2 to 3 Prong Conversion
Converting old style Fender 2 prong (ungrounded) power cord amps to a 3 prong (grounded) is not a difficult endeavor. One only has to move one of the power supply primary wires from the out side fuse terminal to the ground switch terminal that connects to the aux.pwr.plug jack, that has the white wire coming in from the power cord. Move the wire from the center connector of the fuse holder that connects to the ground switch on the left to the right side. The only other thing one needs to do is connect the green wire from the 3 prong power cord to a suitable ground. This is easily accomplished by crimping a ground lug on the wire and unscrewing one of the nuts on the power transformer closest to where the power cord comes into the chassis and tightening it down on this new ground lug.
NOTE: *ANYtime* you're inside an amp you run the risk of
getting yourself shocked! This comes from the electrolytic capacitors in the
power supply that act as a 'filter section' - turning the AC coming in to a
(more-or-less) useable DC.
The absolute easiest way to take a 'jumper cable' (2 alligator clips connected on a wire) and short (or attach) one end to the chassis on a 'lip', or other metal point that it will stay on, and the other end on the first preamp tube, either pin 1 or pin 6 . These pins go to either one of the plates of the 2 triodes (there are actually 2 'tubes' in each 12AX7 preamp
tube) of your preamp tube. You might as well use the first tube, all the way on the right, looking from the back of the
chassis. ...anyway, after you've connected this shorting-jumper-cable, and with the AC cord ***UN-plugged*** turn on the power and standby switches... and after about a minute MOST of the 'juice' will drain out of the caps. I do this
religiously before I do *anything* inside an amp, and have not been shocked by following this procedure.
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Last updated Jan 2nd, 2001
by Uncle Spot