Interesting ebay find

[dmannnnn]

They arrived today.  A pair of surplus 35 position rotary switches, shorting style, unused.  These look like they came off a control panel from a Siberian Nuclear power plant.  Not the smoothest mechanism, but not too bad either.  They are 3.5" a side and 3" deep.  I will report back on them once I can get them loaded with resistors.  It might be awhile though.  If they can hold the contact well while switching they should work out pretty good.

Price on these is $34/pair shipped.  I was thinking of a passive preamp in a bottlehead size chassis.



Close up of contact mechanism



http://cgi.ebay.com/Powerful-rotary-sliding-switch-35-steps-2-discs-2-PCS_W0QQitemZ250453363226QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item3a502f0a1a

[Grainger49]

Booger!  Those are industrial all right.  They look like the stuff in the first mill I worked in.  All the machinery had been built in 1942, built to last a hundred years.  Serious stuf there!  The controls were mounted on 2" thick slate panels.

Do you mean make before break when you said shorting?  I'm interested in a pair.

[ssssly]

Now those are some beefy rotary switches. You could use non inductive wirewounds to populate that thing.

[dmannnnn]

Yes they are make before break.  You can see the wiper spanning both contacts while switching.  I tried to test them with the DMM and it seems to be okay.  I won't know if they switch without noise until I get a signal going through them.

[Grainger49]

I don't care if I don't need them.  They look so cool I'll have to order a pair.

[Mudhiker]

Just pulled the trigger.  Now I gotta figure out how to calculate all the resistors to populate them with.  Most of the online calculators I've seen are for 24 step attenuators.

[dmannnnn]

Post a link if you find a good calculator.

[ssssly]

I wonder what these were initially used for? We will probably all end up on some sort of watchlist for buying Russian reactor parts or the like.

[Grainger49]

VoltSedond's Attenuator page has a calculator for resistor values.  It has a tab on the excel spreadsheet for different kinds of attenuators.  The advantage of the S5 is it only has 2 resistors in the audio path at a time.  It takes the number of steps and one more resistor.

http://www.siteswithstyle.com/VoltSecond/12_posistion_shunt/12_Position_Pure_Shunt.html

It is the Zip file in magenta about 1/2 way down the page.

[Mudhiker]

They just arrived today. These things are MASSIVE!  I was planning on putting them in a 2u chassis but it's gonna hafta be a 3u.

[Grainger49]

Mudhiker,  

I have been watching some just because I want to do this when I get my next temp job.  I had imagined they were large but I have no idea how large.

Can you post a picture showing one next to a quarter?  A Bottlehead product?

(changed my avatar since everybody in the thread has his dog)

[ssssly]

Has anyone populated one of these monsters yet? They look big enough to use tantalum resistors in them.

[dmannnnn]

I haven't touched them yet.  In the middle of a foreclosure. :-( Probably won't be til later this year unless I get a wild hair.

[dmannnnn]

VoltSedond's Attenuator page has a calculator for resistor values.  It has a tab on the excel spreadsheet for different kinds of attenuators.  The advantage of the S5 is it only has 2 resistors in the audio path at a time, but takes twice as many resistors..

http://www.siteswithstyle.com/VoltSecond/12_posistion_shunt/12_Position_Pure_Shunt.html

It is the Zip file in magenta about 1/2 way down the page.

Actually, the S5 configuration only adds one resistor to a standard stepped attenuator.  It uses a single resistor for each step with an additional fixed input resistor.  These can be made with a single pole (layer) switch.  The 'ladder style' configuration switches the input resistor and uses 2 resistors in each step.  This requires a 2 pole switch.

[Grainger49]

Yup, I wasn't thinking well.