Yes, I had made the second mod option below on my former 30S-1 and it
worked well. I was using the original power transformer and, while it
never faltered, it did do some serious humming.
73, Joe
K2XX
Jim Garland wrote:
> I've run my 30S-1 at a higher screen voltage for years and highly recommend
> it. With the higher screen voltage, the amp easily runs 1500W output (it was
> designed for 1000W input, to be consistent with the prevailing US legal
> limit at the time). Further, it is much harder to abuse the screen current
> rating of the 4cx1000A, when its running at a higher screen voltage. I ran
> extensive before-and-after tests when I made the modification, and can
> probably find my notes if anybody is interested.
>
>
>
> There are two common ways to implement the screen voltage modification. One
> is to swap the plate transformer for a Peter Dahl replacement transformer,
> which provides about 100V higher screen voltage. (This is what I did with
> my 30S1, because the HV leads on the original xfmr were cracked and worn
> where they exited the body of the transformer.)
>
>
>
> The second, much less expensive route, is to use an ordinary 100W (or more)
> isolation transformer that sits on the accessory shelf of the 30S1 power
> supply enclosure. The primary of the transformer is wired to 120VAC and the
> secondary is in series with the plate transformer screen voltage tap. This
> is a ten minute modification.
>
>
>
> As I recall, there's also a 350V electrolytic filter capacitor in the screen
> power supply that many users swap for a 450V unit. Doing so is optional, but
> a good idea, since the original capacitor is probably somewhat iffy after
> all these years.
>
>
>
> 73,
>
> Jim W8ZR
>
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>
>
>
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