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I have violated the Rule of Three!

I have violated the Rule of Three (many times over on this subject) as this might be posting #9 about the HW-32A.

At times you do something that is absolutely wrong, but you seem to get the right result. I have suspected for some time that there is an issue with the ALC circuit that is preventing the HW-32A from reaching full output. This posting is to highlight such an event.

The ALC circuitry in any transmitter essentially puts a brake on the input to prevent flat topping or overdriving the final. The flat topping or overdriving results in an awful signal and sounds like a buzz saw and affects transmissions close to your signal. It is not only bad form, but simply a bad signal.

The ALC can take several forms but in general the input to the final amp stage is sampled and if it exceeds a certain level generates a negative voltage applied to the circuit in this case to earlier stages to reduce the gain. It is a loop and hopefully a fast time constant so that the output sounds excellent and of a more or less constant level. It is in essence similar to Receiver AGC.



To the Grid (Pin 2) of the 12BY7 are two resistors, a 47 Ohm (R50) connected at the other end to Pin 4 of L2 the Driver Grid Transformer. Also connected to Pin 2, on the 12BY7 is a 6.8K Resistor (R51). To the other end of the 6.8K we have a .02Ufd bypass cap, a connection to Pin 3 of L2 and finally a connection to a 47K resistor connected to the ALC Buss. 

Looking closely at R50 and R51, they are essentially in series across L2 with most of the secondary voltage appearing at the Grid of the 12BY7. The series combo is a voltage divider! I disconnected R51 from the circuit (the wrong part) and we have Pin 3 on L2 at AC ground through the .02 cap and a 47 Ohm resistance from Pin 4 to Pin2 on the 12BY7. ALC is still provided through the 47K through the L2 winding and on to the Grid through the 47 Ohm resistance. Close to 80 watts out on tune but regrettably unstable. 

So, there is something awry in the application of ALC. A better test would be to remove the 47K which disconnects the ALC to the 12BY7, but then we risk flat topping and a bad signal.

I have settled on a compromise approach where the tune level is set at 10 watts and on SSB I get 40 watts PEP to the antenna. I have set the bias level up at tad bit since I have 300 VDC on the plates/screens. The 40 watts may also be the finals are not 100%. 

So, let's see if I can make some contacts at 40 watts and I did! Sometimes luck prevails and last night I had a nice coast to coast contact at 2015 PDST with KC1CWW, Herb, in Boston running 40 watts to my Delta Loop. So that indeed was a pleasant surprise after almost two months of work. There still is an issue because I can't hit 100 watts, but at this point I am tapped out. I now will turn my attention to building the JF3HZB package for installation in the HW-32A and noodle a bit more about the why of only 40 watts.

Them that know can make it go.

Everyone comfortable that old what's his name may be dragging us into a War in the Mideast. The hawks in his orbit must be sharpening their knives. A war however shifts the focus off of the economy which awaits the boom that was promised.

Perhaps by drafting up a big army and sending them off to war is a solution to the homeless and immigrant problems. Just wonder how many of those hawk advisors actually saw military service in a hot war zone. Trust me if you have served in one of those zones, your perspective is much different, and I do know. 

73's
Pete N6QW

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