Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: mcamelo on December 03, 2020, 06:02:16 pm
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Hi, all.
I've noticed that my recently built 5e3 makes a audible pop when I touch any grounded part in my guitar. After further investigation, I determined that it happens with a lead plugged into any of the four input jacks. A guitar does not need to be plugged at the other end of the lead. The pop happens if I touch any grounded metal part of the amp or the lead. It does not happen if no lead is plugged into the amp. The pop is not too loud, just loud enough to be audible.
Grounding issue?
Just checked and it also happens with my Egnator Rebel 20, so maybe something to do with the electricity circuits in the house? Amps are connected to an AC filter with an "Earth" indicator that tells me I have proper grounding.
Any ideas?
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I guess I'm not familiar with an AC filter on your mains . . . Could that be the problem? Is it an isolation transformer?
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House ground or guitar ground issue ; any mod on guitar ?
You have to check you house wall outlet grounds.
A/C filter will not help.
Volmeter on ac scale;
One probe lead plug on hot side of the wall outlet hole, the smaller one
Other probe lead plug on the wall outlet ground hole ; you may must close to 120 ac voltage .
No voltage or very low = no good ground.
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Guitar ground test
Voltmeter on ohms scale
One probe lead touch outside of output guitar jack.
Other probe lead touch the strings, bridge and all other metal parts reading should ne close to 0 or 2-15 ohms
If not ; ground issue
I read 12 ohms on my Strat. With bad contact with probes leads I read 300 ohms
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Alternatively you could puchase an outlet tester at lowes or h depot.