What circuit is my Twin Reverb?

[Axtman]

I am unmodding and restoring a Fender Twin Reverb Silverface. The amp has a master volume but does not have the pull boost feature. Inside chassis there is the printed date of 1972. The amp uses a 2 prong plug. The chassis is stamped A41164.

What circuit is this amp?

Thanks!

[RWood]

It looks like it is an early version of this one that still uses a two prong plug.

The earlier schematic from 5/68 does not have a master volume.

Is anything stamped on the tube chart?


RWood

[tboy]

Just curious; what sort of mods have been done to it?

[Gibsonman63]

The two pronged plug seems a bit strange to me. I have a 1972 Super Reverb (transformer date codes) with the red three-pronged plug and no master volume. Of course I had to change the end out because the previoius owner broke off the ground.

[Axtman]

The amp came with a poorly home made amp cabinet, so there is no tube chart.

As far as mods go. The first channel does not work and there is no tremolo.

I want to bring this thing back to its formerly glory.

[Bruce / Mission Amps]

OK.. you want help but are not giving up too much so take a digital picture of the inside of the chassis so we can see what's in it...

[Axtman]

Here you go!

http://i899.photobucket.com/albums/a...cture001-1.jpg

http://i899.photobucket.com/albums/a...cture002-1.jpg

http://i899.photobucket.com/albums/a...cture003-1.jpg

http://i899.photobucket.com/albums/a...cture004-1.jpg

[bob p]

that chassis looks like its lived a hard life.

[überfuzz]

It seems to have a master volume knob. Does it have a push/pull function?

(If I remember correctly: master volume 1972, master volume with push/pull 1973 and later.)

[Axtman]

As I said in my first post, it has a master volume but no push pull boost.

[Alex R]

It has a chassis ground (green wire), so that two pin plug can go. And is probably not standard.

[Euthymia]

It looks like it at least has had the PI resistor values blackfaced.

I suggest you leave that alone, if it has been done. The blackface resistor values from the PI downstream really make a Twin sound great.

If I were working on this amp, I'd just refer to the AB763 schematic.

[Axtman]

I installed a new 3 prong plug because the old cord was in frayed. I accidentally broke the fuse holder and bought a new one today. The "cockroach" optical resistor is missing so it does not have vibrato.