[ARC5] TCS RF ammeter or thermocouple replacement

[J. Forster]

Most of the RF Ammeters I've seen are built like this:

              ANT
   m--------\  |
   e         \ |
   t          O|
   e         / |
   r--------/  |
              TX

The wire connecting the Tx to the Ant is resistive. If there is low
resistance, it's probably OK.

That wire is thermally connected to the TC with a lob of goop (cement).

The TC is made of a welded junction of two dissimilar metals.

Since the subject meter does work, the Tx-Ant has to be continuous and so
does the TC and meter circuit.

That leaves two possible problems:

The meter magnetic field may be way down. Test the meter w/o the TC connected
or
The TC has become improperly bonded to the heater wire. This is a delicate
operation, but I suspect a small drop of RTV or epoxy might cure the
problem.

FWIW,

-John

===================


















> On 25 May 2011 at 17:54, Henry Frederick "Meils" Meiseles wrote:
>
>> I haven't opened the meter yet to take a closer look at the how the
>> thermocouple is mounted -
>> I assume that once a thermocouple is overloaded, it's not reparable.
>
> That is not true: they are repairable, but with some difficulty.
>
> There was a very detailed article, written by an Australian, if I remember
> correctly,
> in a somewhat recent issue of Electric Radio magazine, in which the author
> restored several RF ammeters, using a home-made device. He then calibrated
> them, and unless there was some other mechanical problem with the meters,
> his
> success rate was very high.
>
> If you cannot find a reference to that article on the ER website, I will
> attempt to
> find it in my messy collection of ERs.
>
> Go here:
>
> http://www.ermag.com/
>
> and here:
>
> http://www.radiolabworks.com/ersearch.html
>
> Ken W7EKB
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