Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: TubeJunkie on January 12, 2020, 11:21:41 am

Title: Excelsior Americana 50WR (Sano) Scratch Build - Schematics
Post by: TubeJunkie on January 12, 2020, 11:21:41 am

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

Here are the original schematics:

Pre-amp
(http://2.bp.blogspot.com/-PvHVV3SDaTU/UWjhYsYe__I/AAAAAAAACS4/IXqCi65NHVQ/s1600/Excelsior+preamp.JPG)

Power Amp
(http://1.bp.blogspot.com/-Ap00oYhq574/UWjhY-jjEGI/AAAAAAAACTA/bNS_3lIZ5S4/s1600/ExcelsiorSchematic.JPG)

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.

Title: Re: Excelsior Americana 50WR (Sano) Scratch Build - Schematics
Post by: sluckey on January 12, 2020, 01:41:23 pm

couple things stand out...

1. All the power supply caps are ackwards.

2. The reverb input is connected to the ground side of the main OT. Should be connected to the hot side.

Title: Re: Excelsior Americana 50WR (Sano) Scratch Build - Schematics
Post by: TubeJunkie on January 12, 2020, 02:27:23 pm

Quote from: sluckey on January 12, 2020, 01:41:23 pm

1. All the power supply caps are ackwards.

2. The reverb input is connected to the ground side of the main OT. Should be connected to the hot side.

Woops . . . fixed (below).

Thanks sluckey.  Any idea about the unreadable resistor?

Title: Re: Excelsior Americana 50WR (Sano) Scratch Build - Schematics
Post by: sluckey on January 12, 2020, 03:04:21 pm

I think it's 680K

Title: Re: Excelsior Americana 50WR (Sano) Scratch Build - Schematics
Post by: TubeJunkie on January 12, 2020, 08:59:56 pm

Made some changes . . .

After some helpful input, I've removed R38 1M and C20 .022uf from the end of the pre-amp section since it appears they were there only to keep DC from leaking into the signal path as a result from the splitting of the chassis and using a shielded jacket for the wire runs between the chassis.  Also includes the errors found by sluckey.