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Post subject: '68 Super Reverb Noise
Posted: Tue Jun 24, 2014 4:27 pm
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Hi, this will be my first post.

I recently had my amp gone through with appeared to be a fine-toothed comb by a very talented amp tech. He brought me in a couple of times to voice the amp, whatever that means.

I should say that I'm a harp player, and also that the amp sounds wonderful since he did work on it. But I brought it in initially because it was making a noise when I played through it, a sort of "cloth-being-torn" sound that makes the thing unplayable.

Now, this guy knows his stuff, and at first the amp, like I said, sounded beautiful. But the noise has come back. I just can't believe that a technician of his standing could have missed something. So I'm asking if anyone here might have some idea of what could be causing this.

J


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Post subject: Re: '68 Super Reverb Noise
Posted: Tue Jun 24, 2014 4:39 pm
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Have you contacted the tech who last worked on the amp to voice your concern?

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: '68 Super Reverb Noise
Posted: Tue Jun 24, 2014 4:44 pm
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Retroverbial wrote:
Have you contacted the tech who last worked on the amp to voice your concern?

Arjay


Hi, Arjay. Oh, sure, he knows all about it. He's coming to my house soon, and I was sort of hoping I might find some suggestions here. The guy is so good, it's amazing to me that he couldn't find what's wrong.


Last edited by jnorem on Wed Jul 02, 2014 4:29 pm, edited 1 time in total.

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Post subject: Re: '68 Super Reverb Noise
Posted: Tue Jun 24, 2014 6:34 pm
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The symptom you've described seems to suggest random "motorboating", a malady common among older amps where one or more components has become microphonic with age. As such, the errant noise often manifests itself intermittently -- usually not within earshot of one's amp tech. Let him have the amp for several days so he can isolate the problem.

Arjay

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Post subject: Re: '68 Super Reverb Noise
Posted: Tue Jun 24, 2014 8:21 pm
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Retroverbial wrote:
The symptom you've described seems to suggest random "motorboating", a malady common among older amps where one or more components has become microphonic with age. As such, the errant noise often manifests itself intermittently -- usually not within earshot of one's amp tech. Let him have the amp for several days so he can isolate the problem.

Arjay


Can you talk about what microphonic means? Is it something a good tech would understand?


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Post subject: Re: '68 Super Reverb Noise
Posted: Wed Jun 25, 2014 2:07 am
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jnorem wrote:
[

. The guy is so good, it's amazing to me that he couldn't find what's wrong.



Sorry but it is not so good , noise is mostly easy to find for a qualified tech


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Post subject: Re: '68 Super Reverb Noise
Posted: Wed Jun 25, 2014 7:00 am
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jnorem wrote:
Hi, this will be my first post.

It was making a noise when I played through it, a sort of "cloth-being-torn" sound that makes the thing unplayable.

Now, this guy knows his stuff, and at first the amp, like I said, sounded beautiful. But the noise has come back. I just can't believe that a technician of his standing could have missed something. So I'm asking if anyone here might have some idea of what could be causing this.

J


jnorem, Welcome to the Forum. :D

Offhand, the description sounds like it maybe either tube rush noise --- which is usually related to a signal tube (12AX7 or 12AT7). Or maybe oddball overtones --- due to inadequate main power supply filtering (main filter caps). Poor filtering in the main PSU can cause "motorboating," too.

Did this tech replace the main PSU filtering caps?

As for tube rush, try cleaning the pins and sockets of all of the 12AX7 and 12AT7 positions with good contact cleaner. I like Caig Deoxit GN5. Work the tubes in-and-out of each socket a couple of times. Hopefully, this will help. If not (and the main filter caps are ok), you may need new tube(s) and tighten some sockets.

Keep us posted. Good luck! :mrgreen:


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Post subject: Re: '68 Super Reverb Noise
Posted: Wed Jun 25, 2014 11:38 am
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Thanks for the suggestions, guys. I'm pasting them all into one document to print for the guy when he comes over.

J


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Post subject: Re: '68 Super Reverb Noise
Posted: Wed Jun 25, 2014 11:47 am
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jnorem wrote:
Can you talk about what microphonic means? Is it something a good tech would understand?


If your tech doesn't know the term and how to troubleshoot and isolate the cause, it's time to find a new tech.

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: '68 Super Reverb Noise
Posted: Wed Jun 25, 2014 1:06 pm
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Retroverbial wrote:
jnorem wrote:
Can you talk about what microphonic means? Is it something a good tech would understand?


If your tech doesn't know the term and how to troubleshoot and isolate the cause, it's time to find a new tech.

Arjay


Good point.


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