[Amps] LK 500 ZA bandswitch

[jeremy-ca]

Mouser can get you a new switch for $226 ! I just bought one for a customer 
repair. Part # is E4C0408N and neither Mouser or Electroswitch was 
interested in supplying just a wafer.

The problem is not the fixed caps, Ive never seen one go, even tho the same 
ones are used in the 2500W LK-800A.

Look at the switch and you will see that there is almost no spacing between 
the solder terminals and the metal hardware. A little bit of mistuning and 
ZAP. If the Tune cap has also been arcing that is another indication of 
serious mistuning.

The contacts themselves are staked in place. Its easy to drill out but once 
a serious carbon path has developed it is there to stay. The switch I 
replaced was so bad that the end where the threaded rod goes thru was eaten 
away.
Replacing with an unused contact will also require trying to hold in place 
with a hard solder. IMO its a short term solution as the switching will 
eventually loosen it up.

When installing a new switch or wafer use a fiberglass, Delrin or similar 
nut and no washer. Epoxy an insulating material between the solder contact 
and the nut. I use a hunk of old PC board with no copper on it.

The Tune cap is a bolt together job, I have replacement plates.

Carl
KM1H




----- Original Message ----- 
From: "dave arruzza" <w1ctn at yahoo.com>
To: <amps at contesting.com>
Sent: Thursday, October 25, 2007 2:22 PM
Subject: [Amps] LK 500 ZA bandswitch


> Hello all...
>  Has anyone found a replacement bandswitch for this amp?
>
>  Once while talking to Bill @ Omega Electronics he told me his was 
> drilling out the rivets on old bandswitches he had and retrofitting the 
> switches with new contact shoes.
>
>  Sounds labor intensive, but do-able. Does anyone on the list know where 
> you can purchase new contact shoes and the matching rivets? Or maybe you 
> can just use screws.
>
>  The bandswitch, and a few other parts, are minimal. I think my bandswitch 
> arced due to the padder caps, (C33, C34 and C35)  going south.
>
>  No output on 160/80/40. Ok on 20/15/10, where there are no padders 
> switched in.
>
>  But thats just a hunch. Seems kind of odd to put disk caps in that 
> environment.
>
>  My switch has a cooked contact or two and I need to get it repaired. I 
> tried calling Omega and just got voice mail.
>
>  73
>  Dave W1CTN
>  Now Low Power in CQWW....
>
>
>
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