The Steel Guitar Forum

i just changed my output transformer on a 59 RI fender bassman. I put a super/concert O.T. in it because it has three taps for 4/8/16 and they weren't labeled. So I took a guess and used the solid green wire. I used my cheap GB instruments mutimeter and tried to get an Ohm reading to see if I got the 8 ohm tap. I can't get an ohm reading! it goes to 0. Maybe my meter is bad because when I set the multi-meter to the RX1k or RX10 and attach the leads to my speaker I get a 0 reading just as I do when I attached them to the speaker outs on the amp.

What am I doing wrong?

Thanks,

Steve

get a digital meter and set it to it's lowest range, most lowest are around 200 ohms

Resistance is a DC measurement. A coil also has reactance which is an AC measurement. X = 2*pi*f*L where L is measured in henries. Impedance is the complex sum of the two, Z = sqrt(x^2 + R^2). An output winding has only a few turns of heavy wire, so it's expected that the DC resistance would be near zero.

If you care to spend about $20, you can get an RLC meter that will measure resistance, inductance, and capacitance. If you do, be sure you get one with a range to measure your filter capacitors.

Steve, the "Rx100" means the first mark on the meter scale is 100 ohms. In that case, you could not see a reading of less than 100 ohms. If you use an analog meter, it will need a Rx1 scale in order to see one ohm. If you use a meter that will display a reading that is above zero, the 4 ohm tap will be the lowest resistance. The 16 ohm will be the highest resistance. The resistance readings are DC resistance and do not represent impedance.

Also, Steve, just because you want the 8 ohm tap doesn't mean that the TRANSFORMER should read 8 ohms - it means the SPEAKER should read 8 ohms (nominal impedence, more or less, as explained above). I don't know what the transformer's secondaries should read, but, once you get your meter sorted out, you can measure all three wires, and the 8 ohm tap would be the middle reading.