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Kenwood TS-430S; tried to scan, burning smell; no reception, one digit on display

JohnS

New Member
Sep 19, 2022
2
0
1
61
I bought a used Kenwood TS-430S transceiver last year. I put a CW filter in it, and I've used it mostly for searching for CW signals and then for CW QSOs. I had a single SSB QSO months ago, with no problems at that time. I've also successfully done some FT8.

I have never scanned with this radio. and I have had good luck with it up until about two weeks ago, when I finally decided to try out its ability to scan a range of 20m frequencies. I looked in the manual for what panel buttons to select, and when I began selecting scanning options, I smelled something burning, and now the radio is unusable. The frequency display and reception last only for a few seconds after powering the radio on, only a single digit appears on the screen, and there is no reception. The single digit doesn't change when the tuning knob is turned, so it appears not to be part of the frequency. It is mostly either a 6 or a 7.

I cannot remember exactly the sequence of buttons I pressed.

I took the top cover off and went over it with a magnifier, but I saw nothing wrong.

It was suggested to me that "a regulator or the 12v to it has failed".

This is my first post and I am hoping for some suggestions and for some good reading meanwhile!

Thank you,

JohnS
 

nomadradio

Analog Retentive
Apr 3, 2005
5,557
8,175
573
Louisville, KY
www.nomadradio.com
That radio has a variety of step-down voltage regulators inside. More to the point it has numerous aluminum electrolytic capacitors. All of them have reached that "awkward age" over 30 years old. Only takes one of them shorted internally to do something like this. Normal procedure is to "take inventory" of all the internally-regulated voltage sources. Doing this with a 'scope can reveal faults that a meter alone won't. A capacitor that fails as an open circuit can cause a voltage regulator to become an oscillator. A 'scope probe on that regulator's output reveals this at a glance. A meter will only show a somewhat-lower than normal reading as a rule.

When a radio loses that much functionality all at once, the culprit usually lies in a power-supply function.

73
 

JohnS

New Member
Sep 19, 2022
2
0
1
61
That radio has a variety of step-down voltage regulators inside. More to the point it has numerous aluminum electrolytic capacitors. All of them have reached that "awkward age" over 30 years old. Only takes one of them shorted internally to do something like this. Normal procedure is to "take inventory" of all the internally-regulated voltage sources. Doing this with a 'scope can reveal faults that a meter alone won't. A capacitor that fails as an open circuit can cause a voltage regulator to become an oscillator. A 'scope probe on that regulator's output reveals this at a glance. A meter will only show a somewhat-lower than normal reading as a rule.

When a radio loses that much functionality all at once, the culprit usually lies in a power-supply function.

73
Thank you, nomadradio!
 

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