Re: {Collins} KWS-1 CW Keying Circuit - HELP !!



Thanks Bill, it is serial 1225 so I think it may have been added.  I don't
know if I told you but this was Chuck Ripple's KWS-1 and he told me he did
all the updates and the preventative fixes you mentioned in your care and
feeding article back in 2006.  So I guess I will have to put the radio onto
its side and take off the bottom panel and dig into this further.  Can I try
to tune her up first and see if any other issues or should I fix the key
issue first ?

By the way can I use any small 2 mH choke or do I have to worry about
current handling?

73 Jerry
K1JOS

-----Original Message-----
From: Bill Carns [mailto:wcarns@xxxxxxxxxxxxx] 
Sent: Tuesday, December 18, 2012 1:55 PM
To: 'Jerry'; collins@xxxxxxxxxxxxx
Subject: RE: {Collins} KWS-1 CW Keying Circuit - HELP !!

You are correct about the location of the input line filtering components.
If your unit is past the production change, and or has the SB change
installed, there is a clamp diode associated with that line that was put
there in production or added later with a SB..  This is a clamp diode for
the key line to take the inductive kick back voltage off the relay contacts.


I suspect that this diode has checked out (it was originally an older style
cube selenium rectifier) or it was installed improperly during the SB
update. It then could have taken out the little choke in the line filter. As
installed by the factory, that clamp diode was added back in the same area
as the filter components. If put in by the owner, it could be back there or
around the relay. I have also seen some folks add a 1N4007 or the like right
at the relay contacts - check there also.

You are on the right track...  Keep going.


Bill Carns, N7OTQ
K0CXX, Trustee MRCCC
President Collins Collectors Association Editor, Signal Magazine Founding
Member # AC94-0009
512 618 2762 (Cell + VM)
512 847 7010 (Home + Fax)




-----Original Message-----
From: Collins [mailto:collins-bounces@xxxxxxxxxxxxx] On Behalf Of Jerry
Sent: Tuesday, December 18, 2012 12:04 PM
To: collins@xxxxxxxxxxxxx
Subject: {Collins} KWS-1 CW Keying Circuit - HELP !!

Hello Listmates,
 
I hope you can offer some suggestions where to go next with this problem:
The J102 CW key pin 3 is not keying the radio when grounded to J102 pin 13.

 
Checking the schematic the CW Key line is in parallel to the Test-Key knob
and I can key the radio with this knob switch so I feel pretty comfortable
believingthe problem is not in the keying network or associated
wiring/switching in S101A or C.   At first I thought it was an open line or
problem with the J102 connector itself, however I confirmed with a DVM that
J102:13 is connected to ground BUT I also found that the resistance between
J102:3 to ground was only 38 ohms with the Test Key knob open or closed!
Each pin on J102 has an LC filter and for J102:3 on the schematic it is a
feedthru 1000 pf cap (C337) and a 2mH choke (L255).  I thought the
feedthrough cap must be leaking straight to ground and I am measuring the
resistance of the choke but if that was the case the radio would always be
in a keyed state.  I cannot find the location of these LC filter for J102 in
any of the manual figures but I guess it must be out the bottom of the RF
deck right near the J102 connector.  Before I go on a wild goose chase (and
disassemble the RF deck) does anyone have any other ideas or suggestions as
to what could be wrong?  Could someone take a look at the schematic (see
1958 edition  on CCA website as this is the first one that shows the Test
Key knob circuitry).
 
73 Jerry
K1JOS
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