FDP Home Page / FDP Forum / FAQ's

The FDP is made possible by the following companies and individual members like you.
Please use the links below to show them we value their sponsorship.

MOD KITS DIY

Apex Tube Matching

Sweetwater

Antique Electronics Supply

Advertise here

Yellowjackets Tube Converters

Jensen Loudspeakers

WD Music

Guitar Center

Musician's Friend

Amplified Parts


* God bless America and our men and women in uniform *

* Illegitimi non carborundum! *

If you benefit and learn from the FDP and enjoy our site, please help support us and become a Contributing Member or make a Donation today! The FDP counts on YOU to help keep the site going with an annual contribution. It's quick and easy with PayPal. Please do it TODAY!

Chris Greene, Host & Founder

LOST YOUR PASSWORD?

......................................................................

   
FDP Jam
Calendar
Find musicians
in your area!
  Search the Forums  

FDP Forum / Fender Amps: Vintage (before 1985) / What's wrong with my '73 Princeton Reverb?

BbendFender
Contributing Member
**********
***

American Patriot

About as ordinary as you can get.
Jul 15th, 2018 05:48 PM   Edit   Profile  

Played a gig Fri. night and no problem with the amp. Had another gig Sat. night and plugged in the amp, using a Variac set to 117v. Verified the Variac with mulitmeter at 117v.
Immediately on warm up, the amp had a loud hum. No controls would stop the hum. Checked all tubes (changed) and same results. I haven't checked out the amp since I got home. Nothing I did had an effect on the loud hum.
Anybody have anything right off the bat. This is my main gigging amp and I've never had a problem with it.

BbendFender
Contributing Member
**********
***

American Patriot

About as ordinary as you can get.
Jul 15th, 2018 05:50 PM   Edit   Profile  

Well heck, I just noticed another thread about a Princeton with hum. I'll check the filter cap but this amp has been serviced within the last 4 years with total cap job. It has been flawless until now.

Leftee
Contributing Member
**********
**********
********

VA

Jul 15th, 2018 06:15 PM   Edit   Profile  

Gigs at the same venue?

BbendFender
Contributing Member
**********
***

American Patriot

About as ordinary as you can get.
Jul 15th, 2018 06:51 PM   Edit   Profile  

No, 2 different places. Never had any electrical problems at either place. I always check the power with my voltmeter to make sure of what we have. I also use a Variac and set my power at 117-120v. We have 124v at my house.

Leftee
Contributing Member
**********
**********
********

VA

Jul 15th, 2018 07:55 PM   Edit   Profile  

Fire it up at home and see what you have first. I’m wondering if there was a grounding issue at the second venue.

willie

Too Near Atlanta GA

Amp Tech Emeritus
Jul 15th, 2018 08:02 PM   Edit   Profile  

Not all that unusual to have a cap failure after a recent cap job due to either a component failure or even more commonly a solder flaw on a recently installed cap. If the volume doesn't change the intensity of the hum, it is most likely due to a cap failure of some kind.

willie

BbendFender
Contributing Member
**********
***

American Patriot

About as ordinary as you can get.
Jul 15th, 2018 08:21 PM   Edit   Profile  

Thanks guys. I'll take a look at it tomorrow.

BbendFender
Contributing Member
**********
***

American Patriot

About as ordinary as you can get.
Jul 16th, 2018 12:00 PM   Edit   Profile  

Bad can cap. Replaced it and it works now.

Leftee
Contributing Member
**********
**********
********

VA

Jul 16th, 2018 01:36 PM   Edit   Profile  

Thumbs up!

Caps ain’t what they used to be.

BbendFender
Contributing Member
**********
***

American Patriot

About as ordinary as you can get.
Jul 16th, 2018 05:26 PM   Edit   Profile  

No they're not Leftee. First one lasted 40 years and next one just a few years.
This is a great amp.

willie

Too Near Atlanta GA

Amp Tech Emeritus
Jul 18th, 2018 02:08 PM   Edit   Profile  

Exactly...again, a fairly common occurrence. Multi section cap cans, while expensive just aren't all that great these days. Glad you got it fixed.

w

Leftee
Contributing Member
**********
**********
********

VA

Jul 18th, 2018 02:23 PM   Edit   Profile  

Several years ago I was converting old PA amps into guitar amps. I’d build a cap board to replace the cap can(s).

willie

Too Near Atlanta GA

Amp Tech Emeritus
Jul 20th, 2018 12:01 PM   Edit   Profile  

The available "CE" and JJ cans are not all that bad, just not as good as the old Sprague, Mallory, etc... made in USA types we used to get in the much lamented "good old days". :)

w

Peegoo
Contributing Member
**********
**********
**********
*

Ooo that sandwich

is gonna get et
Jul 22nd, 2018 12:13 PM   Edit   Profile  

Good outcome!

Willie, you're like the country doctors from old westerns: look at a sick man or a lame horse, and instantly know what the problem is.

Te 52

Laws of Physics

strictly enforced
Jul 22nd, 2018 01:36 PM   Edit   Profile  

Yeah, willie is the "Amp Whisperer."

BbendFender
Contributing Member
**********
***

American Patriot

About as ordinary as you can get.
Jul 22nd, 2018 06:34 PM   Edit   Profile  

This little Princeton Reverb is running great. I did make the mistake of leaving it on all night the other night but it didn't hurt a thing. No more hum and it sounds great.

Silverface

Lawndale CA

No Chops but Great Tone ©
Sep 7th, 2018 10:03 PM   Edit   Profile  

FWIW a Variac is not recommended for maintaining stable voltage over a period of time - it's test tool and is not meant for "set and forget" uses like a power strip. They can drift, be bumped and don't do a thing for you if there's a power spike.

For gig purposes a real voltage regulator with spike protection would be recommended - but only if you play gigs where they supply temporary power from generators or with obviously haphazard wiring.

A $7 outlet tester so you know whether the ground is actually connected and the polarity correct is FAR more useful than a Variac (I check the power source every place I play)

Your amp doesn't need a "not to exceed" level of 117 or whatever - it serves no purpose, but a Variac is potentially more harmful than helpful.

Modern wall voltage that hits 121 or so is perfectly safe for any vintage tube amp - BF, SF, tweeds - doesn't matter. The only differences are in the test voltages on the schematic - they need to be factored for actual supply voltage.

FDP Forum / Fender Amps: Vintage (before 1985) / What's wrong with my '73 Princeton Reverb?




Reply to this Topic
Display my email address             Lost your password?
Your Message:
Link Address (URL):
Link Title:




Moderators: Chris Greene  Iron Man  reverendrob  

FDP, LLC Privacy Policy: Your real name, username, and email
are held in confidence and not disclosed to any third parties, sold, or
used for anything other than FDP Forum registration unless you specifically authorize disclosure.

Furtkamp.com 
Internet Application Development

Copyright © 1999-2018 Fender Discussion Page, LLC   All Rights Reserved