Re: {Collins} SS Rectifiers and KWS-1



 
I agree with Bill pertaining to the KWS-1 and high supply voltage problems.  
I'm running 3B28's in it and have for many years. However mine was exhibiting  
the off-frequency spur problem described in SB 4, even though, being an 11nn  
serial number, it had the fix installed at the factory.
 
The problem was solved when I installed two bucking transformers  
(externally) at the 240V supply. My line voltage had been running about 248V,  but after 
putting in two surplus T-368 filament transformers from Fair  Radio, I'm 
feeding 234V to my KWS-1 The spurious output went away and I'm  confident that the 
HV components are at least safer for a while. The  transmitter's happy for 15 
years, and so am I.
 
73 Jim W8MAQ
CCA Since 1994
 
 
In a message dated 1/27/2009 1:30:45 P.M. Eastern Standard Time,  
wcarns@xxxxxxxxxxxxx writes:

Jim,  OK.......:-), I can agree with you on the 30S-1. It is way OK with SS  
rectifiers. BUT, the KWS-1 IS NOT. I have seen it done, and many get away  
with it for a while, but The KWS-1 has some very marginally rated HV  
components including the feedthrough caps and the HV choke. These  components 
are not getting any younger and the choke particularly is  starting to suffer 
from potting compound microcracking as is the HV  transformer. Between Dennis 
Brothers and myself, we have serviced and  repaired a lot of KWS-1s and we 
both have observed that there is a much  higher failure rate observed in the 
HV areas with SS rectifiers. Between  the higher line voltages these days, 
and the aging and marginality of the  components to start with, there is a 
big issue. The 3B-28s should be used  and the choke should be lifted off 
ground if still good (Not if it has  failed to ground as a fix - big safety 
issue for next owner or you) and  the line voltage should be bucked down to 
115 V always. My "Care and  Feeding of the KWS-1" deals with some of the 
protective  methods.

Just my two cents worth, but hope it helps.

Bill Carns,  N7OTQ
K0CXX, Trustee MRCCC
Editor Signal Magazine
CCA #  94-00009
Wimberley, Texas
512 847 7010


----- Original Message  ----- 
From: "Jim Garland" <4cx250b@xxxxxxxxxx>
To:  <collins@xxxxxxxxxxxxx>
Sent: Tuesday, January 27, 2009 9:10  AM
Subject: {Collins} FW: Rectifiers


>
> Wilson, I  respectfully disagree with your conclusion. I've used solid 
>  state
> replacements in my 30S1 for years with no problems. The 30S1  power supply
> uses a choke input filter, with rather low capacitance  (I'm going by 
> memory
> now, but I believe there are two 4uF  caps in the HV supply), so surge
> current isn't excessive. Also, the  power supply is relay-switched, so
> whatever surge current is present  doesn't go through a switch.
>
> By contrast, other commercial  amplifiers, such as the 30L1 and the L4B, 
> use
> solid state  rectifiers and a capacitor input filter, with an appreciable
> surge  current going through the on-off switch. Even in those amplifiers, 
>  the
> designers didn't feel it was necessary to use a step-start  circuit. One 
> can
> argue the merits of their decision, but the  point is that solid-stating 
> the
> rectifiers in the 30S1 (and  KWS1) can be done without worry. The resulting
> voltage increase is  only about 100V, and the regulation is also improved.
>
>  73,
>
>
> Jim W8ZR
>
>> -----Original  Message-----
>> From: collins-bounces@xxxxxxxxxxxxx 
>>  [mailto:collins-bounces@xxxxxxxxxxxxx]
>> On Behalf Of Wilson  Lamb
>> Sent: Tuesday, January 27, 2009 7:42 AM
>> To: Clint  Hasty; collins
>> Subject: Re: {Collins}  Rectifiers
>>
>> Bad idea.  You have to deal with the  considerable surge current when the
>> diodes try to charge the  filter caps instantly upon turnon.  Also, your
>> voltage will  be higher, possibly overstressing some very old components.
>> Unless  you are prepared to design/buy a soft start system and investigate
>>  the voltage level, you are askung for trouble.  I've just been  evaluating
>> some PS I built in the 50s and I'm going to stay with  the 866s or 3B28s.
>> Wilson
>> ----- Original Message  -----
>> From: "Clint Hasty" <w4ch@xxxxxxxxx>
>> To:  "collins" <collins@xxxxxxxxxxxxx>
>> Sent: Monday, January 26,  2009 8:14 PM
>> Subject: {Collins}  Rectifiers
>>
>>
>> > Can anyone tell me where I  can purchase solid-state rectifiers as
>> > replacements for the  3B28's in the 30S-1. What's involved in the change
>> > out ? any  mods required after installing the solid-state rectifiers ?
>> >  Thanks
>> > W4CH
>> > Clint Hasty
>> >  _______________________________________________
>> >
>>  >
>> > SHARE THE FUN: JOIN THE COLLINS COLLECTORS ASSOCIATION  TODAY !
>> >   http://www.collinsradio.org/membership/
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>>  >  1st Wednesday AM Net 3.880 MHz-2000 local (ET, CT, MT,  PT)
>> >
>>
>>  _______________________________________________
>>
>>
>>  SHARE THE FUN: JOIN THE COLLINS COLLECTORS ASSOCIATION TODAY  !
>>   http://www.collinsradio.org/membership/
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>>  NETS: Tues & Thur: 3.805  MHz-2000 Central + Fri: 3.895 MHz-2000 Pacific
>>    SUNDAYS: 14.263 MHz-2000 UTC  +  AM Net: 29.050 MHz-1200  Central
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>
>  _______________________________________________
>
>
> SHARE  THE FUN: JOIN THE COLLINS COLLECTORS ASSOCIATION TODAY !
>   http://www.collinsradio.org/membership/
> -paypal  accepted-
>
> NETS: Tues & Thur: 3.805 MHz-2000 Central + Fri:  3.895 MHz-2000 Pacific
>  SUNDAYS: 14.263 MHz-2000 UTC   +  AM Net: 29.050 MHz-1200 Central
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_______________________________________________


SHARE THE  FUN: JOIN THE COLLINS COLLECTORS ASSOCIATION TODAY !
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