[Collins] 51J4 Crystal Filter

[Al Parker]

Hi John,
	If you can see the capacitor(s), read the value of it.  Go to:
<http://www.wiktel.com/standards/capa.htm> for info on how.  75pf might 
be right, or close, but it's easy to ck.   (my skem doesn't show valurs 
there either.)
	Does the alignment peak when you adjust either?  If so, they're 
probably OK.  But, micas, especially those small one, are being found 
leaky more and more now.  I'm presently working on a Collins R-390/URR 
that has had 4 bad ones in it (so far), and one resistor that was fully 
open, no signs of everheating or physical damage.  One of the caps 
showed about 25k resistance even at the 9vdc that the Fluke puts on it, 
the others were OK on the Fluke, but when ckd on the bench megger, they 
started showing resistance at 50vdc or so.
	This xtal phasing stage has no gain, actually has some loss, so don't 
expect signals to get stronger thru it.
	hope this helps some,
73,
	
Al, W8UT
www.boatanchors.org
www.hammarlund.info

"There is nothing -- absolutely nothing -- half so much
worth doing as simply messing about in boats"
Ratty, to Mole

On 9/24/2011 9:18 AM, Jon L. Turner wrote:
> Hello All,
>
> I am going through T101 and T102 on a 51J4 that I purchased. I am wondering if anyone knows the value of the capacitors inside the cans. My tester shows 75 pf on the one in T101. I am not seeing a value on them in the schematic. The receiver seems to be low on sensitivity and it is looking like it is in this area of the receiver.
>
> Thank you,
>
> JT