I think I have a tube problem...help diagnosis PLZ

[falloutboysuXXX]

whenever i turn up my tube amp i get a strong low hum. i replaced all of my tubes almost two years ago, and i know i should replace the power section pretty soon, but is that what's causing the problem?

thanks for your help. i mean, thx 4 ur help a millz brawz!

 

[Dave Z]

Re: I think I have a tube problem...help diagnosis PLZ

Could be a tube, a dirty shorting plug (input jack), or it could be a filter cap going. In which case, you do not want to fix this yourself, voltages inside a tube amp EVEN WHEN TURNED OFF AND UNPLUGGED can kill you. The filter caps store electricity.

As for tubes...you can safely debug the preamp & PI tubes, by replacing them them with a known good tube one by one. starting by the inputs. If the hum goes away when you've replaced one, thats the bad one. If that does not do it, you can replace power tubes, maybe a buddy has a couple you can borrow for the debug.

Does it hum with a guitar plugged in? Without anything plugged in?

 

[Lake Placid Blues]

Re: I think I have a tube problem...help diagnosis PLZ

It can be any number of things:

If it's a class A/B amp it could be improperly set bias. Too hot.

Also, if the hum follows notes as you play; it could be weak filter caps.

Hums can be caused by worn out preamp tubes, particularly the V2 in a Marshall. I've had this problem with even brand new current production 12AX7's.

Additionally, be aware that no amp is totally quiet. Usually the signal to noise ratio is such that the noise isn't noticed. However, turned way, way, up, with no signal, the noise floor may become much more noticable.

 

[skyydogg01]

Re: I think I have a tube problem...help diagnosis PLZ

falloutboysuxxx???

I thought you died

 

[falloutboysuXXX]

Re: I think I have a tube problem...help diagnosis PLZ

thanks for the replies. what might the ramifications be if I prolong use without addressing the problem immediately?

 

[falloutboysuXXX]

Re: I think I have a tube problem...help diagnosis PLZ

oh, and for the record, though I have not yet encountered death, i have come close upon ingesting mescaline. that trip came with probably 3 near death experiences.

 

[jimmy]

Re: I think I have a tube problem...help diagnosis PLZ

And he's back.

 

[ginormous]

Re: I think I have a tube problem...help diagnosis PLZ

IMHO, hum = grounding prob/partial short. Have someone you can trust check the signal path, esp. the jacks & pots. After which, chase the tubes.

Surgeon Gen'l's Warning: Failure to eliminate a grounding problem will lead to signal failure, amp smoke, excessive expenditure of hard-earned cash, or possible death. If you can get in touch with him, maybe Keith Relf :newangel: can fill in the rest.