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Amp Hums when Cold, Even with Nothing Plugged In. Do I Need to Resolder Input Jack?

Started by Roark, October 17, 2022, 01:06:44 PM

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Roark

It's a Fender Frontman 15G Amp, which is useful to me because it's small enough to fit on my desk, for when I give lessons. There's a pretty loud Hum from the Amp, mainly when cold & whether or not anything is Plugged In. This is with the Amp Volume set to zero.
The Hum usually Stops after the Amp has warmed up for about 5-10 min. For awhile the Hum was eliminated by [repeatedly] unplugging & replugging the guitar cable from the input jack of the amp.But now the problem is getting progressively worse & the Hum returns, even after the Amp has warmed up [& now there's even other noises: distortion?,crackling?,static?].

I'm asking your advice to confirm whether this Hum is likely to be caused by a cold solder joint of the Input Jack?... or something else?

To isolate the problem I eliminated: the Cables, A/B Box [Splitter], Guitar & Effects Pedal I normally use.

The problem appears to be in the Input Jack because I noticed I used to be able to eliminate the Hum by pulling the cable plug/tip part way out of the input jack,to the point where the plug/tip first touches the contact in the jack ; & then pushing up & down on the plug/tip [jiggling a bit]: I  would hear the hum stop completely & there was a click sound!  But this doesn't work any more.

Roark

I guess this is a shorting/switching/shunt input jack & I wonder if that is somehow the problem?

joecool85

Quote from: Roark on October 17, 2022, 01:06:44 PMIt's a Fender Frontman 15G Amp, which is useful to me because it's small enough to fit on my desk, for when I give lessons. There's a pretty loud Hum from the Amp, mainly when cold & whether or not anything is Plugged In. This is with the Amp Volume set to zero.
The Hum usually Stops after the Amp has warmed up for about 5-10 min. For awhile the Hum was eliminated by [repeatedly] unplugging & replugging the guitar cable from the input jack of the amp.But now the problem is getting progressively worse & the Hum returns, even after the Amp has warmed up [& now there's even other noises: distortion?,crackling?,static?].

I'm asking your advice to confirm whether this Hum is likely to be caused by a cold solder joint of the Input Jack?... or something else?

To isolate the problem I eliminated: the Cables, A/B Box [Splitter], Guitar & Effects Pedal I normally use.

The problem appears to be in the Input Jack because I noticed I used to be able to eliminate the Hum by pulling the cable plug/tip part way out of the input jack,to the point where the plug/tip first touches the contact in the jack ; & then pushing up & down on the plug/tip [jiggling a bit]: I  would hear the hum stop completely & there was a click sound!  But this doesn't work any more.

Sounds like the on-board solders are broken - if you are lucky, the pads are still intact on the PCB.  If you are handy with a soldering iron, open it up and wet the joints (reheat them, ideally adding a small amount of solder at the same time).
Life is what you make it.
Still rockin' the Dean Markley K-20X
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Roark

Thanks for your reply, joecool85!

To clarify: When the amp is cold & with the Guitar Plugged In: I hear both the HUM AND the PROPER SIGNAL. The Hum disappears eventually,but may return.

Have you ever heard of [with the Guitar Plugged In] a HUM problem,in particular  [I mean vs CRACKLING or STATIC] as a symptom of a Cold Solder of the input jack?


Tassieviking

#4
I agree with Joe, it sounds like it might be the solder joints on the input jack.
It's a common problem when the socket is soldered to the pcb, every time the guitar is plugged in the socket is stressed mechanically and eventually the solder cracks.

The input jack is the shorting type from the schematic I have so it could be dirt in the socket, a quick squirt with Deoxit or similar and the stick the plug in /out several times might fix it.
 
 If you have a good magnifier, look over all the solder joints when the board is out and re-flow any that look suspect.

Here is another person with input problems, but different noise, good pictures is why I am adding it.
https://www.diyaudio.com/community/threads/fender-pr-241-repair-frontman-amp-made-in-mexico-high-pitch-sound.343735/

Good luck, and keep us informed of the results.
There are no stupid questions.
There are only stupid mistakes.

Roark