New member with Fender amp questions

[Doc74]

Hi everyone, I recently bought a mid 90's Fender Princeton Chorus and while it works like a charm, it does have some background noise which I would like to see gone.

When I disconnect the guitar cable i can crank the volume, both clean and overdrive and it'll give me very little noise, nothing to get concerned about.
Onc eI plug the cable in it gets hissy and it gets lous when I crank it, especially on overdrive.

What should I check to solve this problem?  Can it be a bad ground somewhere?
Is it dangerous to take the amp apart or is it safe as long as it's unplugged?

I'm not sure where to start here so any advice is welcome and appreciated.

Thanks!

[syndromet]

Hi, and welcome. High quality cables and shielded, well grounded guitars is where I would start. Since the amp is silent when unplugged, there is probably nothing wrong with the amp.

[Doc74]

Thanks for the reply and the welcome!

I have two cheap and long cables and one very short pedal cable and it all sounds the same. 
Should I get like a monster or Dimarzio cable?

I tried both my electric and aocustic/electric guitar and it's the same background noise.
My electric does have a ground problem I can't seem to locate, it has a sligth buzz that goes away when I touch the hardware or strings.

I thought maybe the input jack on the amp had some issues or there could be a bad solder or something.  It was owned by an older guy who took very good care of it but it had been sitting unused for many years.

I read something a while back on making a permanent ground on an amp but I forgot where.  Is this something that could improve matters?

[nashvillebill]

I have an early 90's Princeton Chorus and it's very quiet, whether with my electric or my acoustic/electric.  I agree with syndromet, I doubt it's an amp problem since there's no noise unless the guitars are plugged in. 

What guitars are you using?  Some guitars are shielded better or worse than others, and also single coil guitars (like Strats) can be very noisy.  You may also have something around the house that's emitting radio-frequency noise that's being picked up by the guitars (a ceiling fan, a refrigerator, etc).  Finally, pedals can be very noisy.

IMHO, a decent quality shielded guitar cable should work fine, there's no need to buy a $50 cable.  Get some new $15 guitar cables from American Musical, Musicians Friend, or Parts Express....you ARE using guitar (instrument) cables, I hope?  Speaker cables (with two unshielded wires side-by-side, commonly called zip cord)  are a no-no, they will pick up noise badly!!!

My amp has a grounded (3-prong) power plug, for safety's sake I hope yours still has the 3rd plug.   If the amp is quiet unplugged, though, the amp grounding isn't an issue IMO.

[Doc74]

Yep it has the 3 prong.  I am using guitar cables but they were cheap.  On the other hand when I use either guitars with my acoustic Behringer 15W amp, I get no noise, unless I really crank it.  But at low volume the Behrionger is a lot less noisy than the Fender at the same low volume.

I also tried just plugging in a guitar cable without plugging the other end in the guitar.  I put the unplugged end on the bed and was careful not to touch it, the noise is the same.

My electric is a Gretsch hollow body but I swapped the original humbuckers.  It has a single coil GFS in the neck position and a humbucker GFS in the bridge.  Again it's very quiet with the Behringer.
The acoustic/electric is a Carlo Robelli, same story on both amps.

The Fender is just noisy so it seems there's a problem somewhere.  I'll try out a few different outlets in different rooms to see if there's any change.

When I recently tried to lengthen the pup wires in the Gretsch and put in some shielded wire I must have done something wrong now I have a buzz in it that goes away when touching the hardware or strings but it doesn't seem to have anything to do with the noise coming from the amp.

I really love the way the PC sounds but as it is I have to play through the Behringer, the noise from the PC is too distracting.

The footswitch does have that side by side wire cable but I thought it was the original.  Unplugging the switch doesn't change the noise though.
I sure hope I can get rid of the noise...

[joecool85]

Sounds to me like a dirty/worn out input jack.  You can get contact cleaner and try that, if that doesn't solve it, replacing a jack is pretty simple and should solve your issue.

[Doc74]

Cool, so I'll have to take the amp apart.  Anything I need to watch out for?  Anything in there than can zap my shoes off even after I unplug the thing?

I forgot to mention, it has two input jacks.  One high and one low impedance input, both make the same noise.  Could it be coincidence or are they somehow connected somewhere?

[Doc74]

Altough it makes a lot more noise when there's a cable plugged into one of the jacks, the amp does make a hissing noise when nothing's plugged in.  It just doesn't change when I turn the knobs.  At any volume, clean or overdriven channel it makes the same hiss.  Only when I plug a cable in does it get louder when I turn up eiother volume.  On the overdrive channel it's really loud with the gain up.  Loud enough to take all the fun out of playing.

I tried my little Behringer amp again and it too has this hiss without anything plugged in, it's just less because it's so small.

I lugged the Fender around the house and tried a bunch of different outlets, no change, the hiss remains.

Oh and when the guitar's plugged in and I turn off the amp, it gives me a loud hiss before it shuts off. Wth???

Do I have a ground problem in the outlets?  There's a stick outside in the ground but how effective it is I don't know.  How can I test if the outlets are properly grounded?

Got a buzz in the guitar, hiss in the amp...should've stuck with the saxophone....

[Doc74]

Update

I must have tested the amp while the furnace was running and making noise.
Altough not nearly as loud as with a cable in the input jack, the amp does have a buzzing noise with nothing plugged in.
It's not overly loud but clearly audible,  It does not change with turning the dials.

Plugging in a cable ads the white noise that's affected by turning the dials.

Could it be that the filter caps are shot?  If so where can I find some and how do I replace them?

I also tested the wall outlets in my house with one of those little testers you plug in a nd get a reading fom the lights.
The all seem to be in order but I did read on the package that it won't detect a faulty ground....great help that gizmo was...

How can I find out if the ground is ok?

Thanks for reading!

[nashvillebill]

The buzz sure sounds like a filter cap.  I have read that the Princeton and Ultimate Chorus amps both share a common problem:  the large filter caps are prone to vibration-induced problems.  Check the solder joints on the caps, make sure the traces haven't cracked, make sure the leads haven't broken going into the cap....

I used a hot glue gun to secure the caps more securely on mine, I've done this on all my bass amps.

[Doc74]

Thanks nashvillebill, I'll give it a look.