[Collins] KWS1 Problem -- No HV Comes on

[Wally Klinger]

Hi Jerry:
 I'll answer below as I take measurements and go through your instructions...> Date: Sun, 5 May 2013 20:05:41 -0500
> From: geraldj at netins.net
> To: collins at mailman.qth.net
> Subject: Re: [Collins] KWS1 Problem -- No HV Comes on
> 
> Mode switch has to be in CW, SSB, or AM, not cal or stby.DONE. It is in SSB
> 
> On April 23 I wrote to the list:
> > Tracing the circuits, I see that the plate will not turn on unless
> > two interlock switches in the power supply are closed, at least one
> > is on the front door, and one interlock switch in the PA compartment
> > is closed, which means the cover is on the PA compartment, plus the
> > emission switch has to be in CW, SSB, or AM and you have to wait for
> > the time delay relay. The standby and cal positions do not allow the
> > plate circuit relay to come on. Be sure that the lamp is good. Those
> > 120 volt few watt lamps are fairly fragile. The time delay is to
> > allow the 866 mercury vapor rectifiers to heat up. If you don't wait,
> > they will flash over and short the plate transformer and damage
> > themselves in the process. If they have been moved, especially
> > tilted, they need to have 12 to 24 hours of filament power alone to
> > vaporize any mercury from their anodes else they won't rectify and
> > will short the transformer secondary. 3B28s are a bit more tolerant
> > of voltage, but still like the time delay to get warmed up.
> >
> > Then to really get plate voltage the power connector jumpers on TB503
> > have to be correct for 120 vs 240 volts.DONE.  Checked TB503.  Set up/Verified for 240VAC.  All good.  The green filament light comes on when I turn the toggle switch on.
> >
> > Once all the interlocks and lamp are correct, then there is a slight
> > chance the plate relay can be bad, its coil is wound with fine wire
> > that can easily have corroded open. I actually pulled the wires that supply voltage to the coil on K501 during an earlier test, and measured 0 volts. What kind of resistance should I see when I put an ohmeter across the coil, and if I wanted to bring in an alternate source of AC to click the contactor on and off, what kind of voltage do I need to do this, 120 VAC I assume?
> 
> 
> On 5/5/2013 5:32 PM, Wally Klinger wrote:
> >
> >
> > Hi All:
> >
> >
> >
> > Trying to get a KWS1 back on the air.  The Plate HV will not come on.
> > No red indicator light indicating that the HV is on, nor is there any
> > buzz coming from the transformer.
> >
> > Checked all the fuses and the RF cage interlock.  All OK.
> >
> >
> > So far, I have checked continuity from Pin 3 of TB501 through the
> > interlocks, jumered the interlocks just to prove them okay, through
> > the plate switch, up to the K501 contactor. I get resistance across
> > the coil indicating that the coil is not open.  But no voltage on the
> > coil.   I swapped the time delay relay, and even jumpered over pins 5
> > and 7 to see if it is the time delay.  I have voltage on pins 2 and 7
> > of the time delay and the fan is running.  I have voltage across pins
> > 11 and 12  on TB502. I pull the wires off the K501 contactor and I
> > get no voltage. Regardless of where the emission switch is set.
> >
> The you have to trace the common side of the contactor coil, through the 
> plate switch and the two power supply interlocks to TB501 pin 3. Until 
> the contactor coil gets voltage you will find line voltage on that circuit.
> 
> My schematic shows TB501 pin3 connects to J103 pin 1.I just checked this.  I have continuity from J103 pin 1 to TB 501 pin 3
> 
>  From J103 pin 1 the circuit goes to the PA interlock switch, then to 
> the mode switch which is open on CAL and STBY, then to J103 pin 7.Checked.  good
> 
> J103 pin 7 connects to TB502 pin 12.Checked this.  I have continuity
> 
> 
> > In the RF deck I checked continuity from pin 7 on J103 all the way
> > through the RF cage interlock switch. All OK.
> >
> >
> >
> > Is there anything else that would cause the HV circuits not to come
> > on when the plate toggle switch is on and all normal conditions in
> > the transmitter are met (interlocks, cabling OK, filaments on, fuses
> > good, etc)? I appreciate any guidance that the list might have to
> > offer. 73--Wally W9BEA
> >
> Both poles of the filament switch have to make contact and the mode 
> switch has to make contact. The interconnection cable has to be good.Pulled the filament switch down, and checked it for continuity.  Both poles test good.
> 
> You could jumper TB501 pin 3 to TB502 pin 12 to see if the plate 
> contactor has comes on with the plate switch, but that takes the RF 
> section of of the safety circuit. Better just check for voltage there 
> with the doors all closed, a pain, if there's voltage the circuit in the 
> cable or the RF section is open.
> 
> Be careful with the 120 volts in that control circuit it can kill you as 
> dead as the 2 KV plate voltage if it puts your heart into fibrillation.
> 
> 73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association.
> 
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