A Peek Inside The 1967 Fender Twin Reverb

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Last year, I acquired this abused and forlorn “blackface” Fender Twin Reverb amplifier.  We see a lot of vintage pieces here in central Florida with many of the same issues that this one had when it came in.  It had clearly been improperly stored and had seen heat and humidity over many years or had gotten wet from rain or flood.  Once we determined that we had good transformers on board, the work could begin in earnest.

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This first “before” picture shows the original bias supply pot and some original wire.  You can see how compromised the wire is.  It has been wet and dried out more than a few times.  Also, it was necessary to lift the pot and clean the chassis underneath to ensure a good ground to the pot.

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This next pic shows the non-original resistors on one of the old power tube sockets.  They will definitely go away, but in the process I decided to just replace the old sockets as well.  The primary goals here are good tone and reliability.  I always like to leave original parts where I can, but not at the expense of sound and dependability.

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This problem shot shows still more moisture damage and several suspicious looking rectifier diodes.  Everything here will be replaced in the interest of quiet operation and  the board cleaned up.

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A whole bunch of these original resistors have started to crumble over time.  They make a real racket when tapped with a chopstick under load.  Most of this wire has become brittle and noisy with age and hard use.  I didn’t know it when I took this photo, but I would soon elect to remove it all.

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In this last “before” photo we can see the input, tone stacks and plate resistors for both channels.  Someone has already replaced the original 100k carbon comps with carbon films.  This is generally a good choice if they have become noisy.  I don’t know if the noise was at an acceptable level because that decision was already made, so we will just go with it.

What follows now is a short video clip to show the completed internals of the amplifier.

 

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