Kenwood TS-450S/AT

HF Transceiver

1991 saw Kenwood's successor to the TS-440 by an order of magnitude.  That's what some say while others believe the 440 was poopoo'd for simply having a bad component that Kenwood knew should have been fixed by the time it went into production.  Still, the TS-450S and its 6 meter capable brother, the TS-690S, became widely accepted as one of Kenwood's crown achievements at that time for the price point.  

My unit is a 1991 early release and has finally suffered a couple of issues.  The first, the infamous audio amplifier electrolytic capacitor, C104 failure.  Oddly it was an Elna branded cap while none of the other held a brand name.  Likely this one wasn't available from Kenwood's supplier or an engineering change prior to production saw early issues with the capacitor originally spec'd out.  This is speculation though.  So many haven't failed but many have.  I wonder how many were "trashed" because of the audio going out or was determined unrepairable.  I would have liked to have my pick of those units for pennies on the dollar.

The second issue is an overly sensitive ALC.  Either it's mis-calibrated or there's a problem with the MIC circuit causing it to be overdriven.  I have had reports on several occasions my audio was low when the ALC was just beginning to activate.  I've also gotten a couple of emails saying I was wide of my 3kHz when I had the MIC gain turned up to where the receiving station could hear me but the ALC was full scale and beyond.  So I basically stopped using the rig for transmitting but kept it as a receiver.

That's when the audio issue cropped up.  I started hearing "static" intermittently at first then more and more often until it was a constant "frying of bacon" sound even with the volume turned down all the way.  I shut the rig off and put it on the repair queue shelf for later.

October 10, 2022

I got the rig out and removed the main top and bottom covers.  After removing the IF board to repair the audio section I inspected the rest of it for any signs of leaking caps.  So far, none.  Even with a black light.  It was worth a shot to see if dried electrolyte fluoresces or not.  No other abnormalities were visible under a magnifying glass so I was confident the audio section was repaired.

The board went back into the radio and tested.  No frying bacon after 30 minutes and I was satisfied.  Next up was the ALC issue.

I found a copy of the service manual online and began to peruse its contents.  Interesting stuff if you're into electronics.  However, it's short on wording since it was written for trained personnel.  I had to figure out what the service procedure meant.  After learning some of the abbreviations I figured out the rest.  I cannot do a full procedural alignment as I don't have a spectrum analyzer.  Without that there are several things that are affected downstream from that point that may be off.

Undeterred I decided to try out the Adjustment Setting after getting the oscilloscope, frequency counter, 10megohm impedance multimeter, and signal generator warmed up.  It's weird to hold down three buttons with two hands then press the power switch without the thing scooting across the table.  Good thing I have a silicone mat!

The first thing I was able to check was the ALC voltage.  It's supposed to be 3.0V +- .03V.  My DMM read 2.963V  Just inside the .03 allowance.  I rotated the VR full sweep and back until I got 3.001V.  I don't have the steadiest hands and being unable to rest my wrist with the probe in hand made it sketchy.

It doesn't seem like a lot was accomplished tonight but I'm getting used to reading the manual's format shown below. 

As I get more comfortable with the format and how to interpret it, it will get easier to do the tasks.  Sometimes the Method column doesn't make any sense.  Sometimes the Condition column confuses.  In the end I have to keep in mind this is for a Kenwood trained tech and they would have done several of these in a week.  Kenwood no longer supports nor will repair anything older than the TS-590SG on up to the 990.  Not even the TS-2000 was supported as far as a Kenwood rep told me.  Though I do like the 2000, I think I'd prefer the TS-830S with the tube finals though the TS-950 wouldn't be half bad.  I've had Icom and still have my Dad's IC-745 waiting to get looked at and I have an IC-7100 mounted in my Jeep XJ with an AH4 tuner for the whip.  But I think once this 450S goes it'll make a nice nightlight on the shelf.

That's it for tonight!

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October 12, 2022

Well, I did it.  I hit the write button on the wrong memory slot while in the microprocessor's adjustment mode.  The ALC has four voltages.  2.5 reference, the start voltage, the ZONE voltage, and the Full Scale voltage.  I saved the start voltage into the ZONE voltage slot and the radio won't modulate.  I thought it odd the meter didn't show anything and rather than hitting the button to go back one step, I hit the write button which saved the setting into the EEPROM and is now part of the RESET parameters.  I don't have a function generator so I bought one.  It should be here, according to Banggood, November 27th.  Great.  Fun.  Yippee.  Dammit!  If you want something fast from Banggood, call them and make sure the item really is where they say it is.  Mine said from Canada but actually is coming through Canada from China instead of going direct to L.A. then to me.  So I started working on the Heathkit HM-102 RF Power Meter in the meantime.  Check out that blog from the main page.

By for now.

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November 2, 2022

I am unable to correct the write error into the EEPROM to get the ALC configured correctly.  The first setting is to establish the first lighted dot on the display's meter.  It goes straight to Zone Max.  I have tried to get it to set below that with barely any signal (1kHz@5mV) into the MIC connector on the front as the procedure requires.  I have attempted to use the microphone and the same tone with worse results.  I believe the setting cannot be remedied at this point.  If purchasing a replacmeent, good, used digital unit board I might have a better result since it may still have its original ALC configuration stored.  Not that I'd be able to extract it and put it into mine but at least it would modulate again.

It may be age messing with the IF Unit board and all the electrolytic capacitors require replacement.  It may the EEPROM will not allow writes to it any longer.  Who knows.  At this point my first HF rig I purchased after passing my General Class license at the Huntsville Hamfest in 2013 makes a good short-wave receiver at the very least.  Until I get my Heathkit SB-301 and SB-303 receivers going, this and the Hallicrafters S-120 receivers are all I have to hear what's going on in the world on radio.  And so it becomes.

Project closed.

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