Overdrive Deluxe amp

[dorrisant]

If someone wants to post the preamp board dimensions from a blackface or silverface, I will rearrange the preamp parts to fit and produce a second set of files that correspond.

[didit]

Hello --

If someone wants to post the preamp board dimensions from a blackface or silverface [ ... ]

From my 1964 AB763:

Overall board dimensions are 14 5/8" x 2 1/2". There are just three bolt through-holes for mounting. These are slightly misaligned across the longer edge. Starting from the power transformer end the first hole is just 5/8" from the end and centered on 1 1/4" per side; next is offset 6 5/8" toward middle and just 1 1/8" from the front; the third is another 5 5/8" further, so 1 3/4" from the far edge, and is set only 1" from the front.

For reference, a fairly clear close-up picture of the board with a steel rule guide, set roughly flat given all the various components and wire above the surface.

1964 Deluxe Reverb board closeup.jpg

Best ..

PS -- Please do not misconstrue this as endorsement to rip apart any early mid-60s DRs in hopes of reproducing Dumble's interesting designs. Leave 'em alone and source from the abundance of readily available components, including chassis, transformers, etc ...

[Guy77]

Wow only 3 screws to hold such a large board. It works so don't change it I guess.

Thanks for posting!

Cheers
G

[martin manning]

Three screws and a bazillion pretty stout wires...

[didit]

There is also the insulating "backing" fibre board that in sum makes for a fairly stiff sandwich ..

[dorrisant]

Hello --

If someone wants to post the preamp board dimensions from a blackface or silverface [ ... ]

From my 1964 AB763:

Overall board dimensions are 14 5/8" x 2 1/2". There are just three bolt through-holes for mounting. These are slightly misaligned across the longer edge. Starting from the power transformer end the first hole is just 5/8" from the end and centered on 1 1/4" per side; next is offset 6 5/8" toward middle and just 1 1/8" from the front; the third is another 5 5/8" further, so 1 3/4" from the far edge, and is set only 1" from the front.

For reference, a fairly clear close-up picture of the board with a steel rule guide, set roughly flat given all the various components and wire above the surface.

1964 Deluxe Reverb board closeup.jpg

Best ..

PS -- Please do not misconstrue this as endorsement to rip apart any early mid-60s DRs in hopes of reproducing Dumble's interesting designs. Leave 'em alone and source from the abundance of readily available components, including chassis, transformers, etc ...

This looks perfect! Thanks for that. And no, I never intended to desecrate anything. If the board was bad for any reason it would need to be replaced. This happens enough that this may be an option at that point. Also, if you find a SF in desperate need of repair, this may be that best option. If you use epoxy/fr4/Garolite board, you only need three standoffs for solid triangulation... and no backer board is needed if you stand it off by 1/4" or more.

[aab0mb]

I was looking at some pics of the original reverb advertisement for when this amp was for sale and noticed what I thought to be a lack of rectifier tube. Upon finding some Sebago amps for sale, someone had pulled the tubes out for display and there was no rectifier tube shown.

So we know it’s solid state rectified and perhaps we can further assume this means beefed up filter caps as we see in some Dumble designs and mods. Not sure if we mentioned the rectification detail in any of the previous discussion.

Anyone having luck with this build?

[Smokebreak3]

Funny you should ask, I was just about to pull mine into rotation and do some playing. Mine sounds killer, though it is tube rectified
I think we still had a few other unanswered questions didn't we? A pot value and probably voltage divider or something between stages iirc

[aab0mb]

Funny you should ask, I was just about to pull mine into rotation and do some playing. Mine sounds killer, though it is tube rectified
I think we still had a few other unanswered questions didn't we? A pot value and probably voltage divider or something between stages iirc

Both inputs confirmed 1 Meg impedance. I got someone to plug in a cable and measure across tip/ground. 100k or 250k (audio or linear taper in question) first stage drive pot seems workable. Prob too much gain otherwise.

[Smokebreak3]

Something I just realized today, the treble pot acts very oddly in this amp because of the loading of the trem pot. You get the same sort of signal dump as you do in a typical bf/sf fender circuit, but because it is right at the treble pot, it acts more like a "thin knob", as you turn it up. The amp actually gets thicker and louder as you turn the treble down, and vice versa the other way.
All to say, It made me start to think that maybe the trem pot isn't the standard 50K

[Rollylama]

Something I just realized today, the treble pot acts very oddly in this amp because of the loading of the trem pot. You get the same sort of signal dump as you do in a typical bf/sf fender circuit, but because it is right at the treble pot, it acts more like a "thin knob", as you turn it up. The amp actually gets thicker and louder as you turn the treble down, and vice versa the other way.
All to say, It made me start to think that maybe the trem pot isn't the standard 50K

I recently got the Sebago and have noticed something else about the treble pot. I’m getting some buzzing/distortion on the “clean” input 2…different guitars/cabs/speakers with same result but not on the OD input 1.

I tried chasing it physically but I believe it might be in the circuit itself because it stops when I roll the treble down all the way. It’s as if the signal is getting overloaded.

No idea what could cause this…hoping it’s a tube but I can’t check until this evening.