Preamp B+ Voltage High/Low Switch?

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FourT6and2
Posts: 244
Joined: Wed May 31, 2017 11:11 pm

Re: Preamp B+ Voltage High/Low Switch?

Post by FourT6and2 »

martin manning wrote: Tue May 27, 2025 3:15 pm
FourT6and2 wrote: Tue May 27, 2025 2:30 pm My only concern is that the switch will have 400v+ DC across it if I do this.
Vp / Screen voltage = 513v
With both 10K resistors (20K total), that drops to 344v. So bypassing one with the switch will send a good amount across it.
513-344=169
169/2=84.5

That's the voltage across the switch when it's open. Yes it will have 513-84.5=428.5V potential on it, but its dielectric strength should easily handle that.
That's all I need to hear, thank you.

Now I just need to figure out how to move all the wires on the polarity switch elsewhere. Death cap already disconnected, but whoever did that didn't rewire the mains to fuse hot. So I gotta figure out how to do that without digging into the factory wiring harness/lacing too badly.
FourT6and2
Posts: 244
Joined: Wed May 31, 2017 11:11 pm

Re: Preamp B+ Voltage High/Low Switch?

Post by FourT6and2 »

Actually, it's already wired to fuse the hot. I just need to move the connections off the polarity switch. Before/after. Think this should work?
Before.jpg
After.jpg
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martin manning
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Re: Preamp B+ Voltage High/Low Switch?

Post by martin manning »

If your ? are confirmed it looks fine.
FourT6and2
Posts: 244
Joined: Wed May 31, 2017 11:11 pm

Re: Preamp B+ Voltage High/Low Switch?

Post by FourT6and2 »

martin manning wrote: Tue May 27, 2025 11:34 pm If your ? are confirmed it looks fine.
Yes sir, thank you!
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