't appear to be just one piece of equipment.
Graham (Eeyore) above has an explanation. The mains test screwdriver
in question failed to light up when a car battery was being charged
(about 20V DC, probably).