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Hi guys I have a 73 super which I noticed halfway through our set we started hearing what I thought was mic feedback but it ended up being my amp. It did it twice the first night very high pitched ring/ feedback. I had 6L6 feedback once before that's are going bad but this did not sound like that at all. When I first bought the amp I had to replace the lines going into the reverb tank and after putting new tubes into the amp two weeks ago it started to do the same thing but the ring didnt get near as bad as the first time. Thanks Derek c Nebraska!
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New tubes two weeks ago - power or preamplifier? All, just a few? One at a time? That's always a first suspect...
Second would be ground connection gone bad... how're your filter caps?
Justin"Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
"Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
"All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister - -
Does it do this with the reverb turned all the way down?
6L6 feedback will be lower pitched, usually more like a rumble. Preamp tube feedback is usually a high pitched squeal.Originally posted by Enzo
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Yes^^^
Turn the reverb down to zero, still do it?
When it does this, put on a glove or use a rag, and grip each tube firmly in your hand, going down the row. Does gripping any of the tubes affect the noise? Does turning the controls on the panel to zero affect the noise?
DOes turning the volume control on your guitar affect the noise?Education is what you're left with after you have forgotten what you have learned.Comment
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It's only happened 2hrs in on a 4hr set. Reverb pretty sure was on when this happened. I changed all the preamp tubes. Switching standby stops the feedback.Comment
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So next time it happens, zero the reverb real quick to see if involved.
Also with reverb off, ball up your fist and whack the top of the amp to reveal any loose connections.Education is what you're left with after you have forgotten what you have learned.Comment
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Plugged the super in and noticed through the external speaker jack flashing red light like an arc.Comment
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Not saying not to check, but that may well be the tremolo "bug" flashing. It's a small light bulb & resistor together in shrink wrap. Sometimes, for whatever reason, some light gets out of the little shrink wrap casing. Was it a steady flashing, and can you change the speed with the tremolo controls?
Justin"Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
"Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
"All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -Comment
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That's exactly what it is. Thanks I'm new to amp repair been playing 20years itching to learn to repair and mod these things now.Comment
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If you're new to this and want to learn more, take a look at Jack Darr's 'Guitar Amplifier Handbook' - a quick search will get you a free (legitimate) PDF copy.
Old, but sound.Comment
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