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Post subject: 65 Twin Reverb Reissue Buzzing
Posted: Mon Mar 24, 2014 9:53 pm
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Hi, I have a fender twin reverb reissue that I am experiencing a buzzing issue with. I get a fairly loud buzzing coming from the amp whenever it is on. I've noticed that the buzzing intensifies when the reverb knob is turned up but the buzzing is present at all times even without an instrument plugged into the amp, turning up and down the volume doesn't seem to affect the loudness of the buzz. I've been researched and it seems that this might be a bad tube. I would like to make sure that that is indeed the problem, is there a way of isolating which tube could be causing this? Is it safe to pull tubes to find which is the culprit?

thank you!


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Post subject: Re: 65 Twin Reverb Reissue Buzzing
Posted: Mon Mar 24, 2014 10:25 pm
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The tubes responsible for the reverb circuit are V3 (driver) and V4 (recovery). Carefully study the tube chart within your amp's cabinet -- the tubes are numbered V1 through V10, from right to left. The amp should be switched completely off when replacing tubes and use only the same type/nomenclature of tubes in the designated sockets.

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: 65 Twin Reverb Reissue Buzzing
Posted: Mon Mar 24, 2014 11:03 pm
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Can I pull v3 and v4 to see if the buzzing goes away to make sure those are the ones to blame before i purchase replacements? Thanks for the response :)


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Post subject: Re: 65 Twin Reverb Reissue Buzzing
Posted: Mon Mar 24, 2014 11:15 pm
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Yes, that's what I would try.


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Post subject: Re: 65 Twin Reverb Reissue Buzzing
Posted: Mon Mar 24, 2014 11:25 pm
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well that was easier than I thought it would be. I pulled them and narrowed it down to v4 causing the buzzing. So now do I just need to replace the one tube or others as well? I also noticed that when I switch the stand by on I hear a rather loud popping noise, is this due to the bad tube? Thanks!


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Post subject: Re: 65 Twin Reverb Reissue Buzzing
Posted: Tue Mar 25, 2014 12:55 am
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The standby "pop" is likely unrelated to the buzzing issue.

Arjay

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Post subject: Re: 65 Twin Reverb Reissue Buzzing
Posted: Tue Mar 25, 2014 10:15 am
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is the pop an issue? what could be the cause of that?


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Post subject: Re: 65 Twin Reverb Reissue Buzzing
Posted: Tue Mar 25, 2014 10:55 am
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The standby switch may respond to contact cleaner. I like DeOxit DN5 or GN5. If not, you may need a new switch.

Good luck!


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Post subject: Re: 65 Twin Reverb Reissue Buzzing
Posted: Tue Mar 25, 2014 11:07 am
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thanks, I'll try some deoxit when I get home. I've read that some pop is normal, but it seems a little startling how loud it is.


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Post subject: Re: 65 Twin Reverb Reissue Buzzing
Posted: Tue Mar 25, 2014 3:02 pm
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The De-Oxit may help but contemporary switches are not built to the same standard of quality that the US-made Carling's were. If the contacts within the housing are worn or pitted no amount of cleaning solvent will restore the switch to totally silent operation.

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: 65 Twin Reverb Reissue Buzzing
Posted: Tue Mar 25, 2014 4:14 pm
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Arjay, very true. I have disassembled a US Carling or Switchcraft and lapped the contacts --- similar to what ppl used to do with old-school ignition points in a car. If you can get the contacts smooth and parallel to each other, the switch will work fine. Since no new toggle SPST is rated to 500VDC anymore --- go for the highest current rated one at 125 or 250VDC. Like a 15-amp switch.

http://www.ebay.com/itm/CARLING-TECHNOL ... 4897.l4276


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Post subject: Re: 65 Twin Reverb Reissue Buzzing
Posted: Mon Mar 31, 2014 7:14 pm
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So I ordered a replacement tube for v4 and popped it in and the issue didnt resolve :(. After some more diagnosing I've noticed that in both the reverb and clean channels, channel 1 is louder than channel 2. Also I dont think that dialing up the reverb necessarily makes the noise worse like i initially thought, I think it might just make it louder because the noise is then reverberating. Messing with the bass treble and mid changes the profile of the buzzing. Any additional recommendations of things I could try? Is it safe to assume that this is indeed a preamp tube issue because the buzzing gets louder with the volume?

to clarify the sound is like a very loud 60 cycle hum


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Post subject: Re: 65 Twin Reverb Reissue Buzzing
Posted: Tue Apr 01, 2014 12:20 am
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Sure it wasn't 120Hz? Makes it a big difference what is the source of the hum. 60Hz is below an open low E string. 120Hz is more like open A string.


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