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FDP Forum / Fender Amps: 1985 - Current / Grounding Issue with Fender DRRI?

Humphreyplugg

Uk

Sep 5th, 2016 02:41 PM   Edit   Profile   Print Topic   Search Topic

Hi

I recently noticed a fairly loud humming noise coming from my Gibson Les Paul Studio when plugged in to my Fender Deluxe Reverb Reissue amp. The humming noise goes away when I touch metal on the guitar, or touch the strings.

I originally thought this was a grounding issue with the guitar. I took the guitar to a local tech but when he tested the guitar on his amps it was totally quiet. The tech suggested this indicates a grounding issue with the amp itself.

When I got home I tested my single coil guitars to see if there was a similar hum. When I plugged the Tele into the amp there was a distinct hum, but not as loud. I have to turn it up a bit to get the same effect. Again the hum goes away when I touch metal or strings on the Tele.

I'd be really grateful if anyone can give me their opinion as to what is wrong with my amp.

many thanks

John

reverendrob
FDP Data Goon
Moderator

When I sin

I sin real good
Sep 6th, 2016 12:53 AM   Edit   Profile   Print Topic   Search Topic

Did you try changing cables first, before you blame the amp?

Humphreyplugg

Uk

Sep 6th, 2016 03:38 AM   Edit   Profile   Print Topic   Search Topic

Yes forgot to say, bought new cable and tried that, but same issue



reverendrob
FDP Data Goon
Moderator

When I sin

I sin real good
Sep 6th, 2016 03:53 AM   Edit   Profile   Print Topic   Search Topic

Try a different outlet, different room, different building.



Te 52

Laws of Physics

strictly enforced
Sep 6th, 2016 10:27 AM   Edit   Profile   Print Topic   Search Topic

Sounds like you have a noise source in, or near, the room you're doing the testing in. Could be fluorescent lights, dimmer switch, CRT monitor, fan motor, any number of things.

Try changing the orientation of the guitar (i.e., face it north, south, east, west, up, down, etc.) If the hum changes, it's not the amp.

By the way, when noise reduces or disappears when you touch the strings or other metal parts, it's an indication that the guitar does NOT have a grounding problem.

Humphreyplugg

Uk

Sep 6th, 2016 04:11 PM   Edit   Profile   Print Topic   Search Topic

Thanks for the replies. I tried the amp in different rooms in the house, but still have the same issue. Adjusting the angle of the guitar makes no difference,

The hum only started this week and have been playing through the amp in this house for years without issue.



Humphreyplugg

Uk

Sep 6th, 2016 04:11 PM   Edit   Profile   Print Topic   Search Topic

Thanks for the replies. I tried the amp in different rooms in the house, but still have the same issue. Adjusting the angle of the guitar makes no difference,

The hum only started this week and have been playing through the amp in this house for years without issue.



MLC
Contributing Member
**********
***

It's not just good..

...it's good enough.
Sep 7th, 2016 06:48 AM   Edit   Profile   Print Topic   Search Topic

If you've been playing it for years, it may be time for some new tubes.
Since it seems like maybe a ground or power related issue, try a new rectifier tube. Just a guess, but it's a place to start.

willie
Contributing Member
*******

Too Near Atlanta GA

Amp Tech Emeritus
Sep 7th, 2016 09:47 AM   Edit   Profile   Print Topic   Search Topic

Well, there is a possibility that you have an issue with grounding on an input jack. Those 037117 plastic frame jacks will upon occasion present with a cracked solder connection due to physical stress from the plug being pulled or flexed. If you gently rotate the plug while it is in the jack during operation, you might get an indication if this is the case, however, sometimes the solder or other grounding flaw can be a bit more difficult to find and will require an expert's eye on the PCB inspecting it with a lighted magnifier.

w

tuninguitars

Indiana

lets take it apart
Sep 8th, 2016 08:10 AM   Edit   Profile   Print Topic   Search Topic

Try checking for continuity with a VOM meter from the ground prong of the AC plug to the amp chassis

also on the instrument cord ground side to amp chassis

(This message was last edited by tuninguitars at 10:13 AM, Sep 8th, 2016)

FDP Forum / Fender Amps: 1985 - Current / Grounding Issue with Fender DRRI?




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