From LORD_VALV–(at)–rodigy.net Sun Feb 7 16:16:33 CST 1999
Article: 157502 of alt.guitar.amps
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From: “LORD VALVE”
Newsgroups: alt.guitar.amps
Subject: Re: Weird problem with silverface twin
Date: Sun, 7 Feb 1999 01:55:06 -0700
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Xref: geraldo.cc.utexas.edu alt.guitar.amps:157502
Robert Orr wrote in message …
>I replaced the 100K plate resistors in my twin, changed the slope resistor
>to 56K, put in a lower value cap on the bright switch. The amp sounds
>great OUT OF THE CABINET. BUT…… when I put it in the cabinet, some
>weird grounding thing causes the amp to howl uncontrolably. This happens
>when the amp is totally in contact with the sheild on the inside of the
>cabinet. AND… when it is only partially in contact, (just sitting in
>the cabinet, not held in with the bolts) I can plug in my guitar and make
>the amp “go to 10” with the volume all the way off on the amp. This is
>triggered just by plugging a cable into the input jack. (I only use the
>vibrato channel, the normal channel is disabled)
>Its as if plugging in the cable causes the volume control on the amp to
>short out. Also, when I turn the volume control on my guitar down, the amp
>gets more and more hum.
>
>None of these symtoms are present when the amp is not in physical contact
>with the cabinet.
>
>Anybody got any sugesstions as to what would be causing this weird
behavior?
>
>Thanks,
>
>Robert
Lord Valve Speaketh:
If the shield is the old window-screen type, make sure that none
of the little wires from it are poking down into the amp chassis…
those can play hell with anything they touch inside. If you have
the aluminum plate type, check to make sure none of the internal
parts are sticking up far enough to touch the plate. The easiest
way to do this is to put a ruler across the top of the chassis and
slide it back and forth over the whole length of the amp…if anything
touches the ruler, push it down.
Lord Valve
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