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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