[Premium-Rx] Cleaning RF cavities.

[John Wilson]

Now that is a truly helpful posting. Many thanks Richard, in anticipation of
the awful day when I will have to face my own 8640s, fortunately working
perfectly so far. Mind you, whilst I know what "Silver Dip" is, perhaps it's
not easily available under that name over in the US.
Regards
John Wilson

-----Original Message-----
From: premium-rx-bounces at ml.skirrow.org
[mailto:premium-rx-bounces at ml.skirrow.org]On Behalf Of Richard Reich
Sent: 17 March 2003 10:38
To: premium-rx at ml.skirrow.org
Subject: [Premium-Rx] Cleaning RF cavities.


Hello List.
I have been involved in refurbishing high-power television transmitter, and
microwave link, cavities - and the practices used here may be of help to
others.
The cavities and sliding fingers are usually silver plated. Do not be
tempted to
use any sort of abrasive paper, or metal polish. Quite apart from the
damaging
abbrasive nature - the polish always leaves behind some sort of residue
which
gives more problems later. For cleaning we used a silver replacement
solution
called "Silver Dip' made by Goddards - and the items are dipped/immersed in
it.
Simply put, this re-converts the silver oxide back into silver - like
currentless electro-plating. Failing the use of Silver Dip, just clean
thoroughly and vigorously with very mild detergent and water using plenty of
elbow - then dry out in an oven system. Where you have corrosion - this will
need to be abraded, polished, and re-plated using Silver Dip. One common
problem
is wear on cavity fingers - if there are flats appearing, problems are in
the
wings. The cavities themselves are never lubricated with anything. One of
the
worst lubricants in electronics is WD40 - it dries to form an insulating
film -
and will certainly stuff the efficiency of a cavity, and is very difficult
to
remove afterwards. One safety note - spring fingers are usually made of
Berillium Copper - whether silver plated or not - the fine copper dust
release
through wear is a carcenogen - so take care. Hope this helps.
***************************************************************
Richard Reich
Principal Engineer Hardware
SAAT Technology Ltd
Web: http://www.saatt.co.uk

DDI: +44(0)1420 545388
Fax: +44(0)1420 87259

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