[Collins] KWS-1 Filter Drift

[Barockteer@aol.com]

Hello folks-

Here's the latest on my progress in restoring a KWS-1 to life. I have replaced many caps and a choke, and gotten the RF stuff to work well, and the cracked,leaky paper caps are replaced with orange drops. All things are neutralized/aligned, and I'm getting close to 600 watts out on most bands. It seems that the output is getting better as the rig is powered up for more hours - I suspect the finals were a bit gassy but the getters are working.


Latest issue is that it seems it has a typical KWS-1 problem - audio is high-frequency heavy on USB, muddy and raspy with hummy carrier on LSB. (Great 'DX' audio on 20 meters, sounds like a Heil HC-5). Extensive measurements reveal that the mechanical filter has drifted in frequency upwards by about 500 cycles. I have a sweep of the filter response for those that might be interested. The carrier oscillator crystals measure OK with my HP counter.

So, I am faced with two choices:

1. Anyone have a KNOWN GOOD KWS-1 filter for sale?

2. Get new carrier crystals cut to reposition the carrier in the correct place relative to the drifted filter passband. This sounds easy, but so far the cost of these custom crystals is pretty steep.

I wonder if anyone on the list has any words of wisdom. I know this topic has been discussed before, and that it has occured in a couple of other KWS-1's. Oh, before I forget, I have checked the caps on the filter input and output; and I've been able to get a decent carrier null on the balanced modulator.

Thanks,

Tony, K1KP