Tek 547: Ground? What Ground?

[scuzzyTerminator]

I have a Tek 547 stashed away where it can't easily be checked for awhile.

I was browsing a thread about using an isolation transformer for scopes (Bad Thing) and remembered that my old beast has a two prong plug with no earth. I had assumed it is the original equipment - I'm old enough to remember that it would have been hard to find an earthed oulet to plug it into in the early '60s.

So I'm wondering what the probe ground reference is supposed to be. Mains neutral? Floating?

[Jeroen3]

Did you check the manual what was delivered with the unit?

[bd139]

AFAIK they came with a 3 pin socket on the back so the earthyness is up to the user to work out. I remember in my short spell in industry, our scopes were ground strapped separately to the mains lead. They were somewhat newer than a 547 though.

[med6753]

Go back and look at your 547 again. I'm familiar with them and have never seen one that WASN'T a 3 prong plug.

Understand that these scopes were almost always in a lab environment. Labs were early to implement 3 wire grounding where as typical US residences built after WW2 and up until the early 1960's were not.   

[scuzzyTerminator]

Thanks for the replies. I thought someone might have a similar scope for a quick answer or check but it looks like I'll need to dig mine out. That will be awhile.

The power cord is two pronged and connects directly to the scope without a receptical. It is worn at the entry showing the two wires within. I had been thinking of replacing it with an earthed cord and assume that I could just put earth to chassis.

When I get it out I can check for conduction of chassis with probe ground and mains neutral.

This is a '60s model that I bought in the '80s.

Thanks again.

[David Hess]

My stock 547 has a three prong power connection.  So does my Lavoie LA-265A which is a clone of the Tektronix 545A.

[scuzzyTerminator]

Found manual at: http://w140.com/tek_547.pdf
I have a 1A4 plug-in: http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Tek/1a4.pdf

The videos at "Tektronix 547 (Tek 547) Oscilloscope Restoration":
https://lazyelectrons.wordpress.com/2018/07/06/tektronix-547-oscilloscope-restoration/
are way cool, But he clearly has a 3-pronger.