Re: 577 AC collector supply not reading zero on display

k1ggi
 

Google US patent 2,009,013.
It was a case study in a course in an engineering curriculum, taught by R.H.
Rines, son of the patent attorney.
Yes, Rines of Nessie fame.
Ed, k1ggi

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Roy
Morgan
Sent: Tuesday, December 10, 2019 3:00 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 577 AC collector supply not reading zero on display

I have seen Variac brushes that were not point shaped at the contact but
rather had s linear shape. The contact end was as long as the brush diameter
but narrowed along the sides so as to contact the full length of the
flattened portion of one or two windings.

Without examining any of the ones here, I suspect they do contact more than
one winding if positioned between two wires in order to create smooth
transition from one winding to the next.

I do have one very old GR Variac whose brush is simply round, and is flat on
the contact end. It may date from the 40's or even 30's.

Roy sends.

On Dec 9, 2019, at 10:57 PM, DW <wilson2115@...> wrote:

What you describe makes sense Chuck. I observe no issues with smoke, hum,
and the variac works throughout its full operating range other than not
going to zero. Therefore I been convinced the variac as far as the winding
is fine.

Having ruled out the variac, Bob made a good point about the carbon brush,
I believe he is on to something about the contact point being worn down
widening the contact area and potentially causing what I am experiencing. I
will try to rework the brush to a point with some sand paper and see if I
notice any improvements.

I would like to thank everyone here for their valuable help, I see this
being useful for someone with collector supply issues to check the wiper
brush!


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