Monday, February 20, 2017

powered up HW-100 and fixed first problem


Marc will rerun the boot attempts with the pack I wrote and with a known good booting pack, adjusting the capture and formatting rules to give me traces I can compare more successfully.


The dummy load and cable are at the local post office but with the postal holiday tomorrow, they won't arrive until Tuesday. I can't switch on the transmitter until the load is applied, but I can check out the unit under power, make initial adjustments and see how it receives signals with an inadequate short wire antenna.

I set up the power supply, joined the cable between it and the HW-100, and switched it on. Nothing. The power supply light didn't turn on at all. I pulled off the cable and tested the power switch pins on the connector that will complete the power supply primary circuit. They worked fine.

At this point, I decided to check continuity in the cable. Several pins had no connectivity at all! Bad cable. I opened the caps on the two plugs and the problem was immediately obvious. The wires had failed due to being yanked, separating several leads from the remnant down in the pins.

Wires snapped off on the power supply end of the cable
I took the opportunity to remove the phone jack cable that had been piggybacked on the connector to fit some local modification by the original owner. I removed all the wire remnants and prepared the cable ends to be soldered back in the connector. The design of the cable is very odd - no strain relief at all for the wiring on either end.

Receiver end, with spurious phone jack connected to unused pins

I soldered up the connector, checked connectivity with the meter and then attempted power up of the transceiver once again. It now powers up and I can hear hiss from the audio section when I turn the audio gain up. No antenna at all and not surprisingly, no reception.

I did the initial tests from the instruction manual, which showed that I have correct voltages delivered to the board and that all the tube filaments glow. I set the function to Calibrate, which will produce signals every 100 KHz to allow calibration of the receiver. I can hear the tones at various points on the tuning dial, but the S meter does not deflect from its zero setting.

Hooked up a short bit of wire and tuned in some CW signals on several bands. I clipped a voltmeter across the meter connections and saw that current is flowing through the meter. I then noticed that as the current increases with stronger signals, the meter pins below zero. Hmmm. Something to debug.

I will be using a scope and some reference signal to do alignment, but still lack a microphone to drive the rig. It will arrive in about a week, after I have the dummy load to let me also align and tune the transmitter.

I found some tests to do for the meter circuits, but none of them moved the S-meter upwards. This is not good, seems like I have a continuity break in the meter wires or the meter itself is defective. I did check the two resistors hooked to the meter terminals, and found they both were high. That would subject the meter to higher voltages on each post.

With the meter removed from the panel, I hooked up a resistor in series with my ohmmeter to see if the needle will deflect. Worked perfectly, thus the problem is not the meter itself. The wiring seems good but all I can check is ALC, the first of three meter settings, because the other two require a dummy load since they switch on the transmitter (Relative Power and Plate Current).

The meter is connected to an IF amplifier tube circuit in two places and will measure the relative voltage of the two lines. When I have the RF Gain all the down, the meter should be at full deflection. As I advance the RF Gain, the meter deflects downwards, which is the correct direction.

Earlier I had picked up some CW stations but that wasn't working tonight. I did swap two 6AU6 tubes, perhaps one of them is marginal. I will swap them back later. I picked up carrier that appears to be SSB transmissions on 21 meters, but the receiver is too far out of alignment to capture audio.

Lots of noise and erratic contacts, which is to be expected. More cleaning will be required. 

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