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Scott 340b powerswitch

James Cox

James Cox

AK Subscriber
Subscriber
Hi, i have a scott 340b that needs the power switch replaced. I found a switchcraft spdt switch but wanted to double check that it would work for my needs. Its rated at 125v but that seems low for a powerswitch. Will this work? If not what ratings should i be looking for on the switch? Also while we are here im also replacing the rectifier bridge and found a 3a 400v bridge, this should work right? Aside from the capacitors is there anything else i should swap out while im in there? Thanks
James
 
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I don't know what your level of electronic "savvy" is, but if you can manage it I would strongly suggest that you install a triac switching arrangement. That way the light-duty switch is merely controlling the triac, and the triac is controlling the heavy load.


triac-switch-circuit-basic-01.svg
 
See im not super savvy, more of a hobbiest for sure. This would only be my 5th piece ive brought back to life. I would definitely prefer a "plug and play" option without too.much modification. I know i should add a current limiter to preserve the switch but beyond that i dint really know how to go about installing a triac switching arrangement
 
Looks interesting but may be a little over my head. The switch is less than $2 that i found. May be worth the gamble to give ot a try
 
An inrush limiter is another way to reduce stress on the switch. Keystone (now Amphenol) CL-80 is rated for 3A, should help.

The bridge module is used for heaters and bias - 3A 400V will be fine. If it's silicon, I'd leave it alone. If selenium, you'll need to increase one or more resistors to get proper voltage.
 
Awesome, thanks man. I planned on getting an inrush limiter but wasnt exactly sure which ome to get. Ill get my parts order made and report back once i get this thing up and runnin! On a side not i already have a restored 299c and im interested to see if i hear a difference with the solid state rectifier vs the 5ar4 i have in the scott.
 
The really easy - half way - solution is to leave the 340B on, and just use a switch on a power strip for the on/off duty. The switch in the 340B still sees full current, but it doesn't actually switch, so less of the initial arc will be present. I run mine that way so that I can also turn on a cooling fan at the same time.
 
Ill probably do something like that after i put the new switch in but as of right now the switch is fried and the previous owner rigged it up with a switch on a very sketchy plug with lots of wires hanging out. My goal for now is to get this weird mod reversed and then try my best to keep the new switch alive haha
 
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