[Amps] LK 550-ZC

[Rob Atkinson]

I'd say you did an adequate test assuming you got three tubes to show
orange anodes for at least 10 minutes.  I had thought the reason for
the high fan speed (and resulting noise) was that there are three
3-500s in that amp _but_ they are not cooled in chimneys with air
coming up from the bottom.  I am okay with a pair being cooled from
the side, but a third tube (with them in a triangle) means to me that
one tube gets less air exposure, so they need to be blasted even more.
  Maybe the cooling fan line-up varied over the versions of that
model--I have only seen interior shots of one.

Rob
K5UJ

On Sat, Mar 17, 2012 at 1:13 PM, Dick Green WC1M <wc1m73 at gmail.com> wrote:
> I use mostly CW, with varying lengths of transmission. But there's a big
> difference between the modes I use for operating and what I did to test the
> tube temperature before and after the mod. I transmitted continuous CW; I
> went key down, continuous RF for as long as I could at full power; I reduced
> power and transmitted even longer, as I would if I was doing a typical RTTY
> QSO, and repeated the sequence for several minutes. I also measured the tube
> temperature while operating in CW contests. I did my best to simulate the
> toughest conditions I expected the amp to endure, driven not just by me but
> by subsequent owners, without exceeding the tube ratings.
>
> I wouldn't be surprised if my testing was more rigorous and my measurement
> equipment was more accurate than what Denny used when he designed the amp.
> No way I wanted to replace three 3-500Zs or any other components in the amp.
>
> 73, Dick WC1M