Help with rebuilding 700B db switch

Cryptopal

New Around These Parts
Joined
Nov 3, 2025
Messages
9
New member here, hello!
Recently paid $20 for a 700b. Not at all abused but a bit nicotine infused. Once on the bench I found that the 0 to -20db switch was missing.
Opening the unit someone had bagged the switch inside with what appears all the bits there. The 5 leads to it were clipped so I am sure no signal will pass without some sort of switch connected.
I'm looking for a replacement or someone who can reassemble the switch.
By the way what a discovery this forum is! Thanks to Joe at White Oak for the link!
 
So, it's not abused, it just has some parts missing? The round switches are impossible to find. There are many other ways to do a workaround for this issue (missing switch).




Clarostat 20.jpg
 
I found NOS Switches............

GET EM WHILE THEY ARE AVAILABLE

Flatted Shaft

--------------------------------------------------------------------------------------------------------------------

Back part of the switch where the wires hook up (I have about 10 NOS)

does not come with the shaft

------------------------------------------------------------------------------------------------------------------------------------
 
Last edited:
I found NOS Switches............

GET EM WHILE THEY ARE AVAILABLE

Flatted Shaft

--------------------------------------------------------------------------------------------------------------------

Back part of the switch where the wires hook up (I have about 10 NOS)

does not come with the shaft

------------------------------------------------------------------------------------------------------------------------------------
Wow thank you!
 
Just purchased the switch. I note there is a jumper soldered across 2 pins that will solve the issue.
Thank you!
Yep, just solder in the jumper and 3 wires, if you look on the back of the switch, it tells you it's a Clarostat 20, see it on your switch? It looks like your switch is 1 complete switch although it's probably busted. I've rebuilt a shit load of these and put them in all the wopl 700B's I built.
 
The part number of the back portion of the switch is Clarostat-20 and the shaft portion has its own switch control number and it depends on how you want the switch to be configured, such as a built-in volume pot or push/pull on/off. Those front shaft portion numbers are Ad-A-Switch SWE--20-DPST for our application but there are hundreds of wire wound resistors for customizing your switch. Or, order a complete switch like we did. Usually the front shaft portion goes bad from the set screw being too loose or from "Torque Em Tommy" reefing on the knob or being 40 years old
 
Once I get the switch installed I think I will use a variac and bring it up slow. I was told this one was in storage for a bit.
 
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