SCI Pro One fuse on Neutral Safe or not?

[AudioGimmer]

I’ve finally gotten around to working on my lovely SCI Pro One.
Aside from replacing all the rotten key bushings and cleaning up the J wires pots and switches, I noticed the original mains cable is starting to perish.
I also noticed the power switch is on the mains live, but the fuse is on the neutral line [which is also how it is on the schematic].

I’ve never seen a piece of gear with fuse on the neutral line. Is this safe or should I rewire it so the fuse is also on the live line?

Schematic attached:

Thanks

The Gimmer

 

[Speedskater]

Not safe!
In the US type 115/120V power system, both the switch and the fuse should always be in the Hot lead.

 

[AudioGimmer]

Yes, exactly what I thought, but it's odd that it was obviously built that way at the factory and that is how the schematic shows it.

 

[PRR]

> power switch is on the mains live, but the fuse is on the neutral line

Turn the plug over. Now the switch is on the neutral, the fuse is on live.

(Maybe you can't turn-over your UK plugs, but in the US we always could. 3-pin not a problem: if I can't find my 3-2 adapter, I got cutters.)

Even if the cord is wired Known Way, the wall-outlet can't be trusted. (60% wrong in my last kitchen; UK electricians may have much better record.)

At the time this was built, this wiring was perfectly correct *inside the chassis*. It is a cord-connected appliance. If you must put your finger inside, UN-PLUG IT!! Now the fuse is NOT connected to ANYthing.

(Do not confuse this with the rule about building fuse-panels. Building wiring can not be un-plugged, and it may not be possible to disconnect all loads. Hence we do not fuse Neutrals in fuse-boxes. But that's a different situation.)

If you put your finger inside AND have it plugged in, that's your responsibility. And there are probably many other danger-points.

> obviously built that way at the factory

If you didn't have that voltage-selector: this IS the way to do it. The power cord and the PT leads all have places to "land", no wire-splices needed. Very neat and elegant.

 

[AudioGimmer]

Thanks PRR

We can’t turn our plugs over, but since I am going to replace the line cord as it is perished, I could wire it that way internally: Live to fuse and the switch on Neutral. But then again, since I have to rewire it anyway maybe I should just make the switch and fuse on Live and be done with it.

The Gimmer

 

[audiomixer]

Switch, fuse and Transformer are all wired in series, so it really dos not matter.  Fuse is for overcurrent protection and will work ok there. Neutral is not involved in safety,  thats what the Earth Pin is for.

- Michael

 

[abbey road d enfer]

Switch, fuse and Transformer are all wired in series, so it really dos not matter.

If it didn't really matter, the safety regulations of many countries (US, Canada, UK, FRance, Switzerland, Germany, Korea, Japan...) would not insist on the "fuse-and-switch-in-the-live-connection".

 

[AudioGimmer]

Yes, I think I'll play it safe and rewire it with switch and fuse on the live line.

Thanks all.

 

[PRR]

> US, Canada ... would not insist on the "fuse-and-switch-in-the-live-connection".

I'm not aware of that rule in the US *inside the appliance*.

German plugs can be turned-over.

If in doubt, install a DOUBLE-POLE switch and break both live conductors. (This IS required some places, and may eventually become Global Practice.)

 

[abbey road d enfer]

> US, Canada ... would not insist on the "fuse-and-switch-in-the-live-connection".

I'm not aware of that rule in the US *inside the appliance*.

That is one of the first things the consultant I had hired checked when I started selling stuff in the US ca. 1982, though. It may not have been mandatory, but since it was in many countries, that was how it was done, so I didn't really question the legality.

German plugs can be turned-over.

In France, they can't; however many socket strips alternate right and wrong (angled at 10.30 and 7.30).

 

[zebra50]

Of course here in blighty we have a fuse on live in the plug anyway.

Stewart

 

[abbey road d enfer]

Of course here in blighty we have a fuse on live in the plug anyway.

Stewart

Yes, I noticed that. But it does not seem to free you from the necessity of an internal fuse, does it? I believe the fuses in the plug are rated 13 Amp...?

 

[s2udio]

Yes, I noticed that. But it does not seem to free you from the necessity of an internal fuse, does it? I believe the fuses in the plug are rated 13 Amp...?

By current UK IEE regs the equipment must have an appropriate plug top fuse for the rated Full Load equipment current,
IE 2A,3A,5A,10A,13A, this applies to the current IEE regs when PAT testing, which has to be done for all industrial,business
Premises once every year.....with exceptions.
However Joe Average will just stick a 13A in there......or as I have seen before, A nail or Tin Foil !
The UK equipment standards (CE) also state the equipment internal mains fusing to be in the LIVE conductor
Before the DOUBLE POLE (L+N) switch.
Our neutral or "return" AC path is  in all modern installations referred to as PME, or Protective Multiple Earthing,
The Earth is a secondary parallel path bonded to neutral at the consumer unit, again with exceptions in old Overhead wire installations.

 

[abbey road d enfer]

IE 2A,3A,5A,10A,13A, this applies to the current IEE regs when PAT testing, which has to be done for all industrial,business
Premises once every year.....with exceptions.

How do they manage sochet strips?

The UK equipment standards (CE) also state the equipment internal mains fusing to be in the LIVE conductor

That is perfectly clear.

Before the DOUBLE POLE (L+N) switch.

If I remember well, this was for equipment drawing more than x?VA. I have sold a LOT of stuff in the UK and never have been challenged on that point, but all mys stuff was less than 100VA.

Our neutral or "return" AC path is  in all modern installations referred to as PME, or Protective Multiple Earthing,
The Earth is a secondary parallel path bonded to neutral at the consumer unit, again with exceptions in old Overhead wire installations.

Yes, TN-C-S, according to IEC nomenclature. Saves some copper.