50/60 Hz Humm

  • Thread starter Thread starter karambos2
  • Start date Start date
karambos2

karambos2

New member
Hi,

sometimes, when I switch my guitar amp on, I get a terrible humm. It's a constant tone and it won't go away. Sometimes it goes on for hours and I don't know what it is. Other times it stops after I pull out the plug and push it in again.

I've heard of 60 Hz groundloop humm and as we in Germany have a different voltage I guess it would be 50 Hz humm.

I've got a 1922 Marshall Cab and 2195 JMP Lead & Bass, 100W head manufactured sometime between 1976 and 1980.

Can anyone help me to get rid of this darned humming?

Thanks in advance
 
Have it checked/serviced - it's not normal (obviously!)
 
I bet your playing Fender guitar... if so, look into getting some noiseless pickups for it... oh, and stay away from gas type lights and etc.
 
It sounds like the hum could be caused by a ground fault, especially since you mention that it sometimes goes away after moving the plug around.

My first step would be to isolate the problem to see whether the amp/cab is at fault or if it's the power supply.

Have you tried plugging it into a different circuit/power outlet, or in a totally different location (as in a different house)? I would also check the power cord to make sure there's no problem there, as it could have a bad connection or loose wire in the plug.

If it still hums after having tried that, then the problem is with the amp and I would definitely recommend taking it to an amp tech. There can be a high voltage buid-up in an amp, even if it's turned off and disconnected from the power supply. Be careful taking it apart and putting your fingers in there unless you know what you're doing!
 
Hi there,

I spoke to someone about it today and they said I should lift the ground. So I did. It still humms.

So I left it humming and unplugged all the other devices: synths, lamps, the fridge, ventilator fans, heaters etc until NOTHING was left plugged in apart from the amp and it still humms. Even when it's the only thing plugged in.

Then I realised that the plug sockets and the lights are on the same circuit.

Could that be the problem?

It's an old transistor am, like from 1976. Could it be a problem with the transistors? Apparently they "dry out" after 20 years or so.

I'm grateful for any help
 
karambos2 said:
Other times it stops after I pull out the plug and push it in again.
Click to expand...

If this is the situation, you probably have a poor connection (cold solder joint, faulty connector, dirty contacts, etc.), most likely in that jack (I am assuming you mean the instrument jack when you say plug). It may be fixed by contact cleaner, replacing a jack, or re-flowing a solder joint.

If this is not the case (and you mean the power plug), you really would need to take it to a repair facility to have it properly checked (to reiterate Bruce's - and other's - points).

NOTE:::: If you do not have adequate experience in electronic/electrical devices, do NOT open the unit to "have a look", especially if the power is on. There are lethal voltages present (even with the power disconnected). (Pennylink already mentioned this, but some things "bear" repeating ;) )

Mike
 
Checkout www.guitarnuts.com for some explanation of how to maybe shield your guitar. This will knockout most of the background interference your guitar will be picking up, ie hum from lights, monitors, tv's *radio waves* etc.

Once the guitar is shielded think about some noiseless pu's or humbuckers.

Also it is to be remembered that single coil pu's have a 50 or 60 hz hum always due to the electromagnet creating self noise. There is no way of getting rid of it, but it shouldn't be too loud really.

As for sourcing problems in the amp, I can't really help much I'm afraid.......
 
@ teknomike - I didn't mean the instrument jack, I meant the plug socket where you plug it into the mains supply. The amp humms even when there's no instrument plugged into the jack sockets.

I'm going to get the thing fixed. I hope there's a Marshall shop in town.....

Thanks to everyone for their advice.
 
Not to beat a dead horse, but have you plugged it in somewhere else other than where you normally use it? I mean, in a different building altogether?

It would be a shame to spend money having someone look at it, only to tell you that it's the power supply in your house that's the problem due to a ground fault...

I know this might only be a small possibility, but it would seem to be worth the trouble if you haven't tried that yet.

In any case, good luck getting rid of that hum. I know I couldn't stand it, either!
 
I tried it at home and it was fine. But up until a few days ago, it was fine in the studio, too!!

Suddenly, it humms no matter what I do!
 
You must log in or register to reply here.
Back
Top