Simple tune up for the KWS-1 The KWS-1 Service Bulletin SB-6C is to correct oscillation on 80 Meters when used with a high reactance antenna in early models of the KWS-1. In SB-6C the caps C-714 & C-402 are replaced so thanks to John Kennedy W5DJ and Bill Carns N7OTQ, here is a simple way to make the mod and then tune the transmitter.

Instead of replacing C-714 & C-402 you add a 1000 pf discap shunted across C-714 and one 5 pf across C-402 this will achieve the same results and is a lot easier to get at. The next step is to do an alignment of the transmitter, however there are a few tricks to it and if this is your first time there are a few black holes to watch out for. Lets start with equipment needed. Stable signal generator with a range of at least 3.000 to 4.000 Mhz. 30 Mhz RF oscilloscope. insulated alignment tools. RF Volt meter (HP-410C) Optional. Spectrum Analyzer (If you have one).

Step #1 will be to check the band crystals, follow the instructions under section 5.2.3.3 CRYSTAL OSCILLATOR ADJUSTMENT. Step 2 will be to make sure all tubes are good then check the traps, on page 5-9 of the manual under 5.2.3.4 Trap Adjustment it clearly states to DIP or tune for MINIMUM signal on the receiver S meter follow these steps vary carefully. The caps are accessible thru small holes in the bottom of the KWS-1 exciter.

In this step we do not want any of the other oscillators running to confuse the alignment so remove V104 (12AT7) and RT101 (3FT4A) this is the ballast for the PTO tube. Connect the scope to the 6CL6 Plate (BNC Connector) near the back of the chassis, and connect the signal generator to the 250 Kc injector near the front of the chassis. Set the main tuning dial on the KWS-1 to 3.1 and set the signal generator to 3.1 and the emission switch to CAL slowly increase the signal until you see a waveform on the scope and some indication on the PA GRID meter on the front panel. Tune L201, L206, L203, L204, L207 & L701 for a peak on the scope. Change the KWS-1 tuning dial to 3.9 and the signal generator to 3.9 and peak all caps marked 3.9 (located near the coils you just adjusted).

Repeat these steps until no more gain can be achieved by adjusting the 3.1 coils and 3.9 caps. This adjustment is very important as ALL other alignment is based on the 80-meter alignment being correct. Replace V104 & RT101 and remove the signal generator and set the emission switch to "CAL" and increase the "Carrier Level" until you have some indication on the "PA GRID" meter.

Next run the KWS-1 main tuning dial from one end of the band to the other and verify the signal on the scope (Still connected to 6CL6 Plate) remains clean and even, the only difference you should see is the waveform getting longer and shorter as you move up and down the band and you may see the waveform increase and decrease but right now we are looking for distortion (Use the Spectrum Analyzer if you have one). If this check's out then move on to the other bands. you can follow the procedures in the manual for the other bands now using the correctly aligned PTO oscillator as the signal source and monitoring the scope and receiver as outlined in the manual. If you have any questions send me an e-mail and I will try to help you further.