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AD30 RF Interference

Posted: Mon Nov 06, 2017 3:49 pm
by Hambone
I'm picking up radio signals from my single channel AD30. I thought it was the guitar cable, but it happens with three different cables, two of which are brand new. I don't hear this with the same cables in my two other amps. I took it to a tech and he couldn't find anything wrong. Anybody else have this problem with an AD30?

Re: AD30 RF Interference

Posted: Mon Nov 06, 2017 8:54 pm
by fiveightandten
I've never had an issue with either of mine. I'd suspect that there's an issue with the amp, as opposed to this being a consequence of the design. I've never heard of this happening with an AD30.

-Are the pre-tube shields on the 12AX-7's?
-Is it a head or a combo?
-If it's a head, is the rear panel on it?

Fixes:
-Pull all the tubes out and put them back in a few times to clean the contacts off and negate any poor tube connections.
-The older head versions had a metal tray that sat on the underside of the chassis. You could order one of those from Orange if you don't have it.
-Double check that all the shielded wires are properly grounded.
-You *could* add some shielding around the input jack and pre-amp board. This would require drilling through the chassis, but you could easily fabricate something out of sheet metal. You could also install a cap between the input jack ground and the chassis. But I suspect these things will not be needed if the route cause is found.


This could be bleeding in through the AC due to bad power, or could be the cause of a bad solder bad connection on one of those push on connectors.

Re: AD30 RF Interference

Posted: Tue Nov 07, 2017 11:16 am
by bclaire
I seriously doubt it's anything wrong with the amp.

Does it happen with other guitars? Does it happen in different locations? Are the "new" cables definitely guitar cables because speaker cables can produce this problem? Try a friend's guitar through the amp with yet another guitar cable...


If the tech couldn't find anything wrong with the amp, it's probably not the amp...

Re: AD30 RF Interference

Posted: Tue Nov 07, 2017 4:24 pm
by Hambone
fiveightandten wrote:
Mon Nov 06, 2017 8:54 pm
I've never had an issue with either of mine. I'd suspect that there's an issue with the amp, as opposed to this being a consequence of the design. I've never heard of this happening with an AD30.

-Are the pre-tube shields on the 12AX-7's?
-Is it a head or a combo?
-If it's a head, is the rear panel on it?

Fixes:
-Pull all the tubes out and put them back in a few times to clean the contacts off and negate any poor tube connections.
-The older head versions had a metal tray that sat on the underside of the chassis. You could order one of those from Orange if you don't have it.
-Double check that all the shielded wires are properly grounded.
-You *could* add some shielding around the input jack and pre-amp board. This would require drilling through the chassis, but you could easily fabricate something out of sheet metal. You could also install a cap between the input jack ground and the chassis. But I suspect these things will not be needed if the route cause is found.


This could be bleeding in through the AC due to bad power, or could be the cause of a bad solder bad connection on one of those push on connectors.

Ah, the tube shields are off. They wouldn't stay on so I removed them. I'll see if I can get a new pair. It is a head, and the rear panel is on.

Re: AD30 RF Interference

Posted: Tue Nov 07, 2017 4:25 pm
by Hambone
bclaire wrote:
Tue Nov 07, 2017 11:16 am
I seriously doubt it's anything wrong with the amp.

Does it happen with other guitars? Does it happen in different locations? Are the "new" cables definitely guitar cables because speaker cables can produce this problem? Try a friend's guitar through the amp with yet another guitar cable...


If the tech couldn't find anything wrong with the amp, it's probably not the amp...
It happens whether the guitar is plugged into the cable or not. They are brand new instrument cables, yes. I don't get any interference when I plug the same cables into other amps.

Re: AD30 RF Interference

Posted: Tue Nov 07, 2017 7:48 pm
by bclaire
Gotta be the amp then... weird.

Re: AD30 RF Interference

Posted: Tue Nov 07, 2017 8:16 pm
by Sooner
Hambone wrote:
Tue Nov 07, 2017 4:24 pm
Ah, the tube shields are off.
Bingo...

Re: AD30 RF Interference

Posted: Tue Nov 07, 2017 11:10 pm
by Hambone
I put the tube shields back on, and plugged the amp into a Furman power conditioner. I still have really loud RF interference. I tried using both a 10' and 20' cable, and it was the same.

Re: AD30 RF Interference

Posted: Tue Nov 07, 2017 11:21 pm
by Sooner
Hambone wrote:
Tue Nov 07, 2017 11:10 pm
I put the tube shields back on, and plugged the amp into a Furman power conditioner. I still have really loud RF interference. I tried using both a 10' and 20' cable, and it was the same.
That's weird. AM or FM stations? :-)

Re: AD30 RF Interference

Posted: Tue Nov 07, 2017 11:37 pm
by bclaire
Are you near a radio station transmitter?

Re: AD30 RF Interference

Posted: Wed Nov 08, 2017 2:19 am
by Hambone
I don't know if I'm near a transmitter. I just moved a couple of weeks ago, but this was an issue in my old house as well.

Re: AD30 RF Interference

Posted: Wed Nov 08, 2017 3:57 am
by bclaire
Hambone wrote:
Wed Nov 08, 2017 2:19 am
I don't know if I'm near a transmitter. I just moved a couple of weeks ago, but this was an issue in my old house as well.
Get a new amp tech....

Re: AD30 RF Interference

Posted: Mon Nov 13, 2017 6:27 pm
by Rlw59
Bad solder joints or corrosion on mechanical connections can cause your problem.

First thing to do is pull each tube and reinsert it a few times to clean any corrosion. There are spray cleaners, but you need one that doesn't leave residue/lubricant. Unless the corrosion is extreme, just the wiping action of pulling and reinserting will be enough.

If the AD30 has an fx loop, stick a plug in and out of the send and return jacks a few times. Spray cleaner would be more useful here as all you're doing is opening and closing the shorting terminal (the wiping of the plug in & out isn't touching the contact area of the shorting terminal).

If that doesn't solve it, it could be push-on connectors on the circuit board, or a cracked or cold solder joint on the board. Bad solder joints aren't always visible, and don't always cause other problems. So if cleaning the mechanical connections doesn't fix it, probably be best to reflow all the joints.

A good tech checking an amp for RF would have pulled the tubes and cleaned the jacks even if he couldn't replicate the problem in his shop. But some techs don't bother to do anything if they can't get the amp to misbehave in their shop. Just plug it in, play through it, and if no problem found they just charge you for their minimum bench fee. Can't entirely blame him -- unless he had a good conversation with you about the problem, it was fairly reasonable for him to assume the problem was more likely to be your guitar or cable (or wah pedal -- they often tune in radio stations).

If cleaning all the contacts doesn't work, make a recording of the problem. Then take it back to the tech (or a different tech) and tell him "this is what it does, and my other amps don't do this with the same guitars/cables".

Re: AD30 RF Interference

Posted: Tue Nov 14, 2017 5:46 pm
by Hambone
Will do. Thanks!