Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => AmpTools/Tech Tips => Topic started by: jordan86 on December 01, 2020, 04:54:35 pm

Title: "Correct" fuse and switch wiring for 3 prong
Post by: jordan86 on December 01, 2020, 04:54:35 pm

I replaced the 2 prong AC cord in my 65 Showman recently with a grounded 3 prong, bypassing the ground switch and death cap. I took the "simplest" path based on the stock wiring.  Example A below. It allowed to not remove any more wiring than necessary based on the way the PT was originally wired. Wondering if Example B would be better, safer, more up to modern "standards". I'm no electrician :)

Ex. A is actually how I wired my first amp build (AA1164) based on the Mojotone Kit instructions, so I presume it's not too unsafe.

Title: Re: "Correct" fuse and switch wiring for 3 prong
Post by: sluckey on December 01, 2020, 05:13:11 pm

"B" is preferred. The important thing is that you have the green wire from your power cord securely connected to chassis.

I would replace that two prong convenience outlet with a "proper" three prong outlet or just disconnect it. I think user "p2pAmps" has found a source for a 3-prong outlet that fits.

Title: Re: "Correct" fuse and switch wiring for 3 prong
Post by: jordan86 on December 01, 2020, 05:57:50 pm

Thanks, Sluckey. Yes, ground wire is definitely secured on chassis. Again, left the hot/neutral in the "sort of stock" scenario to minimize changing too much on the old amp. I have no intention of actually using the convenience outlet. It was more so about not moving the primarily side leads on the transformer.

I take "preferred" to mean it works fine as is? No major red flags?

Title: Re: "Correct" fuse and switch wiring for 3 prong
Post by: PRR on December 01, 2020, 09:27:20 pm

> it works fine as is?

Inside the appliance chassis, it does not matter.

You NEVER know which prong is "live". (There is a right way to wire a wall outlet, but 6 out of 10 outlets in my kitchen were wrong, and the US average is not a lot better.)

You can always get shocked changing the fuse (a popular objection), unless you go to a DP switch (almost unknown in America). UNPLUG before changing fuse--- most appliance safety rules are based on PLUG CONNECTION and total isolation after a 2-second disconnect.

Title: Re: "Correct" fuse and switch wiring for 3 prong
Post by: Latole on December 02, 2020, 03:30:58 am

Answer ; B

Always fuse and switch the hot side
Il put fuse before the switch.

I'll remove death cap

Title: Re: "Correct" fuse and switch wiring for 3 prong
Post by: jordan86 on December 02, 2020, 10:34:38 am

Quote from: PRR on December 01, 2020, 09:27:20 pm

You can always get shocked changing the fuse (a popular objection)

Yes, this was the one concern on my mind. Changing the fuse while plugged into the wall. Just didn't know if there were others. I think I am content to run that risk myself for the time being, but I definitely want to revisit it. Especially if I ever sell.

Thanks guys!

Title: Re: "Correct" fuse and switch wiring for 3 prong
Post by: sluckey on December 02, 2020, 11:13:53 am

You can reduce the risk of shock by connecting the hot line wire to the end lug of the fuse holder, never to the side lug. Like this...

     http://sluckeyamps.com/misc/AA864_Musings.pdf