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.

 

[Mudhiker]

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

Not yet.  They are sitting here on my desk in the pile.  Will update when I do get to them...

 

[Grainger49]

Mudhiker, You and I are the kings of procrastination.  Don't feel bad, we have company.  They just don't admit it.

 

[dmannnnn]

Mudhiker, You and I are the kings of procrastination.  Don't feel bad, we have company.  They just don't admit it.

I resemble that remark.

Seriously, I will get to them sometime.  I just finished a refurb on the old Marantz HD770's.  So that leaves a magnepan crossover upgrade, Miracord 50HII plinth build, Step-up transformer build..... I will have them done by late 2011, promise.

 

[dmannnnn]

...I completely forgot about the pair of Knight 615HC triaxial (rebadged Electrovoice 15trx) speakers I put in storage.  Any suggestions for a sanely sized encosure for these would be appreciated.

 

[pro_crip]

The original links for these gems no longer works. They are available here: http://stores.ebay.com/Combat-Super-Store. I bought a pair of the 2 disc versions (he's got 1 disc versions as well) as a future stepped attenuator for my FPiii. I imagine those won't fit in the chassis so they'll probably get their own box. I plan on putting in Goldpoints or some such thing when I build. As an aside, that store has a buttload of caps available. There was also a 330 ohm 1kw wirewound resistor in there, talk about huge.

Rich