Need advice on Twin that took a dive.

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Gaz
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Need advice on Twin that took a dive.

Post by Gaz »

My friend brought me his Silverface Twin Reverb that took a fall off a 6x12, yes, a 6x12.

It looks relatively good, but had a broken tube, only because the chassis bent inward around the PT, causing the tube to smash into it since the tubes are already so close. I will need to try and bend the chassis back to fit in some new 6L6s, and would appreciate any advice on the best way to do that.

My other concern is the black sh#t coming out of the PT. I'm really hoping someone will tell me it's normal :) I have a feeling it might be since the mains fuse didn't even blow (the amp was still on after it fell!) It smells kinda burnt, but there is a blown screen grid resistor nearby, and I can't tell if it's just that.

Nothing else looks physically broken, however I haven't checked the tank yet.

Thanks for any help!
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Reeltarded
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Re: Need advice on Twin that took a dive.

Post by Reeltarded »

Use a soft pine 2x4 as a dolly and a mallet on a 1x1 piece of harder wood to whack it with.

I know what that stuff is. It's disgusting! Is it melty sap and corrosion mixed together?
Signatures have a 255 character limit that I could abuse, but I am not Cecil B. DeMille.
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Leo_Gnardo
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Re: Need advice on Twin that took a dive.

Post by Leo_Gnardo »

Gaz wrote: My other concern is the black sh#t coming out of the PT. I'm really hoping someone will tell me it's normal :) I have a feeling it might be since the mains fuse didn't even blow (the amp was still on after it fell!) It smells kinda burnt, but there is a blown screen grid resistor nearby, and I can't tell if it's just that.
PT's that have been in use for a long time sometimes have been through some abuse. Even ones that havent, often have some dark brown or blackish goop. Could have been there all along. Really bad cases of overheated PT's can coat the inside of the chassis with a layer of yellow-brown residue and that's a bad sign for sure. I don't see that in yours.

You won't know for sure until you fire up & let the amp run for a while. Of course you'll be setting bias correctly & that will do a lot to keep things running 'inside the dotted line.' Would be a good idea to exercise all caution on starting 'er back up, light bulb current limiter & variac. If all seems well, it is. If not, you'll be PT shopping, rats. Let's hope we don't have to go there.
down technical blind alleys . . .
Prairie Dawg
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Re: Need advice on Twin that took a dive.

Post by Prairie Dawg »

If the stuff is sticky, then it's the wax that the transformer was potted with. If it is not sticky, it's lacquer that was used for potting, nothing to worry about.
In either case run it until it burns out. That may be tomorrow, it may be never. I've found a number of transformers that had leaked some wax over the years but ran just fine.
If you believe in coincidence you're not looking close enough-Joe leaphorn
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Structo
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Re: Need advice on Twin that took a dive.

Post by Structo »

Yes they used to pot the transformers with crap that looks like tar.

When the PT gets hot it can melt it and result in what you have there.

Once you repair the amp, be sure to check the bias and run the amp for an hour or so.
If you can't touch the PT because it is too hot, then you may have issues at a long gig.
Tom

Don't let that smoke out!
Gaz
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Re: Need advice on Twin that took a dive.

Post by Gaz »

Thanks for all the replies!

I managed to flatten out the chassis today with some 2x4 scraps and my father inlaw's vice. It's pretty good besides one small area of the corner I couldn't get to.

The transformer is okay too! I fired it up with some spare old tubes and everything is working order including the reverb tank, which I was concerned about.

Now all I need is new power tubes and some new speakers since the magnet fell off one of them.

want to put some Jensens in there, but don't know if the C12Ns can handle the amp at 50W each. What do y'all think? should I go up to the C12Ks (100W each)?
matt h
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Re: Need advice on Twin that took a dive.

Post by matt h »

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Firestorm
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Re: Need advice on Twin that took a dive.

Post by Firestorm »

That amp can barely do 80W dimed, so anything claiming to be a C12N equivalent is just fine. I actually like the Italian C12Ns. The Ks are awfully clean for an amp that's already clean. Weber are nice; Eminence; Jupiter.
Firestorm
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Re: Need advice on Twin that took a dive.

Post by Firestorm »

Oh. I meant to throw this out to anybody who has tubes crash into to PT: 3M makes this plastic fiber steel wool substitute; a little spongy, pretty high temperature - I glue a little strip of it along the PT edge in case. Sometimes I put KT88s in these. Talk about a tight fit!
Gaz
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Re: Need advice on Twin that took a dive.

Post by Gaz »

Awesome, thanks. Yeah, I'm just going with the Jensens since it's not my amp. They are cheap, sound Fender-y, and don't look insane in case he wants to sell it (like the oooo-gly (but nice) Patriots).
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renshen1957
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Re: Need advice on Twin that took a dive.

Post by renshen1957 »

Gaz wrote:My friend brought me his Silverface Twin Reverb that took a fall off a 6x12, yes, a 6x12.

It looks relatively good, but had a broken tube, only because the chassis bent inward around the PT, causing the tube to smash into it since the tubes are already so close. I will need to try and bend the chassis back to fit in some new 6L6s, and would appreciate any advice on the best way to do that.

My other concern is the black sh#t coming out of the PT. I'm really hoping someone will tell me it's normal :) I have a feeling it might be since the mains fuse didn't even blow (the amp was still on after it fell!) It smells kinda burnt, but there is a blown screen grid resistor nearby, and I can't tell if it's just that.

Nothing else looks physically broken, however I haven't checked the tank yet.

Thanks for any help!
PS Peter Traynor used to test amps by throwing them out of the upstairs window of Long and McQuade
Every Tom, Dick, and Harry is named Steve
Zippy
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Re: Need advice on Twin that took a dive.

Post by Zippy »

renshen1957 wrote:PS Peter Traynor used to test amps by throwing them out of the upstairs window of Long and McQuade
Traynors were a lot more rugged than silverface Fenders. I played through a Traynor YGL-III Custom in the '70s. Traynor was using serious ply where Fender was using chipboard.
gldtp99
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Re: Need advice on Twin that took a dive.

Post by gldtp99 »

I put WGS G12C/S 75 watt speakers into a '74 Twin Reverb that I rebuilt last year.:


Vid:http://youtu.be/MptUOmsSPDY

WGS G12C/S speakers: http://wgs4.com/12-g12cs-75-watts
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