[DMcMahon]

Ken you have successfully connected and measured several DC voltages already, so nothing really different.

For any DC voltage measurement the -ve (negative) lead of the test meter should always be connected to the -ve connection at the unit, in this case the black lead at the large capacitor. The -ve lead of the test meter would normally be black and the meter connection will be black and often called "COM" (common).

The red +ve (positive) lead of the test meter should be plugged into the red terminal on the meter identified as V (depending upon the meter there may also be other additional markings). So the red lead is the lead to connect to the various points that you want to measure, leaving the black meter lead on the black wire connection at the capacitor.

For DC voltage measurements you must switch the test meter (normally a rotary switch) to the DC voltage setting that is identified as V with 2 lines above, the top line being unbroken and the lower line broken into 3 segments.

Note - The -ve connection in a circuit may sometimes also be referred to as Ground/GRD (particularly if the line is earthed), 0V (zero volts), COM (common) etc.

For AC voltage measurement both the red and black leads have to be connected across the AC voltage source, so in your case the leads should be connected to the 2 terminals on the black REC 41A bridge rectifier that the 2 wires that connect back to the mains transformer secondary winding. The other 2 terminals on the REC 41A are the rectified DC voltage output. The test meter should be switched to AC voltage which normally is identified as V with a wavy line above it.

Meter references above are for modern Digital Multimeters (DMM), similar but slightly different for Digital Voltmeter (DVM) and analogue test meters. Note - digital multimeters are often referred to as DVMs.

David