[Amps] LK-500 ZB problem

[Vic Rosenthal K2VCO]

Mike,

I can't answer most of your questions, but in general the most likely 
cause of vacuum relay failure is hot-switching. This could be due to the 
design of the amplifier, or the transceiver used to drive it.

K4MGS (Max Gain Systems) <http://www.mgs4u.com/index.html> often has 
suitable vacuum relays at reasonable prices.

On 5/28/2014 6:47 PM, mike stokes wrote:
> I bought a used Amp supply LK-500ZB.  Met the ham on his way to Dayton so I
> wasn't able to check it out beforehand.   So of course it has a problem.
>
>
> This amp has the QSK board with a qsk switch on the back.  All the
> schematics I have seen have 5 relays on the qsk board  while this one only
> has 3 relays.
>
> There is no continuity from the input to the output when powered off.
> Therefore no receive signal passes trough. Also the transmitter goes to
> high swr.  I know at a minimum that the  vacuum relay is bad.
>
> I have the following questions:
>
> Are the vacuum relays high failure ?
> Anything that typically causes them to fail.
> Any other thoughts as to what might be bad ?
> Does anybody have a schematic of the qsk board with only 3 relays ?
> Best place to buy a replacement vacuum relay ?
> Any other mods or thoughts while I am working on it ?
>
> Thanks in advance.
> Mike Stokes
> KK9V

-- 
73,

Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/