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Post subject: Re: 1967 Super Reverb: Ringing at about 3kHz when D chord pl
Posted: Wed Feb 05, 2014 2:01 pm
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OK:

Took chassis out of cabinet and tapped away and here's what I found:

There is a definite microphonic effect when I tap on pins 6&7 on preamp tubes #2 and #4 (looking from the right hand side of the tube chart and counting left).
The microphonic effect continues strongly if you tap the wires leading away from the tube pins, and even if you tap the phenolic above where the wires run, and also if I tap the large flat .02 MFd Mustard-colored capacitor...

Couldn't get any other strange sounds to emanate elsewhere, and I tapped everything except for under the cover where the main power electrolytics are located.)

Are we on to something here, or is this normal? Waiting in great anticipation!

Thanks in advance.


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Post subject: Re: 1967 Super Reverb: Ringing at about 3kHz when D chord pl
Posted: Wed Feb 05, 2014 2:15 pm
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Pictures of the wiring may help ;


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Post subject: Re: 1967 Super Reverb: Ringing at about 3kHz when D chord pl
Posted: Wed Feb 05, 2014 6:27 pm
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westeagle wrote:
OK:

if I tap the large flat .02 MFd Mustard-colored capacitor...

Thanks in advance.


Try this trick. Put a little dab of silicon sealer or glue gun goop on top of this cap. Now, listen to the amp. Has the frequency of the noise changed? Lower register? If so, it's the cap. Replace it.


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Post subject: Re: 1967 Super Reverb: Ringing at about 3kHz when D chord pl
Posted: Wed Feb 05, 2014 8:14 pm
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Image

Above is a link to a photo. I will also try the hot glue gun experiment. Thanks


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Post subject: Re: 1967 Super Reverb: Ringing at about 3kHz when D chord pl
Posted: Wed Feb 05, 2014 8:26 pm
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http://i31.photobucket.com/albums/c385/ ... 893424.jpg


Here's another photo


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Post subject: Re: 1967 Super Reverb: Ringing at about 3kHz when D chord pl
Posted: Thu Feb 06, 2014 2:31 am
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I'll do some wiring ,lead dress . I see a lots of bad wiring dress. I do that often in apms and you can hear it after the job.

1- Wires must cross over other at 90 degree and never be in parallel.
2- Wire must be as close $@! possible to the chassis.
3- Never run 2 wires close together.

. All this could induce some capacitance,


Look the pictures here to know what to do ;


viewtopic.php?f=12&t=92057&p=1038777#p1038777


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Post subject: Re: 1967 Super Reverb: Ringing at about 3kHz when D chord pl
Posted: Fri Feb 07, 2014 7:24 am
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To clarify, is it normal to hear some of the microphonic effect of tapping the wires and phenolic coming through the speakers?


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Post subject: Re: 1967 Super Reverb: Ringing at about 3kHz when D chord pl
Posted: Fri Feb 07, 2014 11:37 am
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westeagle wrote:
To clarify, is it normal to hear some of the microphonic effect of tapping the wires and phenolic coming through the speakers?


Yes on many wires or tubes it is normal . In some other no . Tapping will not help very much if you do not have any know how in electonic . Fix an amp by a amp forum , not easy .

Have you read my answer Feb 6 ?


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Post subject: Re: 1967 Super Reverb: Ringing at about 3kHz when D chord pl
Posted: Fri Feb 07, 2014 11:47 am
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Thanks

Yes I read your info on the wire specifics. Thank you. I will clean up that when I next have the amp apart.
-Just was wondering if I had a glaring problem because of the micro phonics.


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Post subject: Re: 1967 Super Reverb: Ringing at about 3kHz when D chord pl
Posted: Fri Feb 07, 2014 11:55 am
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westeagle wrote:
Thanks

-Just was wondering if I had a glaring problem because of the micro phonics.



A qualified tech will know


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Post subject: Re: 1967 Super Reverb: Ringing at about 3kHz when D chord pl
Posted: Sat Mar 15, 2014 6:14 am
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FOUND THE PROBLEM!

Early on in the trouble shooting process I tried an external speaker cabinet and it appeared that the problem didn't change. After spending $$ chasing this problem, and visiting a tech who said the amp sounded normal to him, I started from scratch again and tried a different external speaker, and voila, I noticed no killer "ice pick" resonance!
I then disconnected the original speakers in the amp and listened to them one by one: they all had the ice pick peak, when listened to individually.
I then ordered 2 new speakers: the Warehouse G10cs and G10C: to my surprise they actually sound fantastic -and no more icepick!!!! (I can now say I'm truly happy!!!)

Thanks to all who came up with suggestions earlier.


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Post subject: Re: 1967 Super Reverb: Ringing at about 3kHz when D chord pl
Posted: Sat Mar 15, 2014 8:15 am
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What type of speakers did you remove from the amp?

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: 1967 Super Reverb: Ringing at about 3kHz when D chord pl
Posted: Sat Mar 15, 2014 10:35 am
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stratele52 wrote:
westeagle wrote:
Thanks

-Just was wondering if I had a glaring problem because of the micro phonics.



A qualified tech will know



He was not qualifed or your amp sound/ speaker is a matter of taste ?


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Post subject: Re: 1967 Super Reverb: Ringing at about 3kHz when D chord pl
Posted: Wed Mar 19, 2014 8:48 am
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The Tech was certainly qualified (also a custom amp builder) with a very good reputation; but the sound my amp produces is apparently a matter of taste. To him it was the normal "bell" like tone of a blackface Super Reverb and he didn't find it annoying: To me that one frequency drilled right into my brain! Some people describe it as the "ice pick" sound, and it is really annoying to me.

The original code for all 4 speakers is "F412 67" I can't find a definite reference to which manufacturer it is though...


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Post subject: Re: 1967 Super Reverb: Ringing at about 3kHz when D chord pl
Posted: Wed Mar 19, 2014 9:12 am
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westeagle wrote:
The original code for all 4 speakers is "F412 67" I can't find a definite reference to which manufacturer it is though...


Not ringing any bells with me either.

Can you post a pic of one?

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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