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Hey everyone, I just got my blackface Showman Amp and the tone is so
sweet! I have but one question and concern. When I engage the vibrato
it makes a pretty loud "fluttering or thumping" noise and the vibrato
isn't very "thick" Is it a bad tube? Or something internal? Other
than that she seems to work fine -Phillip
Hi,
The fluttering is quite normal with the Vibrato, given the fact it uses
some kind of photocel.
I recently talked about it with an amp tech and he said the fluttering
is quiete normal, but can be gotten rid of.
I seam to rember this was discused here a while ago, so you might want
to check the archives about this. Or ask at "fenderforum" at the
"FenderAmps before 85" group. (or search their archives about this)
My vibrato on my Fender BMR sings a bit when engaged. It's like a there
is a little bird trapped inside of it, quiete funny.(probably the
photocel) But it's only when I'm not playing, so not very anoying.
As for the tubes, there are two? Tubes involved driving the tremolo (I
think). A 12AX7 7 and half of a 8085? (or simelar).
So perhaps it could be one of those. And as with these amps, the problem
could be something else. I usually ask someone with expierience to have
a look at it. Most probably it's only something small.
Jerry S.
-----Original Message-----
From: Landlocked [mailto:]
Sent: vrijdag 23 januari 2004 5:41
To:
Subject: [SurfGuitar101] Fluttering Vibrato?
Hey everyone, I just got my blackface Showman Amp and the tone is so
sweet! I have but one question and concern. When I engage the vibrato
it makes a pretty loud "fluttering or thumping" noise and the vibrato
isn't very "thick" Is it a bad tube? Or something internal? Other
than that she seems to work fine -Phillip
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Hi Phillip,
A certain amount of fluttering or thumping is normal for the
blackface amps, I think...from what I have read on the Fender Forum.
My Showman thumped like crazy though, and I took it to the tech
twice. He replaced the photocell (bug) but to no avail. Finally I
replaced the tremolo driver tube with a NOS tube and WOW! The noise
simply vanished, and I suddenly had a very rich and thick tremolo.
Boy was I happy! It was quite a dramatic difference.
I'd have to go home and look at the back of the amp to tell you
which one it is. But the AB763 circuit used in the blackface
Showman, Twin Reverb, etc usually has a tube chart like this (I may
not have the order right):
4 6L6GC (power tubes)
2 7025 tubes (preamp for normal and vibrato channels)
1 12AX7 (tremolo driver)
1 12AT7 (rectifier?)
The 12AX7 is the tremolo driver that interacts with the photo cell.
Its just a noiser version of the 7025's. If you don't have another
12AX7 handy just swap it with one of your existing preamp tubes that
go in the 7025 slot (these are most likely 12AX7's anyway, since
7025's are not made anymore and are very scarce).
Apparently the NOS 12AX7 has a lower voltage gain than the brand new
JJ tube I had in there and doesn't drive it as hard. At least that
was the theoretical answer I got from smart guys on the Fender Forum.
I just know that "me replace tube with another one, it now sound
better, ugh," (caveman amp repair).
Good luck!
BN
--- In , "Landlocked"
<thee_surrealist@h...> wrote:
> Hey everyone, I just got my blackface Showman Amp and the tone is
so
> sweet! I have but one question and concern. When I engage the
vibrato
> it makes a pretty loud "fluttering or thumping" noise and the
vibrato
> isn't very "thick" Is it a bad tube? Or something internal? Other
> than that she seems to work fine -Phillip
Hey Brian thanks for the input. I've heard the "normal" flutter in my
late 70s Twin but this one is ridiculous!I've already tried
the "caveman" tube swap...unsuccessful. I thought maybe it was the
footswitch, but it wasn't. So I'm driving back up to Austin in about
a week to replace the "photocell lamp oscillator thingamabob..."--
Phillip
--- In , "Brian Neal" <bneal@i...> wrote:
> Hi Phillip,
>
> A certain amount of fluttering or thumping is normal for the
> blackface amps, I think...from what I have read on the Fender Forum.
>
> My Showman thumped like crazy though, and I took it to the tech
> twice. He replaced the photocell (bug) but to no avail. Finally I
> replaced the tremolo driver tube with a NOS tube and WOW! The noise
> simply vanished, and I suddenly had a very rich and thick tremolo.
> Boy was I happy! It was quite a dramatic difference.
>
> I'd have to go home and look at the back of the amp to tell you
> which one it is. But the AB763 circuit used in the blackface
> Showman, Twin Reverb, etc usually has a tube chart like this (I may
> not have the order right):
>
> 4 6L6GC (power tubes)
> 2 7025 tubes (preamp for normal and vibrato channels)
> 1 12AX7 (tremolo driver)
> 1 12AT7 (rectifier?)
>
> The 12AX7 is the tremolo driver that interacts with the photo cell.
> Its just a noiser version of the 7025's. If you don't have another
> 12AX7 handy just swap it with one of your existing preamp tubes
that
> go in the 7025 slot (these are most likely 12AX7's anyway, since
> 7025's are not made anymore and are very scarce).
>
> Apparently the NOS 12AX7 has a lower voltage gain than the brand
new
> JJ tube I had in there and doesn't drive it as hard. At least that
> was the theoretical answer I got from smart guys on the Fender
Forum.
>
> I just know that "me replace tube with another one, it now sound
> better, ugh," (caveman amp repair).
>
> Good luck!
> BN
>
>
>
Phillip - keep us posted. While I was doing research on the tremolo problem
for my amp, I found that there are lots of things that can go wrong with
this particular aspect. I was lucky that a tube swap was all I needed. The
bug can go bad, the cathode bypass capacitors in that circuit can go, etc.
There is a guy on the Fender Forum (handle: VintageJon) who sells what he
calls the "surf bug", its basically a heavy duty hand-built version of the
bug (the photo-isolator doo-hickey). If you search on the Fender Forum for
tremolo problems you will find lots of hits; people do all kinds of things
to try and quiet the blackface tremolo ticking. Good luck!
So how do you like the amp other than that? How old is it, and did you get a
cap job done?
BN
PS. Come to think of it, I think that VintageJon guy is from Austin Texas.
He's an amp repair guy, maybe he could help you out! Look for him in the Amp
Repair forum.
> -----Original Message-----
> From: Landlocked [mailto:]
> Sent: Monday, January 26, 2004 1:26 PM
> To:
> Subject: [SurfGuitar101] Re: Fluttering Vibrato?
>
>
> Hey Brian thanks for the input. I've heard the "normal" flutter in my
> late 70s Twin but this one is ridiculous!I've already tried
> the "caveman" tube swap...unsuccessful. I thought maybe it was the
> footswitch, but it wasn't. So I'm driving back up to Austin in about
> a week to replace the "photocell lamp oscillator thingamabob..."--
> Phillip
