SWR SM-400 Bass Head Biasing?

[kdawg]

I just received a schematic from SWR for an SM-400R bass head, but they informed me that they can't send me the voltage biasing procedure because of "legal issues". Does anyone know what this procedure is? I talked to an SWR service shop in Los Angeles and they said they can do it, it involves a scope and signal generator.

There is a bias adjustment for the tube preamp section, and one for the solid state amp.

I can email the schematic if someone is willing to help me out.. thanks!

-kdawg

 

[Test Point]

kdawg...pm me your email address and I'll send it to you..it's a small pdf
TP

 

[clintrubber]

There is a bias adjustment for the tube preamp section,

:?: That'll be for the FET-limiter then ?

I haven't heard of the SM-400R-version, but if anyone needs the old handdrawn SM-400 schematics just tell.

 

[kdawg]

Oops... SM-400S. Anyhow, I got the biasing procedure - thanks. They are basically offset voltages to keep the amp running more efficient as far as I know.

 

[clintrubber]

400S, all fine - IIRIC that version is having a bit higher output power.
And already has that transparancy-EQ-knob etc.
Nice amps, just be sure to support them @ the rear since I've found out that that nice Alu enclosure can break :evil: :evil: (Alu enclosure & a rear-mounted power-TX, aaaargh)

Bye,

Peter

 

[toddgw]

kdawg...pm me your email address and I'll send it to you..it's a small pdf
TP

Could I please trouble you for a copy of the SWR sm-400 BIAS procedure? Thank you for time.

 

[S.Samuelsson]

Hi.

Since Google isn't actually a search engine anymore , searching for something meaningful is sometimes awfully hard.

But, from an old discussion at TalkBass:

https://www.talkbass.com/threads/swr-sm400-problems.931153/
the original SWR bias procedure can be found in post #6

http://mhumhirecords.org/DIYpages/schematics/SWR/Bias.pdf
There's wealth of all kinds of SWR related information about all the Steve's creations at TB, might be worth a look if You haven't already.

Regards,
Sam