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Ping: DAK

63.246.183.22
Posted on June 24, 2017 at 14:57:59
Triode_Kingdom
Audiophile

Posts: 10042
Location: Central Texas
Joined: September 24, 2006
 Apparently the nomenclature I used earlier regarding the rotary switch for your cathode current meter was incorrect. A shorting switch and a make-before-break switch are one and the same. I was sure a shorting switch is one that cumulatively shorts adjacent contacts together as the switch is turned, but that's not how manufacturers are presently describing them. In fact, during a quick search, I couldn't even find that configuration.

Anyway, I just wanted to point out a switch on eBay that would do what you need for the meter switching. I stumbled across it while looking for something else.

 

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RE: Ping: DAK, posted on June 24, 2017 at 17:43:19
Eli Duttman
Audiophile

Posts: 10455
Location: Monroe Township, NJ
Joined: March 31, 2000
 Many years ago, the resident engineer at Lafayette Radio's 100 6th Ave. NYC store, Bob Murray, taught me about rotary switches. Break before make is non-shorting. Make before break is shorting. The cumulative connection of contacts is sequence shorting.

Mr. Murray used his hands to illustrate what goes on. The index finger of 1 hand bouncing from finger tip to finger tip, for non-shorting. The index finger sliding from a tip into the gap between 2 tips and on to the 2nd tip, for shorting. The curved finger advancing along the tips, never loosing contact with a tip once connected, for sequence shorting.


Eli D.

 

RE: Ping: DAK, posted on June 24, 2017 at 23:33:19
Triode_Kingdom
Audiophile

Posts: 10042
Location: Central Texas
Joined: September 24, 2006
 Now that you say that, I do seem to remember seeing "sequentially shorting" many years ago, applied to rotary switches. Somewhere along the way, I must have erroneously associated "shorting" with that function. Do you know if there's a term for a switch that shorts all the contacts to common except the one at the selected position? Heathkit used wafers of that type in older selector switches to short unused inputs to ground. It's very effective at eliminating bleed-through.


 

RE: Ping: DAK, posted on June 25, 2017 at 00:34:54
SteveBrown
Audiophile

Posts: 2454
Location: Portland, OR
Joined: November 14, 2002
 I don't know what that's called but yeah, used to be used on selector switches to do things like ground all the inputs except the one you want. Cuts down on cross-talk I suppose. Some of those early selector switches were an engineering marvel, but also a service call just waiting to happen. Maybe one of the most useful tools of old TV Repairmen was a can of "Tuner Cleaner"!

 

RE: Thanx TK,, posted on June 25, 2017 at 15:14:18
DAK
Audiophile

Posts: 2712
Location: PACIFIC
Joined: August 8, 2010
 I have not gotten around to working on that issue yet. Per usual, life or wife, it doesn't seem to matter which, has intervened into my routine.

 

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