Orientation for the non polarized plug in vintage audio

[pollock0424]

Note that the whole thing is enclosed in a wooden container..

Should I plug the fused size into neutral ? This way, if C5 goes death cap on me then the neutral will come in direct contact with the aluminum chassis..

Switched side will be connected to the live, if the C6 goes death cap then I'm out of luck!

The only safe way to use this without modifications seems to be to use a truly isolating transformer (including gnd/earth isolation). This way, i will not have a gnd reference fault..

Unit is all Germanium so chasis is the positive...

Reference ends of C6 and C5 have connectivity..

Looking to seek advice from seasoned techs and electricians..

 

[egellings]

I would want the hot lead from the plug connected to the fuse in the power supply. Modern 2-prong plugs have one blade wider than the other to force insertion into the outlet in the same direction always. The thinner blade is the hot one, while the wider blade is neutral. In the US, the black colored lead of a cord is hot, and the white lead is neutral. If a 3-prong plug is used, the added green, or green with yellow striping lead, is earth ground. If your cord has a plug with identical width blades allowing insertion in either direction, it would be a good idea to replace the non-polarized plug with a polarized one for safety's sake.

 

[Gibsonian]

I plug em in whichever way is the quietest. Not worried about shock here, all SQ

 

[egellings]

I plug em in whichever way is the quietest. Not worried about shock here, all SQ

Until you get shocked, you won't worry about it. After that event, if it ever happens (hope not!), I'll bet your attitude will change. I really don't like personally conducting electricity, myself.

 

[G|force]

What I always used to do was try both ways with a DMM set to VAC and probe between an RCA shell on the gear and the outlet ground. Use the orientation that shows the lowest reading.
There is usually a significant difference.

 

[pollock0424]

What I always used to do was try both ways with a DMM set to VAC and probe between an RCA shell on the gear and the outlet ground. Use the orientation that shows the lowest reading.
There is usually a significant difference.

I tried this, if I plug the fused side into neutral I get the lowest AC voltage (~40V). I even touched the chasis with the back of my finger and no tingling feeling. The other option gives ~55V and I didn't dare touching it.

 

[pollock0424]

I would want the hot lead from the plug connected to the fuse in the power supply. Modern 2-prong plugs have one blade wider than the other to force insertion into the outlet in the same direction always. The thinner blade is the hot one, while the wider blade is neutral. In the US, the black colored lead of a cord is hot, and the white lead is neutral. If a 3-prong plug is used, the added green, or green with yellow striping lead, is earth ground. If your cord has a plug with identical width blades allowing insertion in either direction, it would be a good idea to replace the non-polarized plug with a polarized one for safety's sake.

If I want to keep it stock, does the isolation transformer make it the second best solution?

 

[pollock0424]

I plug em in whichever way is the quietest. Not worried about shock here, all SQ

Sorry, I will not do this. If I want SQ then there are better options..

 

[G|force]

I tried this, if I plug the fused side into neutral I get the lowest AC voltage (~40V). I even touched the chasis with the back of my finger and no tingling feeling. The other option gives ~55V and I didn't dare touching it.

That sounds odd. Is there any potential between neutral and ground? I'm wondering if the load center is properly bonded and the receptacle is wired correctly.

 

[egellings]

Check that the electrical outlet is correctly wired.

 

[Gibsonian]

Until you get shocked, you won't worry about it. After that event, if it ever happens (hope not!), I'll bet your attitude will change. I really don't like personally conducting electricity, myself.

I’m 60. Of course I’ve been shocked before. Never have been listening to vintage audio though no matter which way I plugged in the device. I’ve never spoken with anyone whomever did nor do I worry about all the ungrounded two prong modern devices still out there.

 

[pollock0424]

That sounds odd. Is there any potential between neutral and ground? I'm wondering if the load center is properly bonded and the receptacle is wired correctly.

Just checked and no potential difference between GND and neutral.

 

[pollock0424]

Notice the secondary side of the transformer.. center tap going to the chasis..

 

[marin.weigel]

Notice the secondary side of the transformer.. center tap going to the chasis..

No, it's + actually, check the legend above the schematic.

 

[marin.weigel]

... if C5 goes death cap ...
... if the C6 goes death cap ...

Can you show a photo of these caps, preferably with imprint?

If you're scared, replace with 4.7nF EMI suppressor, class Y2, metallized polypropylene caps, which are made to sustain tests at 5000 VDC and 2500 VAC, like Kemet PHE850EA4470MA03R17

 

[pollock0424]

No, it's + actually, check the legend above the schematic.

Chasis gnd is same as positive in this case. There's connectivity between +ve of C1 and the grounded side of C5 and are tied to metal chasis.

 

[pollock0424]

Can you show a photo of these caps, preferably with imprint?

If you're scared, replace with 4.7nF EMI suppressor, class Y2, metallized polypropylene caps, which are made to sustain tests at 5000 VDC and 2500 VAC, like Kemet PHE850EA4470MA03R17

 

[marin.weigel]

Chasis gnd is same as positive in this case. There's connectivity between +ve of C1 and the grounded side of C5 and are tied to metal chasis.

Strange, they're using different designators though, oh well.

 

[marin.weigel]

Those seem to be ceramic discs, I'd be surprised, if they'd ever short on failure.

 

[pollock0424]

Those seem to be ceramic discs, I'd be surprised, if they'd ever short on failure.

Do you want me to leave them alone ? Surprising fact about the sealed PS caps in this amp is that they were still in spec!!!! After 60 years, they had very low esr (0.5ohms) and within 20% on the upper end. All other lytics showed higher esr and drift...