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Topic: Fender Vibrosonic noise |
Ken Metcalf
From:
San Antonio Texas USA
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Posted 23 Jan 2008 3:32 pm |
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Fender Vibrosonic noise,
My Vibro started to make a weird reverb sound, sort of a random odd differing sounds not related to bumping or vibration, but kind of sounds like that.
When I turn the volume down, off or up it stays at the same level even when vol is off.
Even with no cords, guitars etc. plugged in still makes weird sounds.
Any one have a clue or experience with this ??
Thanks
Kenny
_________________
MSA 12 String E9th/B6th Universal.
Little Walter PF-89.
Bunch of stomp boxes |
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Donny Hinson
From:
Glen Burnie, Md. U.S.A.
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Posted 23 Jan 2008 3:45 pm
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Spray some cleaner into the controls (reverb and volume, primarily) and report back.  |
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Marvin Born
From:
Ohio, USA
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Posted 23 Jan 2008 7:50 pm Reverb
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Does the noise sound like reverbed static?
Swap the 12AX7 tubes around, ( keep track of where they go) and see if the problem moves. Or replace the tubes one at a time. If it is static, sometimes the " plate load" resistor in the reverb tube gets noisey and must be replaced. If you don't know how to work on tube amps see a good tech. |
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Ken Metcalf
From:
San Antonio Texas USA
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Posted 24 Jan 2008 11:04 am
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It sounds like the Boing Boing sound but is random.
The master Vol. and reverb knobs are the only ones affecting it.
I pulled the 3rd pre-tube from the end as it was running much hotter than the rest, and found it to be GTECC83?? It seems to be the prime offender.
How ever the reverb and both channels still work without this tube.
What is the function of this tube?? Trem...??
I am thinking i will replace all the preamp tubes.
Please Chime in.
Kenny
_________________
MSA 12 String E9th/B6th Universal.
Little Walter PF-89.
Bunch of stomp boxes |
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Rick Johnson
From:
Wheelwright, Ky USA
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Posted 24 Jan 2008 11:50 am
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Ken
Here is the tube layout facing the rear of the amp
4 6L6GC Power Tubes
12AX7A 1st stage gain
12AX7A 2nd stage gain
12AT7 Rev Driver
12AX7A Rev Return
12AX7 Tremolo
12AT7 Phase Inv.
I wouldn't substitue a 12AT7 with a 12AX7A
Rick
www.rickjohnsoncabs.com |
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Ken Metcalf
From:
San Antonio Texas USA
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Posted 24 Jan 2008 1:46 pm
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Thanks Rick,
I want to get optimum (Clean) Steel tone.
Having been told before that if I swap this tube for that I can get a diff. sound, being confusing and not remembering it all.
The Vibrosonic sticker says.
6L6, 6L6
6L6, 6L6
12AT7
12AX7A
7025
12AT7
7025
7025
I know some of these cross over,
Are the tubes in your post above this reflecting a cleaner sound..? Stock set-up, hybrid Steel??
Thanks Kenny
_________________
MSA 12 String E9th/B6th Universal.
Little Walter PF-89.
Bunch of stomp boxes |
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Marvin Born
From:
Ohio, USA
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Posted 24 Jan 2008 2:25 pm Vibrosonic.
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I suggest you try another test.
Put all the tubes back where they were.
Note, an ECC83 is the same as a 12AX7 or 7025
Determine that the amp is working normally, (except for the noise) Set the volume controls, including the master to normal playing position. turn the reverb up until you hear the noise. Make sure you can hear actual reverb on the audio.
Locate the plugs for the reverb, there are two lines, both RCA jacks, either on the back of the chassis or on the chassis. Turn down the reverb all the way and unplug both of the wires. (keep track of where they go. ) Turn the reverb back up.
IF the noise is still there, there is a problem with the reverb return amp circuit. Swap the ECC83 with one of the input preamp tubes, (not a 12AT7) It will be another ECC83, a 7025 or 12AX7. See Rick's post for the location of the Rev Return, and a first stage preamp tube. Note if the ECC is bad and you move it to another stage, there may be a new louder noise from the amp. This is good in that you moved the noise and you will want to replace the ECC83. put the preamp tube back in its normal socket.
If the nosie went away when you unpluged the reverb, then the problem is either in the reverb tank or the 12AT7 stage before the reverb.
Do the test as suggested and post the results.
On the side of the amp cabinet, there is a white paper, please post the number on the sticker, it will be something like AB-270 or maybe 5E8, that will help determine exactly what circuit is in your amp.
Marvin |
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Ken Metcalf
From:
San Antonio Texas USA
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Posted 24 Jan 2008 7:29 pm
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Thanks Marvin,
I unplugged the reverb and it still made a hum, and some popping etc. I Swapped the rev return tube and 1st pre.
It got some what better and then made a big bang, pop, similar noise with out the reverb of course.
Then I switched the rev driver tube with the phase invert tube and it seemed to improve. But it still had a hum when the reverb knob was turned up.
This is good as I have found bad tubes.
Not too sure about the hum..
As far as the circuit type, I found the tube sticker on the side, inside the cabinet, but no numbers as you described.
Please chime in as I am going to order a new set of preamp tubes and am some what mixed up from the above tube recommendations and the paper inside the amp. Verses swapping different tubes for diff. results??
Thanks a bunch
Kenny  
_________________
MSA 12 String E9th/B6th Universal.
Little Walter PF-89.
Bunch of stomp boxes |
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Marvin Born
From:
Ohio, USA
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Posted 24 Jan 2008 9:07 pm Vibrosonic
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I suspect you have a bad ECC83 or 12AX7. The phase inverter is ususally a 12AT7 and if that is the case you would get an invalid test swaping it around with a 12AX7. The 12AX7 has more gain than the 12AU7.
I would dis-regard the hum for now. The open connections with the reverb unpluged could cause hum.
Confirm, that you have two input channels, for example two volume controls plus the master. Such as Normal and Vibrato, if so you have two input preamp tubes and can borrow one. The should be 12AX7 or eqiv.
Put all the tubes back to normal. Then remove the 12AX7 from the input channel you do not use (probably "normal) and swap it in place of the ECC83 for the reverb amp (or the suspect tube.)
Leave the tube out of the socket that you borrowed the 12AX7 from, that channel will be dead, just turn the volume to zero plug in the reverb, power up and set the reverb to normal playing setting and see what happens. If the noise is gone, then you have a bad tube.
Rather than replace the whole set of tubes now, just buy a single, 12AX7 or 7025 or ECC83 from the local Sam Ash, etc. Or borrow one fomr someone local, and put in in place of the reverb tube with all the tube in there normal location. IF the new reverb tube does not solve the problem it maybe time to find a good amp tech. |
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Ken Metcalf
From:
San Antonio Texas USA
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Posted 26 Jan 2008 11:08 am
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Thanks Marvin
I bought a new 12AX7 and put it in and after putting the tubes back the way they should be  
The amp was noticeably louder and better.
Thanks Again
Kenny
_________________
MSA 12 String E9th/B6th Universal.
Little Walter PF-89.
Bunch of stomp boxes |
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Marvin Born
From:
Ohio, USA
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Posted 26 Jan 2008 1:53 pm 12AX7
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I am glad the amp is working better.
Keep in mind that the orginal tubes, expecially 12AX7 are very valuable, and sound better than present day new tubes. Always keep your vintage tubes in the preamp section. The new 12AX7 in the reverb will have little effect on sound. And if you decide to replace all the pre-amp tubes, keep the old ones, you may want to use one in the first stage later.
Marvin |
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