Roland JC60 AC power cable

[DrGonz78]

<<<This shows the ungrounded AC plug jack that L and N connect to from the main power cable.

Okay I have been sitting on this project for a while now waiting for reverse drill bits, but that is another story. Now that I have some pain in the butt screws removed I can finally get started. But first I need to understand how power reaches the transformer and onward.

So, I have provided some pictures to explain my trouble more clearly. Actually my true concern is that the AC power plug is only a 2-prong LN plug and not a 3-prong LNR. Lately, I have come across many amps where the safety ground is missing on the power cable and I simply replace the cable. However, with this amp there is no safety ground and that makes me nervous about how to trouble shoot the amp correctly. It almost appears that this is an isolated transformer design or someone was tinkering around w/ this amp. I don't think the power plug had been added this way and it appears that all the soldering is really original. The power switch has three settings and that makes sense in regards to the polarity of a plug that can be inserted both directions.

So the L is a white cable but on most amps I am working on L would be black. The black cable is the N and that is opposite to the respect of the right way to look at the power plug. Round green stamp would be the top of plug on the pictures and all the printed labeling would point in that direction. So, anyway just plug it in anyway it fits since N is not a fatter plug design. Does this make sense so far? Sorry if doesn't...

Any how look at these pictures and tell me how I can approach this design. Can I put a new 3-prong cable in place of the 2-prong power cable? If I do this which one is black or white in this case? Really confused right now so any help is good help... It has a star grounding system but only from the center tap of the transformer... Is that sufficient to read voltage from that grounded location? So many questions and too many thoughts, so please help me better understand what I should do. Thanks as usual in advance for everyone's help.

[Enzo]

Installing a three wire cord is easy, just wire the hot and neutral to the same old points and ground to chassis. The two wire plug was not polarized, so don't look for some pattern.

I don't care what color wires THEY used. It isn't about color, it is about function. This simple circuit has the incoming mains wired to the fuse then power switch and on to the transformer. Your incoming hot goes to the fuse, the incoming neutral goes to the other connection.

[DrGonz78]

Okay I figured as much here Enzo thanks for the clarification. Just was curious why they would design an amp w/ out the earth ground plugs.

[Enzo]

Your table lamp has no ground plug, and I bet your clock radio doesn;t either. LOTS of consumer electronics do not have grounded plugs.

[DrGonz78]

Sorry for being such Newb!! lol. I understand now more fully what a safety ground is doing. I read a bit more on the subject as to learn about safety grounds. Now I get that if neutral were to become detached then voltage can flow through the electrical unit enclosure etc... So now I finally have a better understanding that if neutral is somehow removed then there is still this extra ground feature to protect from voltage in the unit. Thanks again for dealing with my goofy questions.

[J M Fahey]

Plus, don't forget that amp is *old*.
Way back then 3 leg power plugs were not mandatory.
In the 40's no power transformer, straight to the power line chassis connections were acceptable.
Thanks God, safety perceptions improve along time.

[DrGonz78]

Yeah no kidding man. I was reading this quoted information on gearslutz where the guy said:

"Actually pretty simple. Remove the old cord. Install a three wire cord with proper strain relief. Green ground wire firmly grounded to the chassis, say with an eyelet connector fastened down to a bolt on the power transformer. Black (hot) wire to the inner connector on the fuse holder and from there (outer connector on fuse holder) to the power switch and then on to the transformer. Remove any "ground" switch and associated wiring. White (neutral) wire directly to transformer. Done."

I ask what he is referring to about removing any ground switch and associated wiring... Obviously forget about wire colors and concentrate on function as Enzo stated so eloquently. So looking at my amp I am working on is there any neutral grounds that need to be removed or anything safety wise that needs to be addressed. Or is it as simple as Enzo put it by adding just a cable and connecting correctly with added safety ground to chassis?

The link below involves really old 1950-1960's tube amps where the risk for higher voltage shock is much greater. I still would not want to be zapped by any amp and knock on non-conductive wood that never happens. It seems that back in the good ole days there were higher safety standards in many other countries than the US.

Old Amps or copy link "http://www.classicamps.com/oldamps.html]Old Amps"