Kenwood TS-940SAT with Fluctuating Power Out
Hello. I finally was able to get logged in to this forum. I have a real brain-teaser that I'm dealing with, and I am hoping someone who reads this can help me figure it out.
I have a good ol' Kenwood TS-940SAT that is a very nice-looking specimen that has been working fine until recently (I wish I could remember the date I first noticed the problem because perhaps there would be a clue). Now, on transmit, the power output fluctuates erratically by a few watts. This wasn't really noticeable until I tried to tune up my amplifier. On the amplifier's meter those small erratic fluctuations were BIG fluctuations. That got my attention.
I spent some time going over the radio this morning so that I would have all the facts to present: on transmit, the meter needle fluctuates erratically on ALC setting, on Power setting, AND on the Ic setting. Ic is showing 7A with the meter wiggling slightly.
LATER SAME-DAY UPDATE: I got to studying on my power supply wiring job and noticed how small the wires were that I had used to connect the AC line power to the Quint power supply. And the wires that I had used from the Quint to the IOK circuit board I thought were #10 wire (which is what I had paid for). It turns out the "#10 wire" I bought was actually #12 wire with extra-thick insulation! So, it is entirely possible that I have been using wiring incapable of carrying the current the radio needs, and I just didn't notice it at first. It probably wasn't until I tuned up the amplifier that it became obvious. So, I will be re-wiring my power supply section, and will let you know if that fixes my own problem!
Tnx, and 73.
Well, I rewired that entire power supply area with heavier gauge wire, and that didn't help. THEN I remembered one day a year or so ago when I dropped something on the DC-DC unit, and smoke curled up from it. I figured at that time that the board was toast and replaced it with another one. My mistake. On a lark, I re-installed the original board, and the radio works perfectly. NO POWER FLUCTUATIONS. Lesson learned: never assume something is burned out because of a little smoke. Something apparently got a little warm, but not warm enough to destroy it.