Selenium rectifiers in Zenith radios

[NoPegs]

Originally Posted by Tubejunke

I didn't see this anywhere in this thread, but if I missed it we can just call it a good reminder. In regards to both VOMs and DMMs and measurements of current (Amperes) I submit the following: The meter must be wired in series with the circuit being measured. So, unless you have an "amp clamp" meter or attachment, you must break the circuit open wherever you choose and connect each lead to each end of the broken circuit. Current measurements can not be made in parallel.

Also, the range selector must me set to Ampere measurement and the leads inserted into the correct jacks specifically designated for Ampere measurements. Anything different will cost you money. To what amount depends the meter type.

Add one more thing here: Meters have a duty-cycle derating on them. So if your meter has a 20A AC range, that means it can measure current draw up to 20.0 A, but you can't do that indefinitely. Usually its specified as "Continuous up to X Amps, no more than one minute in five between X and Y Amps, and no more than 30 seconds in 10 minutes at Z Amps." with X commonly being 4, Y being 10, and Z being the max rating of the meter. Failing to abide by this results in a cooked current shunt inside the meter, or at the very least wildly inaccurate measurements due to thermal issues.

Also note that the derating curve is very different for the AC Amps and DC amps settings, try not to confuse the two.