Kenwood TS-830S - Bandswitches

A customer came to us with this Kenwood TS-830S right out of the 1980's.  This hybrid radio isn't something we see everyday.  It is clean and well cared for, however the band switch failed to select the 40 meter band with any reliability.

There are lots of notes on how to do this, so I won't go into a lot of detail since someone else has documented this procedure very well.  https://www.k4eaa.com/bandswitch.html

• Pull the final tube nearest the center of the radio, and the driver tube.
• turn the bandswitch to 160m and loosen the setscrew
• turn the bandswitch to 30m and loosen the setscrew
• pull the shaft straight out
• unsolder the 3 wires, and disconnect all connectors
• undo the mounting screw and pull the board out.

Suffice it to say that the band switch contacts were not well attached electrically to the board traces.  Many were corroded, or had loose rivets.  I saw suggestions on how to attach them with conductive paste.  This didn't seem like a good solution, when solder is king!  One contact was pretty badly twisted, so that had to be addressed with some fine mechanical adjustment to get it just right.

A fine diamond-tipped engraver was used to clean the corrosion from each contact, rivet, and trace.  It was then easy to flux and solder the contacts directly to the board trace.  I fixed EACH and EVERY contact in ALL the bandswitches, not just one.  They would all eventually all succumb to failure if left alone.  Each switch contact slider was treated with De-Oxit and checked for continuity.  This fix will outlast the rest of the radio.  The plastic parts have already begun to crack.

The RF board wasn't too hard to take out, but there were three wires that had to be unsoldered.  One was hidden under the board.  (Thanks a lot Kenwood!)

All back together and right on frequency.

IC-28A Volume and Squelch

My first 2m mobile rig was the IC-28A.  With a healthy 25w output on high and a 5w output on low, it is compact and a good little radio.  I gave $20 at a hamfest and I still use it as my go-kit radio for events and the XYL's car.

The volume and squelch controls were getting pretty scratchy.  The volume finally gave up and wouldn't make contact with the wiper, which meant full volume!

Consulting the manual showed that Mouser had the parts in stock

Mouser #:	688-RK097111202P
Mfr. #:	RK097111202P
Desc.:	Potentiometers Potentiometers Flat 25mm 10k

Mouser #:	688-RK0971114D0B
Mfr. #:	RK0971114D0B
Desc.:	Potentiometers Potentiometers Flat 15mm 10k

What was not apparent at first was that the pin arrangement spacing on the volume control was not exactly the same.  This required some modification to the sub board.  A #61 drill bit in a manual push drill made short work of this small modification.  The potentiometer tabs were easily bent over to make contact with the original pads.

The other difference that had to be dealt with was the difference in the shafts.  The original was a splined shaft, these new pots have a D shaft.  Adapting the original knobs was reasonably easy.  Since they are plastic and have a bit of elasticity, they were drilled out with an interference fit.  They could then be pressed on the D shaft and still stay in place.

The next project for this radio will be to build a Lithium battery pack for it and make it so it can be mounted to my bicycle.

Surface Mount repair - Lead Cut Method

The subject this morning is a USB to CAT CI-V interface cable.  Someone (not me) plugged it into the wrong 3.5mm port and blew the chip up so badly that the case was deformed due to the heat.  The chip was obviously bad, there are very few other chips on the board, so I just ordered a new chip.

Some folks don't have a hot-air desoldering tool for surface mount components.  So how does your average Plugger of ham get a multi-pin surface mount chip off the board without damaging the board?  When you know you have a ready replacement chip there's an easy way to remove it from the board.  Don't try to unsolder every lead and try to preserve the chip.  You will get frustrated.  Just clip the leads off with your best fine clipping tool or EXACTO knife.  Tip the chip up and clip the remaining leads.

I have a simple general use soldering iron as well, it gets a LOT of use.  I don't file my tip down.  I take it out anneal it in a and hammer it down to a fine point on the anvil.  The act of hammering it to a point makes the tip hard again.  I find it lasts a lot longer this way.  You will need a sharp tip on your iron to do this properly.

This is what makes it easy, just take the hot soldering tip and wipe it across the lands of the board.  The clipped off leads will stick to the iron and they will just be left behind when you dip the iron's tip in the cleaning sponge.  Easy!

Once the chip is off then using a set of helping hands and magnifying glass, putting the new chip in place is simple (provided your hands are steady and your eyesight is good).  The lands should be clean and only a tiny amount of solder is required to make the connection.

None of us are getting any younger, so using a eye loop and a magnifying glass in conjunction can be helpful too.  Hope you find these tech tips helpful.  de N3FIX at the Cly Institute for Radio Repair.