[Amps] More LK500

[Ian White GM3SEK]

Jeff Strailey wrote:
>My problem with operating an LK500 following the change to 120 Vac 
>operation appears to be related to a step start mod that was added at 
>some time to the amplifier.  Perhaps someone has a schematic or other 
>information regarding a step start mod kit that was sold at some time 
>for the LK500.  It is tempting to simply remove it and restore the AC 
>input side of the amplifier to it's original state but step start is 
>desirable if it can be made to work.

It looks like your low B+ problem is because the step start relay is not 
pulling in. This means that the resistor is permanently in series with 
the mains... and will be having a very hard time.

Don't remove the step start! It was added to protect the transformer, 
electrolytics and tubes, which was something the manufacturer should 
have done.

It should be no big deal to make it work on 115V AC. Depending on the 
circuit, you may need to change the voltage-dropping resistor in series 
with the relay coil, but that's probably about all.



-- 
73 from Ian GM3SEK         'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek