Re: {Collins} KWS-1 Output Problem



My first thought is that the Cap or inductor has slipped out of alignment. When the shaft of the Air caps or inductor get tough to turn, they can slip and come out of alignment. I would check the alignment and make sure you are tuning the PA correctly.

My second thought would be one that caused me many, many hours of pure frustration.  The HV feed through cap on the back of the transmitter. This an oil filled feed through cap where the B plus enters the chassis. Mine was leaking current and leaking Oil.  It would load up with very low output power and then sometimes it would short and cause full current and blow the Fuse.  I would for sure replace this cap either way. I used HV wire with a drinking straw over the wire to pass the HV in and then used a 5KV disk cap for bypass. It has been working great at 800 watts out on SSB ever since. I used it the last few nights on 75 meters.

C

On 5/8/2019 7:35 PM, Vince Vielhaber via Collins wrote:

Back around '77 I bought my Golddust Twins w/ accessories from the original owner.  Included were the original 4X150 finals.  He did all the updates to both the transmitter and receiver as they came out.

Sometime after I got it the 4X250s went out and when I replaced them with 2 new 4CX250Bs I had problems getting any output - even after alignment.  So I put the 4X150s in and it had worked fine. I figured there was either something wrong with the tubes or CX weren't compatible.

The 4X150s worked fine for a number of years.  At some point, I my antenna came down (long story, babysitter, kite, ...) and I never got it back on the air.

Fast forward to now.  25-30 years went by and I didn't run the transmitter and only sparsely used the receiver.  Needless to say many caps had dried out in both.

Got the receiver working good now but the transmitter is giving me some grief.

After the power supply rebuild I have the all the supply voltages working right, loaded it up (with the 4X150s) and got around 700 watts on 80 meters  (CW).

Not wanting to keep the 150s in there, I put a fresh set of NOS 4CX250Bs in it.  At the time I had forgotten why the 150s were in it until after I went thru the alignment. I used the W8MAQ neutralizing method and when I was done with the alignment I loaded it up on 15 meters.

Loaded up nicely to 500ma, I looked at the wattmeter and it says 40 watts.  Huh?   Tried a different wattmeter, also 40 watts. Tuned up on 80 meters, once again 500ma and once again 40 watts out (CW).

Supply voltages are good except the TUNE voltage is low.

I looked at the output of the transmitter on a spectrum analyzer and all it shows is the one signal.

I bypassed the TR relay, no difference.  Yes, I'm using a dummy load.

What am I missing?

Thanks!
Vince.

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