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Post subject: Pro Junior - screaming noise after power up - bad tubes?
Posted: Sun Jul 19, 2009 12:54 pm
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Hi all, I have a Fender Pro Junior that I recently acquired used a couple months ago. It's worked fine until a couple days ago, when it started making uncontrollable, buzzing/screeching noises about thirty seconds after powering up. It does this whether a guitar is plugged in or not, and the noise is unaffected by the volume knob. I've tried it plugged into an external speaker - same thing. After the initial noise subsides, the tone is very weak with lots of white noise. I'm wondering if someone can help me isolate this problem; I have no idea how old the tubes are but I wouldn't be surprised if they're the original ones. Could a bad preamp tube be causing this? The noise is loud as hell so I'm guessing the power tubes are ok. Any help here would be appreciated. Thanks!

Note: I just tapped all of the tubes and got a popping noise from one of my power tubes. It's definitely dead... has anyone had issues with weird noises/amp generally acting crazy because of a dead power tube? I'm thinking it might be best just to retube the entire amp.


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Post subject: Re: Pro Junior - screaming noise after power up - bad tubes?
Posted: Sun Jul 19, 2009 11:31 pm
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muscles marinara wrote:
Hi all, I have a Fender Pro Junior that I recently acquired used a couple months ago. It's worked fine until a couple days ago, when it started making uncontrollable, buzzing/screeching noises about thirty seconds after powering up. It does this whether a guitar is plugged in or not, and the noise is unaffected by the volume knob. I've tried it plugged into an external speaker - same thing. After the initial noise subsides, the tone is very weak with lots of white noise. I'm wondering if someone can help me isolate this problem; I have no idea how old the tubes are but I wouldn't be surprised if they're the original ones. Could a bad preamp tube be causing this? The noise is loud as hell so I'm guessing the power tubes are ok. Any help here would be appreciated. Thanks!

Note: I just tapped all of the tubes and got a popping noise from one of my power tubes. It's definitely dead... has anyone had issues with weird noises/amp generally acting crazy because of a dead power tube? I'm thinking it might be best just to retube the entire amp.


I've got a PJ and it's never done anything remotely similar to what you describe. The easiest and cheapest remedy for tube amps is a change of tubes. Buy a new set (they're worth having around regardless) and change them one at a time, playing the amp after each change. This should isolate the bad tube(s) and let you replace them.

If it continues, it's beyond my simple knowledge. Opinions, anyone?


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Posted: Sun Jul 19, 2009 11:37 pm
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I had the same thing happen to me with a Peavey Classic 20 I had. I replaced all the tubes and the amp went back to normal.

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Posted: Mon Jul 20, 2009 8:32 am
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Last edited by billco on Sat Dec 11, 2010 5:08 pm, edited 1 time in total.

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Posted: Mon Jul 20, 2009 4:22 pm
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Thanks for the help, CAFeathers, Billco and Vulkan; this was a pawn shop purchase and I was debating retubing the amp as soon as I got it; I just ordered new preamp and output tubes, so hopefully this will solve the problem. Again, thanks for the help... especially the model-specific info, I appreciate it. Will update as soon as I retube the amp.


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Posted: Mon Jul 20, 2009 11:22 pm
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muscles marinara wrote:
Thanks for the help, CAFeathers, Billco and Vulkan; this was a pawn shop purchase and I was debating retubing the amp as soon as I got it; I just ordered new preamp and output tubes, so hopefully this will solve the problem. Again, thanks for the help... especially the model-specific info, I appreciate it. Will update as soon as I retube the amp.


Even though you've already ordered tubes, I think it's my civic duty as a fellow PJ'er to recommend Tung-Sol 12ax7s. They are cheaper than JJs, more readily available, and sound very, very good.


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Posted: Tue Jul 21, 2009 2:36 pm
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Vulkan wrote:
muscles marinara wrote:
Thanks for the help, CAFeathers, Billco and Vulkan; this was a pawn shop purchase and I was debating retubing the amp as soon as I got it; I just ordered new preamp and output tubes, so hopefully this will solve the problem. Again, thanks for the help... especially the model-specific info, I appreciate it. Will update as soon as I retube the amp.


Even though you've already ordered tubes, I think it's my civic duty as a fellow PJ'er to recommend Tung-Sol 12ax7s. They are cheaper than JJs, more readily available, and sound very, very good.


Duly noted... I'll give those a try next time; I work this little amp pretty hard so that opportunity might come relatively soon, hopefully not too soon though. Thanks for the tip.


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Posted: Wed Jul 22, 2009 9:49 am
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muscles marinara wrote:
Vulkan wrote:
muscles marinara wrote:
Thanks for the help, CAFeathers, Billco and Vulkan; this was a pawn shop purchase and I was debating retubing the amp as soon as I got it; I just ordered new preamp and output tubes, so hopefully this will solve the problem. Again, thanks for the help... especially the model-specific info, I appreciate it. Will update as soon as I retube the amp.


Even though you've already ordered tubes, I think it's my civic duty as a fellow PJ'er to recommend Tung-Sol 12ax7s. They are cheaper than JJs, more readily available, and sound very, very good.


Duly noted... I'll give those a try next time; I work this little amp pretty hard so that opportunity might come relatively soon, hopefully not too soon though. Thanks for the tip.


That's what PJs are made for, my friend: working hard! I remember one jam session where I had the thing running hot for almost five hours. It was still warm an hour later!


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Posted: Thu Jul 23, 2009 8:50 pm
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Retubed the PJ today, problem solved... man this baby is loud! Thanks for the help, guys.


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