Re: {Collins} KWS-1 Output Problem - SUCCESS!

I'm back to report SUCCESS!

This is long, but I want to document it in case someone else runs into this.

First I want to thank everyone that sent me suggestions.

I had it going, then it quit, then I re-did the alignment but this time a bit differently.

My manual has some incorrect info for alignment. In the 40 meter tracking it has you aligning the 20 meter coils and caps. I knew that was wrong before and did it the way I thought it should be done.

In my google searches I found a later copy of the manual. It had the correct alignment procedure so I followed that with a couple of exceptions.

1) I used Bill Carns' method for 80 meters that he tells about in the Care and Feeding article. Made that part much easier.

2) I used W8MAQ's neutralization procedure - where you cut pin 4 off of two 6CL6s. I've used the same idea on an old Yaesu FT-101, on that it's called Cold Neutralization.

3) I used a spectrum analyzer instead of the 75A4 or a scope. My 75A4 doesn't hit all of the frequencies that the alignment calls for and I can see things that don't belong.

So after this last alignment I had full power on 3750. Great! So I started putting tools away, cleaning the bench up, ... and periodically would hit the key to make sure it was still working. Uh-oh. 40 watts again.

I checked the driver plate test point, it was about 20v lower than it was. The driver grid was also lower than it should be. Well on 80 meters, the 2nd mixer and the 3rd and 4th IF amps aren't used so that eliminates about half the IF chain. Also the XTAL oscillator.

VFO and 250KHz test points are good. Start with the tubes. 2nd IF tube. Replace, no change, put the original back. 1st IF tube. Replace and all the signals are back up! Checked the output, 700 watts again. WOOHOO! That was easy, but that 6BA6 is one of the NOS tubes I just bought.

So now it's been idling in CW for the last few hours, occasionally I go over there and hit the key and look at the wattmeter, all is well (just did it again).

So it's all buttoned up and ready to move to the radio bench tomorrow, but until I shut down for the nite I'm going to leave it running.

I strongly recommend the use of Bill's Care and Feeding info for alignment tips and test point levels for troubleshooting.

Now then, what was causing it to tune up with real low output? I don't know, exactly. But the PA Loading was a few turns beyond where it should be. So it was tuning something but I don't know what. Like I said before, when I looked at the output on the SA, I only saw the freq I was tuning.

Thanks again!
Vince - K8ZW.

On 05/08/2019 10:35 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

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?



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