A crowded work bench

Just when I found time to restore the Yaesu FR-101, this baby came in. I got this rig for free from PA0TBS, who found out that I like to restore old transceivers.  It’s an old Kenwood TS-515, with power supply/speaker, second VFO and optional filters installed. Cosmetically it’s in a reasonably good shape, apart from some fading letters on the front panel.

No SMD and integrated circuits to worry about

Partly cleaned switch

The same cannot be said of the inside, unfortunately. Moisture made a mess of switches and pots. The band selector contacts were completely covered in copper oxide, which made it impossible to select anything. As a result, testing both receiver and transmitter was impossible. There are some tricks to fix that. Glad I have a background in chemistry! I removed most (but not all) of the oxide, and now the selector works like a charm. Next week I will remove the remaining traces of copper oxide, after which I will look into the transmitter section. I don’t expect to encounter many TX problems though, if any.

Only one mysterious defect will have my attention for sure: as soon as I switch on the rig, the meter jumps to the middle of the scale and stays there, regardless of the mode of the meter switch. Can’t be a big problem, but I will have to study the schematics for clues.

If the transmitter works OK too, the rig will shipped to its new owner, PD0DR. He will take care of the cosmetic aspects of the restoration. I suck at that anyway.


2 comments on “A crowded work bench

  1. Hi Bob,

    I use Tartaric Acid. It’s a so-called ‘weak’ acid, not aggressive/dangerous like sulphuric acid, but just strong enough to dissolve copper oxide. The same stuff is often used for scale removal in drip coffee machines. Before applying any chemicals, I use special paper (high grade kitchen paper equivalent) to prevent the acid from leaking onto the circuit boards. The switches are wrapped in the stuff before I slowly, drop by drop, apply the acid onto the oxide. An old toothbrush can speed up the process.

    Keep an eye on the progress, repeat the process if necessary, and rinse the contacts afterwards in the following order: 1) distilled water, 2) alcohol. Let the switch dry for a while, then spray some WD-40 on the contacts. Wait an hour or so, and turn the switch around a few times.

    I did this quite a few times already. If you never did this before, you might want to practice on something less valuable first.

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