DIY Stax self bias conversion?

[kevin gilmore]

you need AC 120v not 12v

and that is for low bias only

Edited December 29, 2020 by kevin gilmore

[Vlaca]

Yes yes, i edited my post.

Thank you!

Yes i need low bias for my sr5-nb.

[Vlaca]

Here is the edited, right schematic(low bias):
 

 

Thank you!

[ericj]

Necrobump! Was there ever an official published schematic for one of the SB transformer boxes? And if so can i have it? 

About the zener. There is some confusion to be sure. In the SRD-7 schematics, the part is listed as Z1100 and the symbol is very clearly a bidirectional zener, what would be commonly sold as a transient voltage suppressor today. 

There appear to have been parts called "Z1100" from a few companies and some of them were unidirectional. 

The component on the boards in my two SRD-7s has no stripe at all, just an "A" logo and Z1100. One end is slightly pointy but that is probably just sloppy epoxy work. 

Semitec made a Z1100 TVS diode until 2005. See attached datasheet. Littlefuse makes a P6KE100CA with similar specs. 

Given the nature of the SB energizers it may be that a unidirectional part works better in that circuit. Which is sort of why i would like to know if there was a published schematic. I don't have any SB energizers myself. 

 

SMTCD00017-27.pdf

[ericj]

OK, picked up a 7/SB on ebay for $50 + ship. Which was fair because this poor thing has had a hard life. There's rust, and wax melted out of the transformers. 

Yes, it's a unidirectional zener, marked 1Z100. My guess is that the current equivalent is ZY100 which will produce a voltage of about 83v at best, then 3x cockroft-walton and a 1uf reserve cap *before rather than after the ballast resistor, and the ballast resistor is 4.7M rather than the 2.2 or 3.3 specified in some of the wall-powered schematics. 

I'm pretty sure I've seen pictures of a 7/SB that had an additional transformer in the bias circuit but not this one, and the board looks identical to a gutshot of an SRD-6/SB i saw recently. 

I still think it's weird that i have yet to find a /SB official schematic. *shrug* maybe they never published one. Now i wonder what's in the fairly rare SRD-7/SBMK2. 

Edited April 18 by ericj
corrected part number

[ericj]