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I work the FT-243 Xtals and similars with ammonical
bifluoride acid (FH-FNH4), much less aggressive that the fluorhydric acid
(FH)
I utilize two disolutions marked as 5khz/10_min and
1,5khz/30_min. This is a reference, therefore each Xtal takes the velocity that
desires him.
At each one, must do attack velocity test.
When you approach the frequency desired, the bath should be of more short term
and whit measurement.
To bathe the Xtal, I utilize pincers of revealed
photographics, wing that have carried out channels filed near the tip for take
the Xtal so that the flat faces remain free for the attack of the
acid.
My record of variation of a Xtal of 8 mhz is 403
khz obtaineds in 10 days of baths.
8.377 to 8.780,8 => 137,200
If we have passed ourselves in frequency, at
Xtal "injured", applies him itsel, "mercury-chrome" whit a human air.
( Edding pen?)
If the bath, as been long-term, is possible that
the Xtal to stop oscilating. In this case, to smooth the surface, I
utilize abrasive paste of "corindon-corundum". Also is worth te
dentifrice-paste. As base of support, I
utilize a piece of flat glass.
The flask of the disolutions should be of special
plastic for chemitry. The fluorhydric acids (also the bifluoride), they
attack the glass.
A 20% of my Xtals they have died in the operation,
well because in the in the maneuvers of dismantling-assemblyng, they have broken
itself or because to stop oscillating and there is not form to resurrect
them.
Each time that there is a session of bath, one must
wash the Xtal with soap and running water and to dry it with absorbent
paper.
A lot of attention, therefore we are working with
higly corrosive material.
Federico EA2HB
----- Original Message -----
Sent: Saturday, August 19, 2006 10:38
PM
Subject: Re: LF: TIP: modifiying
X-tals
In the ol days we would use a pencil or rub a bit of solder on the
face
real hams used ? acid to etch and raise the frequency,, I dont
remember
what the acid was but the local chemical company would sell a
bit
drill a hole in the mount face, tap it and use a screw to apply
pressure and move the frequency around
Bob K3DJC
For those who didn't know, use following
'trick' to tune your own X-tal. (found it in a magazine from the
VERON)
Take an permant marker pen ("Edding, or
similar) and put a little stripe/line on the X-tal plate.
You will notice that the frequency goes down a
bit.
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