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Post subject: Princeton 65 60 Cycle Hum
Posted: Sat Mar 04, 2017 7:04 pm
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I'm new to electric guitars. I picked up a Princeton 65, 2002 model, which was not working properly - it had a loud buzz, which I traced back to a damaged solder connection to a resistor. I soldered that back up. When I took the circuit board out, I noticed that the existing aluminum shielding on the amp case was damaged, and in some places frayed - so I removed it and replaced it with aluminum tape, to prevent any short occurring. The amp plays well - nice tone - all knobs working as they should, but there is 60 cycle hum.

The hum picks up in volume with the volume, treble, drive and reverb settings. I'm plugging directly from the guitar into the Princeton. I have a practice amp which has essentially no hum when my guitar is plugged into that, so I believe the hum is specific to the Princeton. I've posted a video to show the hum.

So two questions - is this hum normal for a Princeton amp? What would you suggest to fix it.

[youtube]https://youtu.be/FVhY83AhFlg[/youtube]


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Post subject: Re: Princeton 65 60 Cycle Hum
Posted: Sat Mar 04, 2017 10:14 pm
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You know, it sounds like 120Hz, not 60Hz. 60Hz is lower than open low E-chord. 120Hz is around open A-chord.

It makes a difference. 120Hz means bad PSU filtering or ground loop. 60Hz means bad heater line. Or heater hum is leaking into the signal. Usually, hum is PSU or ground related.


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Post subject: Re: Princeton 65 60 Cycle Hum
Posted: Sat Mar 04, 2017 11:29 pm
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BMW2002Ti wrote:
60Hz means bad heater line. Or heater hum is leaking into the signal.


The Princeton 65 is a solid-state amp, Steve.



Arjay

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Post subject: Re: Princeton 65 60 Cycle Hum
Posted: Sat Mar 04, 2017 11:38 pm
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Good lord! Time to have a mental health checkup. :lol:

I thought it was the '65 Princeton Reverb reissued amp. Maybe...


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Post subject: Re: Princeton 65 60 Cycle Hum
Posted: Sun Mar 05, 2017 3:45 am
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The amp was part of Fender's "Dyna Touch" lineup which included the Princeton Ultimate Chorus, the Deluxe 90, and the Stage 100/160 DSP models. They were the last of Fender's decent solid-state amps, good sounding and robustly built.

Arjay

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Post subject: Re: Princeton 65 60 Cycle Hum
Posted: Sun Mar 05, 2017 8:23 pm
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I take it that this hum isn't normal?


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Post subject: Re: Princeton 65 60 Cycle Hum
Posted: Sun Mar 05, 2017 8:51 pm
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No. Should be zero hum in a solid-state amplifier. Try cleaning input jacks with contact cleaner. May need to replace the main PSU filter caps = 2200mfd (C65 and 66) on right side of circuit board.

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Post subject: Re: Princeton 65 60 Cycle Hum
Posted: Sun Mar 05, 2017 10:41 pm
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If the hum did not manifest prior to the repairs you performed, you should retrace your steps and find something you missed -- a disconnected ground wire, a ribbon connector not fully seated, a cold solder joint, etc.

Arjay

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Post subject: Re: Princeton 65 60 Cycle Hum
Posted: Sun Aug 20, 2017 8:02 am
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Retroverbial wrote:
BMW2002Ti wrote:
60Hz means bad heater line. Or heater hum is leaking into the signal.


The Princeton 65 is a solid-state amp, Steve.



I have exactly the same amp; although I purchased mine in London circa 2003 IIRC. I also have the same problem with electrical hum; nothing plugged in, noise gets louder when plugging in a cable with or without a guitar attached (obviously worse without). Mine has never been opened up since I bought it. It has sat around for years with very low activity. I might follow your postings and try to repair it myself; thanks for posting this :-)

Arjay

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