[Collins] KWS-1 Update (a bit long)

[Barockteer@aol.com]

Seeing as so many folks posted helpful suggestions in response to my question about soft finals in my KWS-1, I thought I'd post a progress report.

1. Thanks to the many folks who suggested checking the PA tank circuit tracking. I had already done this correctly according to the manuals and the K0BS video.

2. Jerry suggested I needed more PA grid drive. This sent me off checking the various stages ahead of the PA. I chose to just get a single band working right at first. I found a bad cap in the 15 meter mixer tank, which meant that the 15 meter tank wouldn't track. The cap, a silver mica, was low in value. The tipoff was that the trimmer cap was at max/min (no 'double peak'). I replaced the fixed cap and the gain on 15 came way up.

3. Next I looked at the driver tank. I had trouble neutralizing the PA plate-driver tank (gimmick cap all the way to the top of the slot). This sent me checking the feedthru cap, which is at the bottom end of the driver tank and forms the divider for neutralization. I found that this cap was also way low, down to half the spec'd value. I padded it back up with a dipped silver mica, and voila! 

4. I was now able to get a good neutralization of the PA. This was folllowed by much more correct behavior, including being able to get PA grid current, and the PA tune dip corresponding with max power out. Max power is still down, only 400 watts out, so I still suspect the finals are 'soft'. I'm assuming that if you can drive them into grid current when properly loaded, that's all she wrote as far as power out.

Thanks for the help; I'll post further updates. 80 and 40 meter driver outputs are still low and distorted...

73,

Tony, K1KP