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Topic: High pitched hum in Deluxe question |
Ken Metcalf
From:
San Antonio Texas USA
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Posted 20 Jan 2011 7:08 am |
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I have a Fender deluxe mid 70s that has developed a very high pitched constant ring or hum.
It is so high pitched that it is almost like only dogs or people with out hearing loss can hear it.
It gets louder when the vol. is turned up or boosted and is definitely in the amp.
I think the tubes are okay but am wondering what you guys might think before it goes to the shop.
Thanks
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MSA 12 String E9th/B6th Universal.
Little Walter PF-89.
Bunch of stomp boxes |
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Tim Marcus
From:
San Francisco, CA
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Posted 20 Jan 2011 5:11 pm
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first thing I would do is try and isolate the hum by pulling out preamp/inverter tubes one by one. Mid 70's Fenders are wired like a shotgun went off at a pasta shop - so it could be some parasitic oscillation caused by components slowly going out of tolerance over the years and bad wiring. Other culprits could be RF getting in through a bad cap or resistor.
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Milkmansound.com |
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Blake Hawkins
From:
Florida
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Posted 20 Jan 2011 7:05 pm
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What Tim said. You might also check the bypass caps.
An aging filter can cause the same problem. The test for that is to connect a .1 mfd, 600 volt cap across the filter. If it is the filter the noise will be gone.
Blake |
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Ken Metcalf
From:
San Antonio Texas USA
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Posted 21 Jan 2011 7:43 am
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Thanks you guys ...
Sounds like a trip the amp shop to me.
as I am not a re-cap type of guy.
Always wanted to though.
_________________
MSA 12 String E9th/B6th Universal.
Little Walter PF-89.
Bunch of stomp boxes |
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Rick Kreuziger
From:
Merrillan, Wisconsin
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Posted 21 Jan 2011 1:21 pm
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[quote=Mid 70's Fenders are wired like a shotgun went off at a pasta shop -[/quote]
 Now that's funny...  |
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Rich Hlaves
From:
Wildomar, California, USA
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Posted 21 Jan 2011 3:02 pm
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| Rick Kreuziger wrote: |
| [quote=Mid 70's Fenders are wired like a shotgun went off at a pasta shop - |
Now that's funny... [/quote]
True too. Some of them are a real mess.
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On man....let the smoke out of another one. |
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Blake Hawkins
From:
Florida
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Posted 21 Jan 2011 6:32 pm
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If you think a Fender Amp is wired badly....
just look inside of a Gibson. |
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Tony Prior
From:
Charlotte NC
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Posted 22 Jan 2011 3:54 am
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well I would not agree that mid 70's or later Fender amps are wired poorly, I have a 78 PR and a 76 DR, both are very nice, very clean, well assembled and the workmanship is just fine. They are still using the carbon bds wired to the off bd components.
Now, that does not mean there may be a bad solder joint or a faulty component/connection, it may very well be the case. Bad grounds, bad tube socket etc can easily cause this type of noise. but someone has to look it over.
To me, the first place to always start is with the Pre-amp tubes, as that is the easiest place to start and requires no tools, just KNOWN GOOD tubes, note I didn't say NEW tubes.
Taking the chassis out and determining the source of the noise/hum is best left to a tech that has Fender chassis experience. I happen to feel that Fender amps ( of the era) are fairly easy to find the cause of trouble and repair. Don't give up on it, it is a fine amp and being over 30 years old is typical of a repair of this sort.
t
_________________
Emmons L-II , Fender Telecasters, B-Benders , Eastman Mandolin ,
Pro Tools 12 on WIN 7 !
jobless- but not homeless- now retired 9 years
CURRENT MUSIC TRACKS AT > https://tprior2241.wixsite.com/website |
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Ken Fox
From:
Nashville GA USA
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Posted 22 Jan 2011 6:02 pm
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| Does the noise go away when the reverb control is turned off? |
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John Billings
From:
Ohio, USA
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Posted 23 Jan 2011 4:30 am
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| Microphonic preamp tube? Tap them with a pencil's eraser end. |
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Derrell Stephens
From:
Shreveport, La. USA
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Posted 2 Feb 2011 7:38 pm
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Ken is most probably on the right track ... likely a pull up Ecap if not a tube ... been there.
D |
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Ken Metcalf
From:
San Antonio Texas USA
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Posted 3 Feb 2011 7:10 am
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Doesn't change when the reverb is turned down and does not make noise if I thump the tubes.
It is down at Acosta Music in San Antonio (Good Guys).
I will post when they tell me.
This is a really high frequency sound.
_________________
MSA 12 String E9th/B6th Universal.
Little Walter PF-89.
Bunch of stomp boxes |
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Ken Fox
From:
Nashville GA USA
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Posted 3 Feb 2011 12:01 pm
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The 20uf filter caps also prevent interstage coupling, that may well be the issue. When one of those open it will can squeel like pig!
I also had a Peavey Triumph 60 with Chinese preamp tubes that would feedback. Put good tubes in and fixed that one! |
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