[Test-Equipment] Bird Termaline Question - Update (long)

[Brian]

Hello Howard,

That circular clamp adds diameter to the tubular resistor. The conic section 
dimension at that point directly affects the impedance. Your measurement of 
49 Ohm is not so important as the impedance - how about measuring that at a 
few different frequencies?

I have had similar problems with cracked tubular resistors for use in 
oil-cooled dummy loads. My solution was to infiltrate the crack with a 
silver-loaded Araldite (R), the type auto electricians use to repair the 
elements in heated windscreens that have been damaged by women scraping 
their diamond-encrusted fingers over the screen to remove condensation. I 
achieved the nominal resistance and there was no observable effect on 
impedance.

73 de Brian, VK2GCE.

On Wednesday, February 08, 2017 6:35 AM, you said:

Back around 1962 or so, I came by a 500 watt Bird Termaline load.
According to an ohmmeter, it was reading high - well over 50 ohms but
less than 100. I do not remember exactly what it was.

I stood the load on it's back end, loosened the clamp ring and removed
it from the case. Lost a little oil in the process. The problem was a
crack in the load resistor up near the top or feed point end. Since the
coating on the resistor was conductive, I put a small stainless radiator
clamp (about 1/2" wide) over the crack and tightened it. The resistance
went to about 49 ohms or so and I put it back together with a little
additional mineral oil. I still have that load and it is still working.
The slightly low resistance doesn't make any practical difference in the
normal use of it.

Howard K5JCP in GA