{Collins} Re: 516F-2 Question



Hi Everyone,

Thanks to all who replied to my question.

Here is a summary of  the replies I got. It may be helpful to other Collins
afficionados.

73 Chris ZS1DX

> I'm busy cleaning/fixing/recapping my 516F-2. The non-metal washer on top
of
> R5 has disintegrated, and the resistor is somewhat "loose". The manual
> describes this item as:
>
> "Washer, shldr, gra fbr, ..." Part number 1210
>
> What would a suitable replacement be? A homebrew asbestos washer, punched
> from an asbestos-type gasket material? Teflon? Any ideas?

ANSWERS:
--------------

the washer was used to stop the resistor rattling about but was pliable
enough to allow for compression as the resistor lengthened as it heated.a
washer made out of fibre similar to the old fibre washers used in taps will
do well.DO NOT USE TEFLON BECAUSE THAE GASSES IT EMITS WHEN HOT ARE VERY
POISONOUS.And asbestos will start to flake and will damage your lungs.kind

--------------

 have (6) 516F-2 units and all of them needed these washers.
So...hopefully I can help you out......

The nomenclature is....washer, shoulder, gray, fiber.
Hehe....just for the record..

I scoured the internet for the correct size and they just ain't out
there anymore.

As a temporary fix I cut small squares of thin, non copper clad printed
ckt board material.
This will last for awhile but not forever as the bleeder resistors get
quite hot.
Just drill a hole in each square and reassemble.

Later on, I did find some washers locally that did the trick; however,
they are still the wrong size.
I got around this by using 2 different size shldr washers at each
position...ie 4 washers on each resistor.
The 'inside' washer is a Waldom #FW-388 1/4" (i/d) screw size. The o/d
of the shoulder is .307 which is small enough to fit inside the resistor
i/d.

Next, the 2nd, smaller washer is a Waldom #FW-385, #6 (i/d) screw size.
The o/d of the shoulder is .217 which is small enough to fit inside the
FW-388 washer.

So, stack them up and fit the mounting bolt inside the assy and you are
good to go.

Just a word about those bolts....they are not just ANY bolt.
They are brass bolts (all thread) and as such are not very strong. You
can twist them off very easily. Don't apply much torque....remove
loctite when removing and more loctite (blue) on reassy.
Collins used brass all thread for these bolts due to close proximity of
eddy currents from the xfmr....these bolts could get quite hot if
conductive.
In addition, Collins scored the threads on at least one bolt (next to
bias pot) to prevent vibration from causing the bolt to fall out.
Typical USA Mil spec dont'cha know!

Whatever method you use, replace all the old washers while you are in
there.
I you don't.....you will later.

-----------------

I would machine one from Teflon stock. I think original was some sort of
fiber.

-----------------

Any fibrous washer should work.  It is used as a heat insulator on top of
the resistor.

-----------------


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