This guy has one, with schematics. There's a link there to a complete "construction manual."
Here's the power supply section:
Check to make sure that C-2 is OK and doesn't leak. The radio amateur linked to above mentioned that the housing is live if you connect it to the outlet the wrong way around (C-2 goes the chassis ground.) If C2 leaks, then you'll have a "hot" housing without the ground or a tripped breaker with ground.
It may be best to replace C-2 with a Y-rated part for safety. (Y-rating)
That'd be a 2nF Y-rated filter capacitor. A Y-2 should be sufficient.
You may want to reconsider using a three pole grounded plug. The ground would normally go to the chassis.
In this meter, the chassis ground is also one end of the meter input.
If you ground the chassis, then trying to measure the voltage from an outlet has a fifty/fifty chance of causing a short circuit.
The chassis is normally floating and is not a shock hazard despite using around 90VDC for its operation.
The more I look at it, the more I think trying to ground the chassis is a bad idea. You would know not use try to measure the voltage from an outlet with it, but someone else may not - it would be a complete and unwelcome surprise to find that out the hard way.
Replace the power cable with a polarized two pin cord.
Check all the wiring to the switch, C2, and the transformer. Replace anything that is cracked, add more insulation around anything that could possibly wear through or get bent into contact with live wires.
Here's the power supply section:
Check to make sure that C-2 is OK and doesn't leak. The radio amateur linked to above mentioned that the housing is live if you connect it to the outlet the wrong way around (C-2 goes the chassis ground.) If C2 leaks, then you'll have a "hot" housing without the ground or a tripped breaker with ground.
It may be best to replace C-2 with a Y-rated part for safety. (Y-rating)
That'd be a 2nF Y-rated filter capacitor. A Y-2 should be sufficient.
You may want to reconsider using a three pole grounded plug. The ground would normally go to the chassis.
In this meter, the chassis ground is also one end of the meter input.
If you ground the chassis, then trying to measure the voltage from an outlet has a fifty/fifty chance of causing a short circuit.
The chassis is normally floating and is not a shock hazard despite using around 90VDC for its operation.
The more I look at it, the more I think trying to ground the chassis is a bad idea. You would know not use try to measure the voltage from an outlet with it, but someone else may not - it would be a complete and unwelcome surprise to find that out the hard way.
Replace the power cable with a polarized two pin cord.
Check all the wiring to the switch, C2, and the transformer. Replace anything that is cracked, add more insulation around anything that could possibly wear through or get bent into contact with live wires.
Attachments
Whoops. Right capacitor, wrong number. I meant C-1 above about the Y capacitor.
I don't know the regulations in the US, but here in Germany you aren't supposed to use a grounded cable on an ungrounded appliance. The ground pin on a grounded cable must always be connected to a safety ground on the device.
There's probably a similar regulation in the US.
There are two conductor removable cables that are polarized. I'd use one of those.
I don't know the regulations in the US, but here in Germany you aren't supposed to use a grounded cable on an ungrounded appliance. The ground pin on a grounded cable must always be connected to a safety ground on the device.
There's probably a similar regulation in the US.
There are two conductor removable cables that are polarized. I'd use one of those.
Thanks again, I will try to locate an appropriate polarized 2 prong cord and ac receptacle. I have located a Y-2 safety capacitor and it will be the first replacement, since the original is a paper/wax capacitor and 65 years old. All of the capacitors in the meter will be replaced with modern equivalents.
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