Re: {Collins} KWS-1 Output Problem



Take a look here.  W8zr websiteThe Johnson Bearing Co.1 800 827-1048Bearings@xxxxxxxxxxxx/nWC870388x22x.406About $6 each some years agoSent from my Verizon LG Smartphone------ Original message------From: Vince Vielhaber via Collins Date: Fri, May 24, 2019 1:25 PMTo: Bill Carns;Cc: COLLINS@xxxxxxxxxxxxx;Subject:Re: {Collins} KWS-1 Output ProblemHi Bill, thanks for the response.  I do have it mostly working.  I 
followed the Care and Feeding for parts of the alignment, a newer 
version of the KWS-1 manual for most of the rest, then I neutralized it 
with W8MAQ's method.  I did have to modify the the slider.

The only issues remaining are 1) there's a problem around the 1st IF amp 
where the drive to the PA will be real low.  Any probe (scope, DVM, ...) 
touching the plate of V202 brings it back to life until it's turned off 
and cooled down again; and 2) the fan bearings.  Not sure which ones to 
order, the part number in the Care and Feeding is not found.

Thanks!
Vince.

On 05/24/2019 03:58 PM, Bill Carns wrote:
> Vince,  Have you re-neutralized the transmitter Driver and PA.   The circuit
> that Collins originally put in there was designed for the 4X150s and when
> the change came originally from 150 to 4CX250s, the neutralization was still
> functional although the tube inter-electrode capacitances were somewhat
> different.
>
> When the "improved" 4CX250B came out, the inter-electrode capacitances
> changed again and most KWS-1 neutralization networks would not get the job
> done.  The PA neutralization can be brought back "in range" by a
> non-destructive careful modification of the Plate Butterfly capacitor.
>
> This problem and the change and then alignment is described in my Care and
> Feeding of Your KWS-1 article.  This is available on our website for
> download for free in both the RX fir Your Collins Section and also a link on
> the front page.
>
> Even if you think that you neutralized it, if that slider for the
> Neutralization cap is all the way at the top, you are in trouble.
>
> I suggest you get this and read it carefully and then proceed. You should
> not run that PA without neutralizing it correctly and then checking on a
> Spectrum analyzer all across all bands.
>
> Good Luck.
>
> Bill
>
> Bill Carns, N7OTQ (Trustee K0CXX)
> Current CCA Board of Directors
> Past President, Collins Collectors Association
> Founding Board, Collins Radio Heritage Group
> Editor, Signal Magazine (Retired)
> Wimberley, TX
> 512 618 2762  (Cell)
> 512 847 7010  (Home)
>
>
>
> -----Original Message-----
> From: Collins [mailto:collins-bounces+wcarns=austin.rr.com@xxxxxxxxxxxxx] On
> Behalf Of Vince Vielhaber via Collins
> Sent: Wednesday, May 08, 2019 9:35 PM
> To: Collins 
> Subject: {Collins} KWS-1 Output Problem
>
>
> 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.
>

-- 
   K8ZW  http://www.metalworkingfun.com   http://www.hamradio.fun
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