Excelsior Americana 50WR (Sano) Scratch Build - Schematics

TubeJunkie

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I'm doing a scratch build of an Excelsior Americana 50WR amp (built by Sano), but the schematics left a lot to be desired. I've re-drawn them, and would appreciate feed-back on the result. I've cleaned them up, and hopefully eliminated some confusion of what goes to where (with help from a few members on the forum here). This article at Vintage Guitar piqued my interest:

https://www.vintageguitar.com/17184/excelsior-americana/

Here are the original schematics:

Pre-amp


Power Amp


I believe I've interpreted/deciphered everything correctly, except for the resistor value shown below. My best-guess was 680k . . .

Also below are my re-drawn schematics. The first one is of each separate section, and the second one is just one big schematic.

Thanks in advance for any and all help/feedback.

Resistor Value.jpg


My best-guess was 680k . . .
 

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Soul Tramp

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I'd ditch C19 and R38, and change R40 to 1M. R22 is an oscillation filter and still needs to be assigned a value.

I'm too lazy to look it all over. Best of luck with the build. Will be fun to watch.
 

TubeJunkie

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I'd ditch C19 and R38, and change R40 to 1M. R22 is an oscillation filter and still needs to be assigned a value.

I'm too lazy to look it all over. Best of luck with the build. Will be fun to watch.
Soul Tramp, thanks for the input. I get the change of R40 to a 1M, butv what's you're reasoning for dumping C19 and R38 (I believe they had something to do with the original connection to the polarity and standby switching); and what do you mean by assigning R22 a value? The re-draw has R22 as a 500k A Treble pot for the lead/tremolo pre-amp section. Do I have another R22 somewhere?

I've seen your web site and looked at your amps. I like the twist you put on your amps. This is one of several amps I have in the works, and I'm just starting preliminary work on this one. I've become intrigued with non-typical amps and have these amps in line: Supro Thunderbolt with a cascaded lead channel taking advantage of the unused portion of the V1 12ax7; a Hotrod Blues build that's a mash-up of a Princeton and Blues Jr.; and a National/Valco 1215 Professional that uses 6SN7, 6SL7, and 6SJ7 tubes.
 

Soul Tramp

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In the -3 .pdf, R22 does not have a value assigned.

I'm guessing the signal path between C19 and C20 is a connection between two different chassis. C20 is likely a trap for an DC that may leak into the signal path.
 

TubeJunkie

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I'm sorry, I've been looking at these schematics for too long. I've looked and looked, and for the life of me I can't see an R22 resistor without a value.

You're correct about there being two chassis. The original amp had two chassis: one at the top of the cabinet for the reverb amp; and one at the bottom for the main amp. A shielded jacket was used for the back-and-forth cable runs, and the original schematic showed the grounding of the jacket, as seen in the image below. The crosshatched area with the ground is the jacket being grounded, which is just before C20 and R38. That would make sense eliminating either C19 or C20 as well as R38.

Shielded Jacket.jpg
 

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Soul Tramp

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The resistor (R22) is at the start of the signal path.

R22.jpg
 




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