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Post subject: Fender Princeton 650 Troubleshooting help
Posted: Sat Jan 02, 2016 12:28 pm
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Hey all!

Out of a deal i got a Fender Princeton amp for free with 2 things i'd love to repair myself. I studied Elektromechanical Engineering and made some fuzz pedals so i know something but i never repaired a Guitar Amp before so that's pretty new to me.

There are 2 problems with the amp:

1) When turning on, without guitar cable in it, there is a huge humm sound of the transformer i guess, untill i put in a guitar cable, then it stops.


2) This is the major problem i need to fix if i wanna use the amp: When playing there is a huge buzzing/cracking noise, i already tested another speaker so that should not be the problem, i made a recording: https://dl.dropboxusercontent.com/u/167 ... opname.mp3
Could someone get me started on looking where the problem may be?

Thanks alot!
David


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Post subject: Re: Fender Princeton 650 Troubleshooting help
Posted: Sat Jan 02, 2016 1:44 pm
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davidof wrote:
Hey all!

Out of a deal i got a Fender Princeton amp for free with 2 things i'd love to repair myself. I studied Elektromechanical Engineering and made some fuzz pedals so i know something but i never repaired a Guitar Amp before so that's pretty new to me.

There are 2 problems with the amp:

1) When turning on, without guitar cable in it, there is a huge humm sound of the transformer i guess, untill i put in a guitar cable, then it stops.

Check input jacks shorting contact .
Each input jack have a normaly close contact ( connect to ground ) to stop noise when nothing plug . If the are dirty , rusty or open you ear noise.
If you plug guitar , the guitar itself is a resistor to ground , this stop the noise from a broken jack


2) This is the major problem i need to fix if i wanna use the amp: When playing there is a huge buzzing/cracking noise, i already tested another speaker so that should not be the problem, i made a recording: https://dl.dropboxusercontent.com/u/167 ... opname.mp3
Could someone get me started on looking where the problem may be?

Bad solder , dirty tubes pins and socket ; contact cleaner and unplug plug few times.
Check output tubes defect or bias too hot
Check 12XX7 tubes.


Thanks alot!
David


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Post subject: Re: Fender Princeton 650 Troubleshooting help
Posted: Sat Jan 02, 2016 5:15 pm
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The
stratele52 wrote:
davidof wrote:
Hey all!

Out of a deal i got a Fender Princeton amp for free with 2 things i'd love to repair myself. I studied Elektromechanical Engineering and made some fuzz pedals so i know something but i never repaired a Guitar Amp before so that's pretty new to me.

There are 2 problems with the amp:

1) When turning on, without guitar cable in it, there is a huge humm sound of the transformer i guess, untill i put in a guitar cable, then it stops.

Check input jacks shorting contact .
Each input jack have a normaly close contact ( connect to ground ) to stop noise when nothing plug . If the are dirty , rusty or open you ear noise.
If you plug guitar , the guitar itself is a resistor to ground , this stop the noise from a broken jack


2) This is the major problem i need to fix if i wanna use the amp: When playing there is a huge buzzing/cracking noise, i already tested another speaker so that should not be the problem, i made a recording: https://dl.dropboxusercontent.com/u/167 ... opname.mp3
Could someone get me started on looking where the problem may be?

Bad solder , dirty tubes pins and socket ; contact cleaner and unplug plug few times.
Check output tubes defect or bias too hot
Check 12XX7 tubes.


Thanks alot!
David


The Princeton 650 is a Solid state amp, no tubes :)


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Post subject: Re: Fender Princeton 650 Troubleshooting help
Posted: Sat Jan 02, 2016 5:16 pm
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stratele52 wrote:
davidof wrote:
Hey all!

Out of a deal i got a Fender Princeton amp for free with 2 things i'd love to repair myself. I studied Elektromechanical Engineering and made some fuzz pedals so i know something but i never repaired a Guitar Amp before so that's pretty new to me.

There are 2 problems with the amp:

1) When turning on, without guitar cable in it, there is a huge humm sound of the transformer i guess, untill i put in a guitar cable, then it stops.

Check input jacks shorting contact .
Each input jack have a normaly close contact ( connect to ground ) to stop noise when nothing plug . If the are dirty , rusty or open you ear noise.
If you plug guitar , the guitar itself is a resistor to ground , this stop the noise from a broken jack


2) This is the major problem i need to fix if i wanna use the amp: When playing there is a huge buzzing/cracking noise, i already tested another speaker so that should not be the problem, i made a recording: https://dl.dropboxusercontent.com/u/167 ... opname.mp3
Could someone get me started on looking where the problem may be?

Bad solder , dirty tubes pins and socket ; contact cleaner and unplug plug few times.
Check output tubes defect or bias too hot
Check 12XX7 tubes.


Thanks alot!
David

"stratele52"; The Princeton 650 is a solid state amp.
EDIT: davidof types faster than I! :lol:

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Post subject: Re: Fender Princeton 650 Troubleshooting help
Posted: Sat Jan 02, 2016 5:38 pm
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Solid states ;

Ok input jacks are same. Check contact to ground

Check solders , check and clean all connection , ribon wire.
Check power supply's broken solder , burn resistors

Schematic here ;
http://support.fender.com/schematics/gu ... ematic.pdf


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Post subject: Re: Fender Princeton 650 Troubleshooting help
Posted: Sun Jan 03, 2016 3:24 am
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Should i take out the print? To check the other side?


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Post subject: Re: Fender Princeton 650 Troubleshooting help
Posted: Sun Jan 03, 2016 3:32 am
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davidof wrote:
Should i take out the print? To check the other side?


Yes for solders,

You can start by cleaning ribbon wire connectors first and look at the amp carefully if you see any burns and try amp.

If not better ,look at the back to see printed circuit side if some broken solder . This may nee some experience to know if solder are bad or not , not easy ...
Or you reheat them.


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Post subject: Re: Fender Princeton 650 Troubleshooting help
Posted: Sun Jan 03, 2016 1:11 pm
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stratele52 wrote:
davidof wrote:
Should i take out the print? To check the other side?


Yes for solders,

You can start by cleaning ribbon wire connectors first and look at the amp carefully if you see any burns and try amp.

If not better ,look at the back to see printed circuit side if some broken solder . This may nee some experience to know if solder are bad or not , not easy ...
Or you reheat them.


Can solders really get bad just by themselves?


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Post subject: Re: Fender Princeton 650 Troubleshooting help
Posted: Sun Jan 03, 2016 1:18 pm
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Yes , today they put minimum solder ($$) and the new lead free solder are "fragile ".


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Post subject: Re: Fender Princeton 650 Troubleshooting help
Posted: Sun Jan 03, 2016 3:56 pm
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davidof wrote:
Can solders really get bad just by themselves?


Some of the chicom-made stuff is so shoddily assembled that it never even survives the boat ride across the puddle in a container ship.

:roll:

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 Princeton 650 Troubleshooting help
Posted: Mon Jan 04, 2016 4:03 am
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Retroverbial wrote:
davidof wrote:
Can solders really get bad just by themselves?


Some of the chicom-made stuff is so shoddily assembled that it never even survives the boat ride across the puddle in a container ship.

:roll:


Arjay


+1


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