Orange amp has a very strong hum + picks radio - any idea?

[lior]

Hi everyone,

I have an Orange AD15 amp, I had it for many years and suddenly when I switched it on today it started making a loud hum noise + picking up radio.
I think it sounds like ground loop noise. I tried 3 different high quality jack leads, different power lead for the amp, a DI and 2 different guitars and nothing has changed.
It still makes this noise even if the guitar volume is set to zero, also when I touch the lead (the end that is connected to the amp) it almost stops completely. so I assume the problem is with the amp. I opened it up to check for loose wires but everything seems to be perfectly in place...

Anybody has an idea what could that be?

Thanks for your time!!!

[a.hun]

Hi lior. Welcome to the forum.

You need to be very careful if opening up the chassis yourself as there can be very high (lethal!) voltages stored by the big capacitors - even long after powering the amp down.

There are various possibilities. About the only ones you can check for yourself would be a bit of valve swapping (could be any of them I'd say) and cleaning up the input socket with a bit of electrical contact cleaner spray. If these don't help there isn't a lot more you can safely check yourself and it would be best to have the amp checked over by a good amp tech.

Good luck!


Andy.

[TheOrangeJuicer]

Probably a bad preamp tube. It could also be the input jack or its connections. Several other possibilities actually but those are most common. Try pulling the first tube (closest to the input jack) and reseating it. If that fixes it, there you go. Otherwise, try replacing it for a fresh 12AX7.

[Gladmarr]

Sounds like your input jack has come unsoldered from the internal PCB. I bet if you grab the input plug and wiggle it the noise comes and goes as you are connecting/disconnecting the jack ground to the circuit board.

[lior]

Thanks very much to all of you for such a quick response and for your great advice!

I called Watford valves in Hertfordshire to ask about the problem and possibly order new ones. They said this problem does not sound like something that's related to valves and that's probably something to do with the input connection. Since it picks up radio it's probably something to do with ground connection.
I did wiggle the valves gently and pulled them out and then back in again and nothing has changed...
When I opened up the amp the other day I did check the input connection (which was a bit loose) and tightened it up, however I could not see any loose or unsoldered wires - everything looked perfectly fine inside (although I don't really know much about electronics so I might be wrong).
I tested the amp again today: when I plug in the lead this loud noise starts + I can hear radio. when i pull the lead out it stops completely - which means this prob has to do with the input connection and not the valves, otherwise the amp would make this noise even though there's nothing plugged in.

Do any of you know a good tech based in London (preferably in North London)? or maybe give me some guidance to how to fix it myself?

Thanks again for your time - I really appreciate it!
Cheers.

[TheOrangeJuicer]

Thanks very much to all of you for such a quick response and for your great advice!

I called Watford valves in Hertfordshire to ask about the problem and possibly order new ones. They said this problem does not sound like something that's related to valves and that's probably something to do with the input connection. Since it picks up radio it's probably something to do with ground connection.
I did wiggle the valves gently and pulled them out and then back in again and nothing has changed...
When I opened up the amp the other day I did check the input connection (which was a bit loose) and tightened it up, however I could not see any loose or unsoldered wires - everything looked perfectly fine inside (although I don't really know much about electronics so I might be wrong).
I tested the amp again today: when I plug in the lead this loud noise starts + I can hear radio. when i pull the lead out it stops completely - which means this prob has to do with the input connection and not the valves, otherwise the amp would make this noise even though there's nothing plugged in.

Do any of you know a good tech based in London (preferably in North London)? or maybe give me some guidance to how to fix it myself?

Thanks again for your time - I really appreciate it!
Cheers.

If, the first tube is fine, then it's either the input jack itself, the connection from the jack to the circuit, or another connection somewhere between the jack and tube socket. Only a few places to look. It sounds like it's right at the jack though based upon you being able to stop it by touching that part. It should all be connected solidly, through to the first tube on the + side, to the chassis on the - side. Don't touch anything inside the amp other than the input jack when looking for a bad connection there. There is no voltage on the jack but lots of it all over the amp circuit everywhere else, including the first preamp tube socket.

[Gladmarr]

This s just a thought, but have you moved this amp from one room (or outlet) to another? You might just have a faulty ground on a few outlets in your house or practice space.

[lior]

Thank you all again for your advice.
However, the problem is not solved yet unfortunately...

I took the amp to a tech who specializes in building amps, valves etc.
Once i switched it on everything worked perfectly fine (we tried my guitar & leads and his), the amp was dead quiet like always.
Tried it at a friend's house - works perfectly as fine! came back home - same problem.
I borrowed a Fender Blues Junior amp from a friend to check at home and see if it introduces the same problem, however his amp works absolutely fine (although when i cranked the volume and gain to maximum I could hear a little bit of this radio I'm picking, but no hum). Tried to swap and fiddle with my valves but nothing has changed.
I still suspect that the problem might be in the building (ground loop? or perhaps voltage frequency has changed from 50Hz to something different?) and my amp isn't happy with it. Then again, I would expect the Fender amp to have the same interference.

If someone has any idea what's causing this or how to solve this problem, I'd be grateful.

Thanks!

[a.hun]

Thats annoying. I think Gladmarr probably has it though. Likely to be a grounding problem on the mains at your own place. Easy to test for. You can get plug in ground testers for just a few notes from electronics stores. If your grounds aren't good than an electrician will sort you. Totally worth doing anyway for everyday safety reasons...

No reason BTW why just because one amp picks up radio there that any and all other amps would too. That is down to internal shielding / components / layout which aren't going to be at all the same for two different amps.

FWIW I have a radio transmitter mast less than a couple of hundred meters away from my house and the amp which is most susceptible to interference from it is... my early model Blues Junior. None of my other amps give really noticable problems, but I have to position my BJ carefully to minimise noise. I also have problems with noise from all single coil pickups. For recording them I need to face directly towards or away from the transmitter and sit pretty still. At least I know what the cause is and how to get around it. There are worse things...


Andy.

[Bentfinger]

I had the same problem in my previous home, but only at times. A Furman power conditioner took care of it. Also, I have some old pedals that don't play well with newer ones, and cause weird noises.. I agree that you should check the a/c outlet voltage with a multimeter. A power conditioner is great when playing clubs. Eliminates the popping, etc when the a/c or beer cooler cuts on or off... Hope this helps