[AMRadio] Switch for GK 500A,B,C


Jim ars-w5jo at brightok.net
Sun Sep 13 15:56:56 EDT 2009


A while back I posted here looking for the Antenna Coupling Switch 
for my GK 500A.  One of the shorting fingers burned on it and 
another had been so hot that it lost contact with the wafer side. 
Several fine gentlemen had switches that they offered but none were 
indexed to the marks on the panel so I continued to look hoping that 
I could find one.

My search took me to MFJ parts via Ameritron.  In the GK 500 series 
the switch has 7 positions and the original was special order from 
Centralab series 231.  Electro Switch Corp. (electro-nc.com) has the 
rights to this particular switch and it is their E4 Series. 
However, none of the stock switches are made to progressively short 
6 positions.  They would build and supply what I needed for wafer 
replacement, cost ~$85.00.  The problems were I had to order through 
one of their retain sales outlets like Mouser, Allied, Digikey, etc. 
but the drive shaft for the wafer is now different.

Ameritron uses a two wafer band switch from Electro Switch model E4 
in their AL 1200 and 1500 amplifiers that would do the job.  The 
problem is the cost ~145.00.  Since I have owned this this King 
since 1994 and I received it from the original owner, I decided to 
go this route.  Installation is pretty straightforward, requiring 
you establish which position you want for #1 then moving the 
opposite stop one place farther down the line.  The switch is a 1 
pole 17 position switch and once you have decided which positions 
you will use, one jumper wire must be installed on the switch to 
make it work.

You have to remove the front wafer and only use the rear one that 
comes on the switch.  Then you have to cut the shaft to 1/2 inch 
length and the wafer drive appropriately.  This particular switch 
will short only 5 positions consecutively but there are two more 
shorting contacts located further around the wafer that can be made 
to give the needed 6 pole short.

So after Grand Ole UPS freight charges I have over $160 dollars 
spent.  But the switch looks and acts like the one that was there. 
Another reason for mentioning this switch is the same thing is used 
in the final tank to switch bands.  This is an expensive way to go, 
but I decided to do it to keep the radio as it was both electrically 
and operationally.  I guess I am happy now.

Jim/W5JO 



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