Replacing Two Prong Power Cable in Effects Pedal

[Paul in Colorado]

I have an old Morley Volume Pedal that needs to have it's power cable replaced. The old cable is a non-polarized two prong and I'm replacing it with a three prong. I can ground the case using a tab on the transfomer bolt, but does it matter how I wire the power connections? I just want to make sure it's done right and safe. Other then that, getting the strain relief out and a new one in looks to be the hardest part!

[mofugly13]

If the wires on the line side of the transformer are two different colors, then you want to go white to white, and blacl(on the new cord) to the other wire. If both wires are the same color at the transformer, then it doesnt matter.

[Paul in Colorado]

There's one problem. On the new cable instead of black and white, the colors are brown (wide prong) blue (narrow prong) and green/yellow (ground). The new cable is a computer-type power cable that I cut the female end off of. What would colors correspond to black and white?

[RodeoTex]

This thread is scaring me. Please take it to an electrical repairman.

[Paul in Colorado]

Originally Posted by RodeoTex

This thread is scaring me. Please take it to an electrical repairman.

There are three wires. One is obviously ground. There is a "big" prong and a "small" prong. Which one would be black and which would be white? I'm just making sure I have the right wires on the right terminal. Doesn't seem too scary to me. Why computer type cables have different colors is beyond me. The current condition of the pedal, a two prong cable that can be plugged in any way you want that's getting freyed at the strain relief, is what scares me!

[RodeoTex]

Not scary actually but there's a few things to watch for.
You are right in using a xfrm mounting bolt the gn/yel. It might be a real good idea to use an ohm meter to verify that neither input tap of the transformer is internally grounded. If not then it the placement of the brown and blue don't matter.

In my experience the brown is used for hot and blue for neutral. This isn't just a computer thing or something new. The bn-be-gr/yel cord is a long established European standard and in my experience the blue is neutral (wide prong).

Now you've got me curious. I'm going to have to cut up a computer power cord this afternoon and see which wire they've got on the wide prong.
I do know for certain that U.S. standard code wiring the neutral wire is connected to the wide prong in the receptacle.

Best of luck to ya.

[Paul in Colorado]

Thanks, Rodeo Tex!

I'm asking because I want to be safe. I have a healthy respect for electricity and want it to be right. Checking the transformer for ground is a good idea too.

The circuit is pretty simple. Basically, the AC goes to a transformer that drops the voltage to less then 12 VDC to power a light bulb. The Guitar circuit goes to a photo resistor and back out. There is a shade that covers the photo resistor varying degrees as you press down on the treadle. Shaded is off, open is full on.

[Paul in Colorado]

Well, I put it all back together with the new cable and strain relief and all is well. I checked and double checked my connections, checked for stray voltages after plugging it in and fireing it up. All is well! It's a good feeling to do something you've never done before and have it work right the first time.