From: rcpage@eos.ncsu.edu (ROBERT CLAUDE PAGE)
Subject: Reply: Rejuvenating Your Old Tube Amp
Originator: rcpage@c00059-100lez.eos.ncsu.edu
Reply-To: rcpage@eos.ncsu.edu (ROBERT CLAUDE PAGE)
Organization: North Carolina State University, Project Eos
Date: Thu, 23 Jul 1992 02:15:12 GMT


Grounding is not a problem. First I want to give you an idea of what is going
on when you ground your two prong amp by using a three prong plug.

Every amplifier is built on a metal chassis(at least all of mine are) and
housed in a wooden or plastic cabinet. When you turn your amplifier on the
circuitry in the amplifier charges up with current. The chassis also charges
up with electrons if it is not grounded. The charge on the chassis is waiting
to discharge to a lower potential. When you touch your turn table it is most
likely grounded and the charge built up on your amp chassis runs through (or
over) your body and discharges through your turntable and its ground.

The way to solve this problem is very easy for everyone who has a two-prong
plug amplifier (Bandmaster or Super Reeeeverrrrrrbbbbb included). The simple
fact is the chassis of your amp needs to be grounded. You will need to buy
at least two items. The plug and some power cord that provided the positive
negative polarity wire plus a grounding wire. Any hardware store will have
these items. Check the current two-prong plug on your amplifier. If they are
both the same size (one prong is not bigger than the other) then there is not
need to worry about the polarity when rewiring the new cord and plug. If there
is a difference in size then this will have to be considered. I will address
this soon. For now I'm going to provide instructions assuming that
the polarity does not madder.

1) Unplug your amplifier!!!
2) Turn you power switch on and let the amplifier sit for 10-30 minutes.
        This allows the hugh power capacitors to discharge. The electricity
        stored in them can be hundreds of volts(espically for tube amps)
        and produce a lethal shock!!!
3) Open the chassis, it may have to be removed from the cabinet, and find where
the  wires go to. Desolder, cut, unscrew the wires from the posts they are
connected to.

Note:   positive polarity (hot lead) is indicated with red wire
        negative polarity is indicated with white wire
        ground is indicated with a black wire
        (unfortunately this is not always the case on some amps)
        For the amps where polarity doesn't madder this is not a problem.

4) strip the wire to the copper (metal) and connect the wire to the posts where
the old wire was removed. Leave the third grounding wire alone right now.

5) TO GROUND THE CHASSIS. Connect the ground wire to any part of the chassis.
Be sure it is the chassis and not part of a circuit board or active circuitry.
You will fry your amp!!!!!
This can be done by soldering the wire to the chassis (the best option for good
electrical contact) or wegged between the chassis and a screw.

6) At the plug end connect the polarized wires to the normal thin prongs.
        Connect the ground wire to the large rounded prong (third prong).
        Instructions should come with the plug. It may be possible to buy a
        cord with the plug already attached; therefore, all that needs to be
        done is attach the other end to the posts and chassis.

This should properly ground the chassis. The charge will not build-up on the
chassis but run to ground. You may still get a shock when you touch your
turntable but it will not be as noticable. You may be surprised to find that
your 60Hz humm has quited some also.

If anyone wants information on how to fix one that needs to have polarity
considered then post it in the newsgroup and I'll respond. If you have any
questions respond with news or email me at rcpage@eos.ncsu.edu.

rcpage@eos.ncsu.edu
Robert C. Page IV, Electrical Engineering