Restoring an old Garnet amp

[mayfly]

Thanks man!  :icon_thumright: <sniff>

 

[Nando Vallart]

Never heard of Garnet amps before! Cool work, as always, Mayfly!

 

[Cagey]

Holy mackerel! I thought you were just gonna reverse what you'd done, but this is essentially a scratch build. Other than the vintage-correct wire on the output jacks, of course. Good thing you left that, or you'd never be able to sell it.

 

[mayfly]

so while waiting for the book I plugged the tweeter hole

just cut a plug with a hole saw.  Plug was a bit small so I filled the gaps with a chunk of wood that I cut notches in (like acoustic guitar linings) to make it curve.  smaller gaps were filled with a slurry of sawdust and titebond III and the hole mess is soaked in titebond III.  That should hold it!

 

[mayfly]

Also - found this photo on line of a "revolution II".  I don't have this schematic, but it looks very very close to what I remember my original wiring looking like:

the stuff on the upper left is the footswitch and pot for the lead boost.  the little transformer is the  reverb driver, which I still have.  So I think I have a "revolution II" - and I know it's out there!

I just need to find that schematic....

 

[Tonar8352]

I love it; that is what an amp is supposed to look like on the inside, lots of goodies and no printed circuit board. I can't wait to hear it!

 

[mayfly]

Gentlemen,

I have received the garnet book.  A couple of observations:

1 - even at first glance, the book is excellent.  It's pretty cheap too - cheaper than the London Power series of books by a long shot.  I strongly recommend this book - and I've read them all.  Max:  buy this book.

2 - the schematic is in the book!  Turns out I have a G100TR "revolutionIII".  Everything seems to match up with that circuit.

Now it's time to get the parts list together, see what I have, and then order the rest. 

Let's get 'er done!

 

[mayfly]

For those who may not know,  Garnet amps were made to create some very famous sounds.  The lead tone on every The Guess Who song for example, and Grady's country death metal tones as well.

Here's a little video with some clips and history on these great amps!

www.youtube.com/watch?v=koykStZtUhM

Update - it also has Peter Traynor in there!  That's kinda cool...

 

[mayfly]

Nothing like learning a schematic like drawing it out:

Between mouser, AES, and my junk box all the parts are on order.

Next:  I'll draw out an appropriate wiring diagram.

 

[mayfly]

ok check out the garnet back line of the great great sadies!

www.youtube.com/watch?v=HtG0w9lGfnc&feature=related

 

[Mor Paul]

So, that's where you get your taste in shirts from!

 

[fdesalvo]

I love graph paper.  Nice work! 

 

[mayfly]

Not much to report.  Waiting on parts.

In the mean time, I'm reforming a NOS Mallory can cap that I had in the parts drawer:

I'm using my home made tube amp bench supply for this.  It's a +400VDC, -50VDC, +6VDC, 6VAC supply.  Perfect for all your tube experiments!  :icon_thumright:

 

[mayfly]

More updates.  I've build the B+ supply, bias supply, and hooked up the heaters.

Then I made the mistake of starting on the output section.  I didn't think it through and ended up wiring up the phase splitter on the tube next to the power supply (the socket at the top of the photo).  Turns out on garnet amps the phase splitter is the one in the MIDDLE of the chassis - the one close to the power supply is reserved for non signal path things like the trem oscillator.  oops.

Looks like I'll be taking out that nice pair of mallory 0.047 uf caps.  sigh.

 

[fdesalvo]

How dare you follow a logical layout.

...Then I made the mistake of starting on the output section.  I didn't think it through and ended up wiring up the phase splitter on the tube next to the power supply (the socket at the top of the photo).  Turns out on garnet amps the phase splitter is the one in the MIDDLE of the chassis - the one close to the power supply is reserved for non signal path things like the trem oscillator.  oops.

 

[mayfly]

Gentlemen,

I've progressed further.  The preamp and half the reverb circuits are wired.  Sadly, I'm off to a trade show for a couple of weeks, so more will have to wait.  Here are some photos of the progress:

I'm doing this all flying lead style.  I have to confess I'm working fast and not being that careful, but it's true to form to how the amp was originally made!

 

[Cagey]

Won't be long now, eh?

A couple weeks for a trade show? Seems awfully long.

 

[mayfly]

ok folks,

I just got it wired.  Here's some shots:

Now it's time to bring it up.  First the power supply, then the power amp, then preamps and effects. 

Here we go...

 

[mayfly]

Power supply works.  All B+ notes are ok, as well as the bias supply.  Now to put some tubes in it and see if it will generate power. 

oh - and if you're inclined to do stuff like this, get one of these:

50 ohms, 20 watts, on alligator clips.  In case it's not obvious, this is for draining the filter caps.

 

[mayfly]

Input is on top, injected into the grid of the phase splitter.  Output is on the bottom, run into a dummy load.  Hmmm - nothing yet there...