KWS-1 Troubleshooting: First Analysis

One of the things I can do is trace the lines from the 4X250B final tubes (the schematic shows 4X150A), and see where their grids would get their current. It seems the 6CL6 driver tubes are one thing to keep in mind.

The green boxes are the readings I get right off the rig – and they are all good. I didn’t check anything ALC wise and don’t need to – but I am not getting any Grid Current reading an any band. So – if I had to guess where there is no voltage, I think my friend Bruce, AH0U is right,

There could be a problem on pin 3 and 11, but I am betting its pin 3. He didn’t mention pin 10 (I better test this too) – but since the KWS-1 shows good voltages or current on its meters for HV – 2100 volts, 6.3 vac Filament and 100 ma Plate Current, then that at least eliminates a few things. I am wondering about the PA Fil pin 18 and OSC Fil pins, but I’ll look at these after checking the test points with an oscilloscope on the top side of the chassis and also pins 3 and 11 on this power connector.

Howard said that it seems like the rig is not being keyed, and so who knows – it could even be a relay that isn’t working.

Looking at the test jacks – I will be especially interested in J207 – the grid current in the driver stage, but also J201 and J208 since they are the test jacks in the Driver stage.

So – it will be my first time using an RF Probe, and instead of using a VTVM, I will be using an oscilloscope. I see the person who wrote in this manual lists the 6CL6 driver tubes and shows the GRID on this jack but that is the driver grid – not the final grid.

It will be one of five things:

  1. Power Supply Voltage – something not being supplied (fuse or bad tube in the PS – or I did something wrong when I recapped it, and it would be a connection or a polarity issue on a cap or the diode)
  2. Bad tube even though they all seem to test OK. Maybe one still isn’t seated right or is somehow not making a connection
  3. I vacuumed out the area where the bottom of the final tubes because there were clumps of fiberglass insulation stopping the airflow. I was careful – but I will triple check the wiring in there
  4. A relay of some sort not making connection – W9KR had no RF Output because a dirty antenna relay contacts. I doubt mine has this issue because the RF Deck worked for Howard
  5. I did check resistors in the power supply, but in some cases because of where they were in the circuit – a few I couldn’t really test. Also – there is one capacitor I did not replace because it looked like a resistor . . .

OK – I will read the rest of the manual of the circuit description – and I also need to better understand how to use my new oscilloscope and RF Probe.

When I go through the test points, I will be on the phone with Howard, W3HM and ask that he guide me through this.

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