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Disconnecting the Polarity Switch on a '73 Marshall

buddy7168

Gold Supporting Member
Messages
1,136
I’d like to disconnect the Polarity Switch and Death Cap from my ’73 Marshall. I’ve read a few threads that say as long as you have a three prong power cable (which I do) you can simply disconnect the Polarity Switch from the Power Switch. I noticed however that I have a light blue wire (from PT) as well as a yellow wire (from fuse) connected to the Polarity Switch. Do these need to be relocated and if so, where? Thanks in advance for your help!

Polarity Switch Close Up


In context
 

Steppin' Wolfe

Silver Supporting Member
Messages
5,788
You need to understand the path of the AC input wiring into and out of that circuit before taking on this job, imho. Nice amp...got a tech for it?
 

Jeff Gehring

Gold Supporting Member
Messages
6,797
If all you want to do is get the 'death' cap gone, just carefully snip ONLY the white jacketed lead from the cap that goes to the ground lug on the side wall of the chassis (don't cut the green/yellow and the black wire that also share that lug). Then take a common screwdriver and slide the blade between the cap body and the chassis and attempt to lever it free of the silicone or hot glue or whatever that is sticking it down. When the cap body is free to move, pull it out so you can then more easily snip ONLY the white jacketed lead coming from the other end of that cap that goes to the switch. Cut it right up at the switch lug it is soldered to, don't leave any leftover lead sticking out to potentially get into trouble. Take the cap out of there; job done.
 
Last edited:

buddy7168

Gold Supporting Member
Messages
1,136
If all you want to do is get the 'death' cap gone, just carefully snip ONLY the white jacketed lead from the cap that goes to the ground lug on the side wall of the chassis (don't cut the green/yellow and the black wire that also share that lug). Then take a common screwdriver and slide the blade between the cap body and the chassis and attempt to lever it free of the silicone or hot glue or whatever that is sticking it down. When the cap body is free to move, pull it out so you can then more easily snip ONLY the white jacketed lead coming from the other end of that cap that goes to the switch. Cut it right up at the switch lug it is soldered to, don't leave any leftover lead sticking out to potentially get into trouble. Take the cap out of there; job done.
Thanks! My main concern is to get the death cap out to make the amp safer. This seems like the simplest approach. Thanks again!
 

jcs

Member
Messages
8,093
If all you want to do is get the 'death' cap gone, just carefully snip ONLY the white jacketed lead from the cap that goes to the ground lug on the side wall of the chassis (don't cut the green/yellow and the black wire that also share that lug). Then take a common screwdriver and slide the blade between the cap body and the chassis and attempt to lever it free of the silicone or hot glue or whatever that is sticking it down. When the cap body is free to move, pull it out so you can then more easily snip ONLY the white jacketed lead coming from the other end of that cap that goes to the switch. Cut it right up at the switch lug it is soldered to, don't leave any leftover lead sticking out to potentially get into trouble. Take the cap out of there; job done.
Is that the same on my 71 Marshall Smallbox 50?
 

zenas

Member
Messages
8,872
With a proper ground the "death cap" is kind of a non issue. In the unlikely event that it does dead short and puts wall ac on the chassis, it goes to ground and pops the breaker in the fuse box.
I don't loose any sleep with them if the amp and outlets are grounded.
 

buddy7168

Gold Supporting Member
Messages
1,136
If all you want to do is get the 'death' cap gone, just carefully snip ONLY the white jacketed lead from the cap that goes to the ground lug on the side wall of the chassis (don't cut the green/yellow and the black wire that also share that lug). Then take a common screwdriver and slide the blade between the cap body and the chassis and attempt to lever it free of the silicone or hot glue or whatever that is sticking it down. When the cap body is free to move, pull it out so you can then more easily snip ONLY the white jacketed lead coming from the other end of that cap that goes to the switch. Cut it right up at the switch lug it is soldered to, don't leave any leftover lead sticking out to potentially get into trouble. Take the cap out of there; job done.
I did this and it worked perfectly. Thanks again for your help!
 






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