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Re: [Amps] LK-500 problem

To: vk6apk@eon.net.au
Subject: Re: [Amps] LK-500 problem
From: Gudguyham@aol.com
Date: Mon, 29 May 2006 06:49:27 EDT
List-post: <mailto:amps@contesting.com>
 
In a message dated 5/29/2006 6:08:13 A.M. Eastern Standard Time,  
vk6apk@eon.net.au writes:

>I  recently obtained an Amp Supply LK-500ZB.  The first order of business  
>was the conversion to 120 volt operation.  When the amp is  powered plate 
>voltage as measured by the internal meter is about 1500  volts instead of 
>the 3100-3300 vdc one would expect.  I've  attempted no troubleshooting 
>whatsoever as of yet but wonder what  could be going on?  One or more 
>electrolytics or diodes bad in  the power supply?  Obviously I will need to 
>examine the power  supply but am just wondering if anyone has seen 
>something like this  before in this or a similiar product?
>



It is doubtful that the HV meter is reading so incorrectly.  It seems  that 
the reading is just about half what it should be which may indicate that  you 
may have improperly converted the amp to running on 120v.  You may be  feeding 
120v into it configured for 220v hence the 50% of full voltage.   Also as Alec 
points out, perhaps the step start resistors are still engaged in  which case 
I would assume they would open up in short order or at least get very  hot, 
and you would smell something burning.  I HIGHLY RECOMMEND RUNNING  THIS AMP 
AND ALL AMPS ON 220V.  I use caps to emphasize that fact because I  do believe 
it is the best way to operate an amp.  IMHO...It seems kind of  counter 
productive to "want" to run more power and then starve the amp with half  the 
amount 
of voltage.  I suggest putting your efforts into getting a 220v  line into 
your shack instead of troubleshooting this problem.  I have  noticed as much as 
100 or more watts output from an Sb-200 running on 220v vs.  120v.  The LK-500 
would probably run more than 200 watts less on 120v vs.  220v. 
 
The step start circuit was most likely designed for  220v operation,  and 
depending on how it was designed would determine how it should be modified  for 
120v.  There are many different schemes for step starting and without  knowing 
how this one was configured, it would be hard to offer any advice on how  to 
modify it.
 
Once again, I suggest your efforts be put to getting 220v into your  shack.
 
Louie W1QJ
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