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amp hum/noise messa mark iv

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metalshred

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HI all,I am new here and looking for help with and amp.
I have a messa boogie mark iv head,as of late it started humming bad,its quiet when nothing is plugged into the input jack but as soon as you plug in it starts to hum,if I turn the volume on the guitar down it goes away,it even hums like this with just the cord pluged in to.I have checked all the tubes and they seem to be fine,I switched them out with the old ones that were still good and it did the same thing,I tapped them and none made sounds,the tubes all glow nice and have no spark when powered up.I cleaned all the input jacks.the amp sounds good its just the hum is over annoying.the hum gets louder as you turn the volume knob up,it goes away at 0 volume.I did check the cables,speaker and guitar.
any help would be appreciated.
 
Last edited:
HI all,I am new here and looking for help with and amp.
I have a messa boogie mark iv head,as of late it started humming bad,its quiet when nothing is plugged into the input jack but as soon as you plug in it starts to hum,if I turn the volume on the guitar down it goes away,it even hums like this with just the cord pluged in to.I have checked all the tubes and they seem to be fine,I switched them out with the old ones that were still good and it did the same thing,I tapped them and none made sounds,the tubes all glow nice and have no spark when powered up.I cleaned all the input jacks.the amp sounds good its just the hum is over annoying.the hum gets louder as you turn the volume knob up,it goes away at 0 volume.I did check the cables,speaker and guitar.
any help would be appreciated.

Maybe a coupling capacitor is shorting out.
that would be my guess

-Ben
 
perhaps, a case of return wire break(i mean shield wire). Otherwise, the equalizer set for peak of 20 to 50Hz range, like bass boost.
finally check the post rectifier filter section. if the equipment is aged(obviously, being valve model) better to replace electrolytic capacitor filters.
 
You dont need to go poking about in the power supply, if it was the power supply that was faulty it would hum constantly, whether anything was connected or not. This sounds to me like a faulty guitar lead, broken earth connection or a faulty input socket.
 
You dont need to go poking about in the power supply, if it was the power supply that was faulty it would hum constantly, whether anything was connected or not. This sounds to me like a faulty guitar lead, broken earth connection or a faulty input socket.

Yep, I agree. Check for bad solder connections on the input socket ground.
 
Check all resistors for being oopen or high, especially the screen grid ones, and check all bypass capacitors for being open or way low.
Watch your fingers, these amps bite hard, you have been warned... :)
 
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