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Post subject: Fender Custom 68 Princeton Reverb Hum
Posted: Wed Mar 09, 2016 9:39 am
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Hi guys, I've searched around and know there are quality control issues with these amps and some of you have had similar problems with humming and buzzing in brand new units. My issue is the reverb channel having a considerable amount of hum when turned up past 2. Reading up I see a lot of procedures suggested but it seems like once the problem is solved the post dies and what worked is not clearly stated.

I recently stopped by a guitar center and took a listen to a floor model and was shocked that the amp was dead quiet with reverb up to 10. Hitting the foot switch I couldn't hear a difference when turned on / off. So I received a replacement from Amazon but that unit also suffers from the same problem as well as a low level buzzing with everything at zero.

Here's what I tried:
- removing the reverb tank and swapping the cheap rca cable and placing the tank far away from the amp. The was a slight difference but very minimal.
- I swapped tubes around between the two amps and some combinations cleaned things up a tiny bit and some made it a bit worse.
- I tried every outlet in my apartment as well as lifting the ground with a plug adapter
- swapped reverb tanks between the two

This is all with no instrument plugged in

I'm a little frustrated as I love the sound of the amp but the hum is difficult to deal with when recording especially at lower volumes

Any help would be appreciated. I could try again with Amazon and replace with another unit and see if I get lucky or I may just return it and see if I can get a good unit off the floor from guitar center.

I really don't have any problem with the white noise from the tubes when the amp is cranked up, but the reverb hum is really irritating. I haven't owned any amps with tube driven reverb before so I'm not sure if it's just the way it goes or I just keep getting poorly manufactured units.

Anyone with a similar problem who found a fix and could help would be amazing. An audio clip of the same or similar fender amp with the reverb turned up would be very helpful as well so I have something to compare it to. I don't want to just feel like I'm being picky but the amp was expensive. Thanks!


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Post subject: Re: Fender Custom 68 Princeton Reverb Hum
Posted: Wed Mar 09, 2016 10:47 am
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My guess is the wiring layout is the main hum problem. Esp the wiring around the reverb driver and recovery tube sockets. And the layout of the heater lines to each socket.

IOW, inherent issue with all of these amps. A tech could try rearranging the wiring to see if this helps (maybe, this is what GC did to make their CPR so quiet). But, no guarantee of this fixing the amp's humming.

:(


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Post subject: Re: Fender Custom 68 Princeton Reverb Hum
Posted: Wed Mar 09, 2016 11:32 am
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Maybe you're right. I did find others though that said it took them 3 returns before they received an amp with no hum.

Wonder if guitar center would go through all that trouble with a floor model. I just stopped by again to test the same amp and it is for sure dead quiet. Even the volume all the way to 10 has less hiss than either of mine. I didn't check to see if they loaded it with better quality tubes.

I think I'll return both of mine back to amazon and just grab that floor model. They'll probably give me demo pricing and I don't mind if it's been played and broken in a bit. Hopefully it's just as quiet when i get it home and it's not a ground issue with my apartment's outlets. I do have them hooked up to a rack mount power conditioner though.


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Post subject: Re: Fender Custom 68 Princeton Reverb Hum
Posted: Wed Mar 09, 2016 11:45 am
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Esimonson718 wrote:
I think I'll return both of mine back to amazon and just grab that floor model.


A wise decision.

Purchasing a pig in a poke seldom results in satisfaction.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Fender Custom 68 Princeton Reverb Hum
Posted: Wed Mar 09, 2016 12:07 pm
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BMW2002Ti wrote:
My guess is the wiring layout is the main hum problem. Esp the wiring around the reverb driver and recovery tube sockets. And the layout of the heater lines to each socket.

IOW, inherent issue with all of these amps. A tech could try rearranging the wiring to see if this helps (maybe, this is what GC did to make their CPR so quiet). But, no guarantee of this fixing the amp's humming.

:(



It is not printed circuit those amps ? I don't know myself.


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Post subject: Re: Fender Custom 68 Princeton Reverb Hum
Posted: Wed Mar 09, 2016 12:50 pm
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stratele52 wrote:
BMW2002Ti wrote:
My guess is the wiring layout is the main hum problem. Esp the wiring around the reverb driver and recovery tube sockets. And the layout of the heater lines to each socket.

IOW, inherent issue with all of these amps. A tech could try rearranging the wiring to see if this helps (maybe, this is what GC did to make their CPR so quiet). But, no guarantee of this fixing the amp's humming.

:(



It is not printed circuit those amps ? I don't know myself.


I believe so but specs say the tube sockets are "hand-wired"...

IMAGE:
http://www.gitarrebass.musikmachen.de/M ... tomAmps-01


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Post subject: Re: Fender Custom 68 Princeton Reverb Hum
Posted: Wed Mar 09, 2016 1:30 pm
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Thank's for the photo. :)


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Post subject: Re: Fender Custom 68 Princeton Reverb Hum
Posted: Sat Nov 26, 2016 2:43 am
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I purchased mine in early 2014 and had a really bad issue with noise. It was clearly a lemon and I couldn't figure out why. One day, I read an article about opening up the reverb tank to make sure everything is ok. What I found were coils that were fixed to the housing in such a way that I couldn't help but to think that the assembler was new to his/her job, or simply wasn't happy and decided to take it out on the tank. I eventually dislodged the coils from the housing to allow them to 'float' as they're meant to and found that 90% of the noise went away.

Then there's the buzz from the enclosure. If I raise the volume to 4 and the bass any hire than 5 the buzz becomes unbearable. I simply look at the thing with disdain and even flip it a bird. I'm still looking into how to fix this on my own.

I must say: as a lifelong Fender devotee, I'm very disappointed about this amp and regret dishing out 1000 dollars for it. I've since purchased a similarly spec'd combo by a revived brand from an earlier era and haven't faced any issues. Much happier.


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Post subject: Re: Fender Custom 68 Princeton Reverb Hum
Posted: Tue Mar 05, 2019 4:44 am
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Hi
Just joined,my reason being that i wanted to share this fix for fender CPR 68 Reverb HUMMM..

I Found this on youtube - Troubleshooting:Fixing Fender Amp Spring Reverb Problem(Hum,Noise,Buzz).

I tried all the usual suspects..cables..tubes..tanks etc and this is the only thing that worked.
It noticeably reduced the hum when reverb was engaged.

The noise was still there but at a very low level but heres a strange discovery i made recently.

I tried one of my other amps for four days..during this time the CPR 68 was stored in a garage "mid winter"..

When i brought it indoors to use ALL reverb hum had gone!!!!

Gradually it came back to its normal low level?

Does anybody know what goes on...


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