Fifty year-old Sanyo transistor radio still works perfectly - should I be surprised?

That's life.

I have Sony pocket radios that are 45 years old that work properly. It's not _that_ unusual.

Probably bad caps.

If the radio only plays oldies and 1950's rock-n-roll, you have a problem.

Dry joints? I've never had to lubricate my solder connections.

In order of frequency:

- Leaky batteries and corrosion damage.

- Grease on moving parts (tuning capacitor, volume pot, on-off switch) has dried out.

- Bad electrolytic caps

- Loudspeaker coil rubbing on magnet. Warped cone.

- Carbon comp resistors changing value.

- Difficulty finding schematics and docs.

- Package leakage on the old round cylindrical xsistor packages.

- Tiny xformer wires corrode.

- Crumbling plastic parts, rotting fake leather, peeling chrome plating, peeling labels, and faded decals.

- Rubber embitterment, especially the power cord.

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I have a 'Good Companion' 6 transistor radio built from a kit supplied by Home Radio of Mitcham (south London) which still works fine. Bought in '62 with my first weeks pay...

It uses a PP9 battery which gives several months of heavy use - compare that to modern designs. ;-)

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    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Oh I dunno. Better than a lot of modern stuff.

It's what describes a failed solder joint as well as anything - they can look sort of dried out.

That can kill a new one too.

Can't see dried out grease on a tuning capacitor stopping it working.

Same with that.

They're usually so simple and basic you can wing it. And older stuff didn't tend to have maker's special part numbers on components.

Not seen that one. Aren't they glass encapsulated?

Again, most of these are cosmetic. Will still work, though.

PVC insulation was pretty common 50 years ago on hook up wire.

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    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Tin whiskers/ metalisation (Ag/Al ?) creep on the dies of transistors, certainly on Ge quite common but I suppose we must expect to see more of it on old Si transistors as well, having had decades now to develop.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

That is called a 'cold solder joint' in the US, because it is typically caused by too low of a soldering temperature to make a good joint.

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Don't you talk about 'wetting' when solder flows? Turns from a solid to a liquid? But whatever - either description works for me.

FWIW I'm not sure all failed joints are caused by too low a temp - you see them on factory soldered boards too. Famously like round a LOPT - where the vibration and heat causes the problem.

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    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

not

yeah. but caps in transistor radios of that age lived an easy life compared to those in tube radios, so maybe could survive longer.

i bet the solder joints in that thing were absolute perfection.

random old fart digression: for a while in college i worked at the sony warranty repair place. we had an old sony table radio which had survived a fire; melted into a random mass with a couple of knobs pointed in random directions; of course, still worked fine.

Wetting is when the liquid solder flows completely over the oxide free surface. It is one step of the soldering process, and the hardest to control in automated soldering. A profile has to be created, and carefully followed for constant quality. Air temperature, humidity and barometric pressure changes can cause problems, as well as moisture that has ben adsorbed into the blank PC board and components. Any of these can cause cool spots, and in extreme cases cause the PC board to delaminate as the moisture is boiled away.

Solder passes from a liquid to a solid state, not a dry state. Some alloys also pass through a plastic state that allows movement as it cools into the solid state. Any movement during the plastic state is what gives the dull gray, rough surface of a cold solder joint. Use of eutectic solder, which has a very narrow temperature range with a plastic state, it reduces cold solder joints. 63/37 was the preferred alloy, before the EU screwed the pooch with their ROHS bullshit.

As far as bad solder on heavy pins, it takes more to bring them to the proper soldering temperature, and causes more problems. You can wave solder everything else perfectly, and not get the pins on a transformer anywhere near hot enough for proper wetting. Since it takes longer to bring them to the proper temperature, the pins need to be as clean and oxide free as possible.

I was involved in improving our reflow process when the company moved to higher pin count surface mount ICs. We had a horrible initial failure rate when we added the newer devices to our process. We went through a half dozen allows and ball sizes in the paste solder, and several different flux blends before we found what we needed. At least we started with a brand new Heller oven. :)

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There are two kinds of people on this earth:
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The first sign of insanity is denying that you\'re crazy.

I prefer 300 year old classical music. Too bad they didn't have xsistor radios back then.

I don't seem much of that with hand soldered equipment. I used to do warranty service on radios and such that were hand soldered in Japan in the 1960's. There were plenty of unsoldered connections and even parts that just fell out when we opened the box, but once they hit is with a soldering iron, it stayed put. However, that's with a limited number of manufacturers (about 4?) so others may not have been so neat.

It's very common in older xsistor radios. The radio gets stored somewhere with the batteries inside. The batteries leak. The rest you can figure out. I collect HP calculators. Many of those I purchase have severely corroded traces and contacts thanks to battery corrossion.

Never heard the scratchy noises while tuning a 365mmf tuning capacitor on an old AM radio? The noise you hear are tiny sparks in the bearings. Slightly conductive grease gets rid of that.

In the 1950's all speakers were paper cones. The coil to magnet seperation was fairly small in order to produce a high efficiency speaker. The cones are hygroscopic, warp when wet, and get easily misaligned. I have several old radios in my collection that need to be re-coned.

True. There's often a tiny schematic taped to the inside of the radio. Sometimes, the schematic actually matches the unit.

Nope. I don't recall the exact failure mode. Purple pleague sorta comes to mind on the early xsistors.

Sealing problems around the leads allowed water incursion, which rotted the wire bonds, was another.

Ummm... you're actually going to listen to AM radio? All I ever hear is talk radio. No music, unless you like the south of the border variety. Anyway, I clean all my repairs, so that the repair job

*LOOKS* like it's been repaired. Customers like to see their machines returned cleaned. Think of this as a restoration, not a fast fix.

Most of the rotted power cords I've had to deal with were RH, RHH, RHW or similar rubber cords. They were primarily attacked by the Los Angeles smog with a dash of UV embrittlement. However, many "plastic" cords didn't do much better. They didn't crack or crumble, but got very stiff. I recently recycled some cheater cords that are so stiff that they broke when bent. Incidentally, some commercial two-way mobile radios used rubber insulation well into the late 1950's.

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Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

I own about three hundred very old radios.Some of them are transistor radios, some of them are tube type radios.Some of them work ok.Some of them sort of work.Some of them don't work at all.Some of them are over fifty years old. cuhulin

Tin whiskers were not a problem on that vintage device. In 1957 I was working at a semiconductor facility on Boston's Rte 128 that was making transistors from scratch. And I do mean from scratch including crystal growing on up to testing. We were producing devices essentially by hand. Indium dots were diffused into germanium chips, finished assemblies were mounted on headers and connections were made by a large contingent of nimble fingered ladies.

Testing was straight forward for gain, H parameters etc. The challenge was getting mixers that worked. The test bed was a radio chassis with a socket in the mixer position. If the radio played, the transistor got shipped.

Charlie

I don't know. I've had several KLH Model Eight table radios, all well over

40 years old, and none had electrolytic problems.

Nah, I still use an old General Electric 8 transistor Am with 2 shortwave bands radio that was made in Utica NY. It's got a far better tuner than you typically get these days and still sounds quite good. Uses 4 c cells.