Fred’s TS-440s Repair Adventure Part 1

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Working on KG5WNN, Fred’s TS-440S.

It was reported to have no power output, and off-frequency/warbling signals.
It had been working fine years ago, but after being in storage for years, and now it’s not happy.

What I’ve found:
1.  Power output starts off dead but after a few minutes warm up, power levels creep up to 100+W starting from low bands (160/80/40) initially, then upper bands (20/15/10)
2.  Receive signals are drifty and there are unlock artifacts every few seconds
3.  The display showed Phase Lock Loop unlock once (when unlocked, the display shows a series of “dots”)
4.  The VCO5 lock test point was wildly varying from 4.5v to 6.8v.  I think it should be a stable DC level.
What I’m working on now:
The older Kenwood TS-4XX and TS-9XX series had very well known problems with the glue used in the Variable Control Oscillator section of their boards.
This was known as Sony Bond glue, used to secure components to prevent microphonics due to vibrations, like when operating mobile.  This stuff was widely used in many audiophile radios, too.  Unfortunately, over time it becomes conductive which causes havoc to sensitive electronics (like a VCO).  It is by nature, hydroscopic, or prone to absorb moisture.  Of course, moisture catalyzes oxidation and corrosion as well, so you get the picture of why its so infamous.
Current effort:  Remove the glue from VCO 5, cleanup board and components, resolder, and see which problems go away.  More to come.
73
-dave
W5OC

5 thoughts on “Fred’s TS-440s Repair Adventure Part 1”

  1. My TS-450 is having problems with failing electrolytics. There’s one notorious one in the audio chain. It sits over a trace to the 455 kHz filter; the released electrolyte shorts that filter and creates noise. Cleaning the board and replacing that capacitor helped enormously. I’ll send details if you want. I don’t know how similar the boards are.

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  2. I had the same issue with my ts-440,, once I removed the glue it worked but wasn’t stable, I then found an intermitting very small coil, if I moved the coil the legs would read like10 ohms then infinity, I ended up buying a new board on ebay, that was said to be working then found that board had the glue issue, Out of the two boards I made one good one. Radio has been fine every since.

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