Re: RM503 ongoing repair saga T620 UNWOUND.


Chuck Harris <cfharris@...>
 

Ok, there was a request for some measurements:

First, the primary of a 547 style transformer is wound:
#1.....#2.......#3
0 ---- 20T ---- 60T


It is universal wound with #38 gauge bifilar, parallel connected.

I tested 3 transformers. One of my manufacture, one known to
have the transformer epoxy disease, and one believed not to have
the disease (but unverified by me).

The first series of tests was done with a Sencore LC-102, and all
possible connections to the primary. The second test was done
using a GR-1650B LCR bridge. I only tested the full primary (1,3)
with the GR bridge, and it was tested at 1KHz.

My transformer:

Sencore:
1,3... 60T... 74 rings.... 1.22mH
1,2... 20T... 58 rings.... 158uH
2,3... 40T... 66 rings.... 395uH

GR:
1,3... 60T... 1.68mH, Q=2.15

Thought to be good original:

Sencore:
1,3... 60T... 50 rings.... 1.884mH
1,2... 20T... 35 rings.... 140.3uH
2,3... 40T... 42 rings.... 756uH

GR:
1,3... 60T... 1.94mH, Q=2.8

Known diseased original:

Sencore:
1,3... 60T... 51 rings.... 1.562mH
1,2... 20T... 37 rings.... 128.6uH
2,3... 40T... 46 rings.... 604uH

GR:
1,3... 60T... 1.76mH, Q=2.2

Bear in mind that the Sencore uses a rather different method of
measuring inductance. It applies a voltage source to the inductor
through a resistor, and times how long it takes for the inductor's
voltage to reach some specified value.

And,

The GR bridge is measuring at 1KHz, which is not the design frequency,
nor the frequency I measured the Q at using the Boonton Q meter.

The differences in inductance are probably due mostly to gap tolerance.
The "known diseased original" transformer was tested cold, so it
should not be too surprising that it tests about the same as the rest,
as it works fine when cold.

-Chuck Harris

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