[Collins] KWS1 Problem -- No HV Comes on

[Dr. Gerald N. Johnson]

Mode switch has to be in CW, SSB, or AM, not cal or stby.

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.
>
> 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.


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.

 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.

J103 pin 7 connects to TB502 pin 12.


> 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.

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.