Hammond Organ Amp to Guitar Amp Conversion Project

[Structo]

Another question I have is which pin on the 5U4GB rectifier is the B+?

The Hammond schematic shows it as pin 2.

Other schematics I have seen that use the 5U4GB, such as the Boogie Dual Rectifier have the B+ coming off of pin 8.

I have mine coming from pin 2.

My tube data program says pin 2 is F+.

Is that because it is a directly heated cathode, so it doesn't matter?

[skyboltone]

I think you mistyped. What the F is F+? And I think you are right. I've seen that before. The positive voltage is taken off at the cathode/filament; either end.

[Structo]

Heheheh, yeah that's the way the Duncan tube data sheet program labeled the pins.

Got any hints on my previous post about the oscillations?

[skyboltone]

Heheheh, yeah that's the way the Duncan tube data sheet program labeled the pins.

Got any hints on my previous post about the oscillations?

With no doubt in my pin pointed head; lead dress. Something is crossing something it shouldn't. That's the toughest part of makin up yer own stuff.

[Structo]

So here is what I did with this Hammond.

I shortened the chassis to 14 inches long.

I drew up a layout to scale and taped it to a Garolite 10 board.
Center punched where the eyelets went.
[IMG:800:600]http://i23.photobucket.com/albums/b392/ ... G_0006.jpg[/img]

Installed the 1/8" eyelets.
[IMG:800:600]http://i23.photobucket.com/albums/b392/ ... G_0007.jpg[/img]

Installed the components.
[IMG:800:600]http://i23.photobucket.com/albums/b392/ ... G_0011.jpg[/img]

Installed the new ceramic tube sockets.
[IMG:800:600]http://i23.photobucket.com/albums/b392/ ... G_0014.jpg[/img]

Installed the choke and output transformer.
Not the best layout but it's a bit cramped.
[IMG:800:600]http://i23.photobucket.com/albums/b392/ ... G_0020.jpg[/img]

And here is how it looks at this point.
I added the negative feedback and presence control.
The switch switches between a 5uf and 10uf bypass cap on V1b.
I may change this to either a larger cap or no cap for a non bypassed cathode.
[IMG:800:600]http://i23.photobucket.com/albums/b392/ ... G_0034.jpg[/img]
[IMG:800:600]http://i23.photobucket.com/albums/b392/ ... G_0022.jpg[/img]

I had a bad oscillation problem that I later traced to having the plate resistors backwards on the PI. They were drawn wrong on the schematic I had. So I switched the two resistors and also had to switch the plate wires.
Sounds pretty good, still a bit too gainy.

I'm having a bit of a problem with the range on the volume control.
There is very little range for clean before it gets loud and distorted.

[skyboltone]

So here is what I did with this Hammond.

I'm having a bit of a problem with the range on the volume control.
There is very little range for clean before it gets loud and distorted.

So try this:

[Structo]

Yeah, I tried that. Took it all the way down to 10k eventually.

Really didn't notice any difference between 470K, 220K, 100K or 10K.

What's weird, is that I will spend hours researching this stuff, doing the math, looking at different examples, etc.

Then I plug in the components that should work and they sound like ass.

I still like it best with the 832 in V1.
With a ax7 in V1 it's way to gainy. I've tried different ax7's and different plate and cathode resistor combos, I just don't get what is making this thing so hard to tame.

[stretch2011]

I just a AO-14-1e for $20 only one preamp tune In it tho.