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Kenwood TS-940SAT with Fluctuating Power Out  

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Francis
(@francis)
Active Member

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.

Francis WA4ZYN

 

 

 

 

 

Quote
Posted : 02/06/2020 2:06 am
Francis
(@francis)
Active Member

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.  

 

73,

Francis WA4ZYN

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Posted : 18/07/2020 11:20 pm
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