OT: how to hook up a dummy load resistor when scope biasing?

[nightingale]

hello~
i just got an old scope, and i want to see if my old twin reverb has crossover distortion.. or mostly get a feel of what the "notches" look like on the wave.. simply because i have never seen them before..

i know that i need a dummy load resistor hooked up to the output, but i am not sure of the value.. or the voltage? or how to hook it up..?

could i just wire the dummy load resistor to a jack.. right across the hot/ground lugs? and plug the output cable into the jack?

my neighbor has a signal generator that i am asking to borrow.. i just want to know what i am doing beforehand..

i understand that the proper way to bias a tube amp is a controversial subject... but i am just trying to get some use out of my new scope.

[The Tone God]

You need a dummy load of the right resistance and wattage. So with a twin reverb you need a 4 ohm 100 watt load. Wire it in like a speaker and take your probe reading across the load.

Andrew

[freebird1127]

If you're looking for crossover distortion, here's what you're looking for:  This happens in push-pull amplifiers when the two "pushing" transistors switch at different times.  If designed properly, and the components are fine, the positive half-cycle transistor will switch on at the same time the negative half-cycle transistor is switching off, and vice versa.  If malfunctioning, you might see a lag between the end of one transistor cycle and the beginning of the next.  That's crossover distortion:  The signal literally distorts as it crosses over the reference line.

Good luck  :wink: