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A customer dropped in a small
receiver the other day and it went into the backlog to be dealt
with when the spirit moved me or otherwise.
"Otherwise", usually means that the owner telephones
me to ask on the progress, and this was the position here as
the owner did indeed call after only a few days.
I scrutinized the little set during the phone call, which was
really concerned with non-escalating costs. It was more of a
"nice to have receiver" fitting into brackets somewhere
within the cabin of the small boat.
Keeping costs within reason is is not an unusual type of request,
as it's a simple matter to multiply a living wage hourly rate
by a few hours and arrive at a figure well in excess, of a cheap
replacement (no matter whether it's a receiver or some other
piece of consumer equipment).
It's rapidly becoming obvious that the
only items worth the true cost of repair, that come my way these
days, are parts of complicated items such as large industrial
machines, or parts of the general fabric of a building, such
as a lift.
All that having been said, I like fiddling
with interesting things and this little receiver promised some
interest.
So it was then that, having recently finished sorting out a computer,
I laid the little receiver on the bench and reached for my screwdriver.
Immediately before this I'd connected
a 12-volt power supply to the set after wondering vaguely whether
the blue and brown mains lead was really for mains connection
or just happened to be available to the manufacturer when he'd
made up a power lead. The give-away was a small label on the
rear proclaiming use of a DC supply of between 12 and 30 volts
or so.
I must admit that I used logic to decide on the polarity, choosing
brown for plus.
The receiver front panel had come to life and the display showed
a number like 268 but there was silence. Does it have a loudspeaker?
I looked around for a grille before seeing a little switch labelled
SPKR. Pressing the switch upwards (upwards?) resulted in a loud
noise like interference from a million television sets. I found
a long wire aerial and poked it into various sockets before being
rewarded by a change in the background cacophony. Twiddling the
tuning dial to 198 then resulted in Radio 4 muting the noise
and I heard speech.
What was the compliant?
"No FM", I recall was the message I'd had.
I switched the knob to FM and a number showed in the display.
"10.7", it said. Odd that sounds like the IF frequency
of an FM receiver.
I switched back to medium waves and tuned in Radio 5 Live. That
sounded OK apart from then fact it was a bit subdued. Short waves
also produced some signals but switching back to FM did not.
True that on the second attempt the display showed 95.7 rather
than 10.7 but still no sound.
I twiddled some more and decided that
the problem lay with the wave-change switch. It felt ever so
unpositive, and electrically certainly dodgy as indicated by
inconsistent readings on the display.
It was at this point I decided to fill in the next 30-minutes
with a quick repair of the receiver. A squirt of switch cleaner,
replace the screws and Bob's your uncle. A "Low Cost Repair",
as the owner had requested.
I removed the screws, revealed the switch,
and squirted switch cleaner. Not easy as the switch was a peculiar
affair with enclosed wafers.
I powered it up. It was much the same.
Intermittent dial readings. But wait; as I looked inside the
set and waggled the wave-change switch knob I noticed the switch
seemed to have a kind of inbuilt delay and a mind of its own.
It was only with the greatest reluctance that the certain sections
of the switch actually responded to movements of the knob.
I donned my magnifying headset and soon found that the section
of the switch nearest the knob was broken.
I've gone this far I thought, so I might as well bash on and
spend another 30-minutes or so.
An hour later I'd dismantled the set.
It was typically British in design. Absolutely no thought to
servicing. The case was attached by various electrical fittings
to the chassis and couldn't be detached. The front panel was
merely a plastic cover and to go further meant that the set would
have to be taken entirely to pieces.
So it was then that after another hour
it was completely in pieces.
In fact it was only now I could see that to actually proceed
would involve unsoldering the switch from the printed circuit.
Only 24 soldered pins to each wafer and a mere eight wafers.
That's 192 solder joints. Not too long with my unsoldering tool
I imagined. At least the holes weren't plated-through. Being
a British-designed set it had that in its favour.
Now I don't know if you've ever tried
to remove a soldered-in device. Take a three legged transistor
for example. Every leg has to be entirely free of solder otherwise
one cannot pull it away from the circuit board.
This device had 192 legs. It took ages with a solder wick and
a strong magnifier before I'd freed all 192 legs sufficiently
for me to lever the switch away from the board.
What I removed was in a very sorry state indeed.
The old paxolin Yaxley switch used to
work for 60 years and no doubt longer when they get the chance.
Sometimes one will break but that's often due to rough handling
not the basic design.
This modern equivalent of Yaxley's design was absolutely awful.
Each wafer relied on a flimsy plastic disk to pass turning movement
to the contacts. Worse. The end operated by the knob relied on
only half the thickness of the section, not only to rotate the
contacts, but also to pass turning movement to the whole switch.
With years of use and stiffening action,
the end plastic disk had more or less disintegrated. At least
the bit that relied on passing energy from the knob to the remaining
sections. All the others, under less stress, were cracked in
varying degrees indicating to me that the design was flawed.
My supplier's catalogue was strangely mute on any rotary switches
let alone this complicated beast.
I looked at it wondering how I could cut my losses.
If this was an essential part of a lift,
I would dutifully search the Internet for a manufacturers' catalogue
and a stockist, but that would take time and lead to an expensive
conclusion.
As all eight sections of the switch
were identical maybe I could move them around. Put a good one
at the end and the others further along the shaft?
I set to and after 20-minutes had the switch in pieces in front
of me. At least most of it, as at one point there was a sort
of flicking noise and bits flew in all directions.
I looked half-heartedly on the floor amongst the debris of earlier
jobs and retrieved a tiny ball-bearing.
I t was at this point I'd realised why
the set reacted strangely when the wave-change knob was rotated.
Some of the wafers seemed to have a mind of their own, sometimes
rotating with the rest, sometimes not and sometimes grudgingly
moving only halfway. Because the plastic had broken on most of
the wafer assemblies, the two metal wipers were not always pressed
against the corresponding metal inserts for the switch positions.
I worked out a solution so that at least
the set could be used. If I added a shim between each wafer assembly
the parts would be forced together. Depending on the damage to
the assembly I would either add a wide shim or a narrower shim.
I went off in search of something suitable.
I came up with some of those square
nuts used for coach bolts. I found seven that were just the right
thickness for the narrower shim and by adding an extra washer
a thicker shim could be fashioned.
I carefully reassembled the switch.
That is until the final section when I refitted a tiny spring
and a ball bearing. It was at this point I realised that two
ball bearings were required, one either side of the spring, which
fitted inside a hole in a plastic plate. The bearings located
in indents so that precise switch positions were made.
There had been a sort of subdued rattle
from somewhere on the floor. Underneath the bench was an old
computer chassis so I lifted this and shook it. A few odd screws
fell out. I moved the chassis and detached my specially strong
horseshoe magnet from the side of the electric fire where I won't
forget it.
After brushing the magnet around the
floor for a few moments it had attracted numerous computer screws,
bits of wire and lots of iron filings but no ball bearing.
I wondered what to do next as the future of the whole project
seemed now to rest on a ball bearing about a millimetre in diameter.
I have a plastic bag containing an assortment
of these kinds of things but Goodness knows where I put it. I
also have a collection of old Yaxley switches with the odd ball
bearing but I couldn't remember where I put them either.
I went outside and looked in our old
garden shed, after finding the key and getting wet feet as I
approached it via the long grass. Lots of bicycles, a lawnmower,
a shredder and a mountain of perilously stacked boxes bulging
with useful stuff.
I pulled out a steel toolbox with the vain hope of finding a
stray ball bearing in its recesses. All I discovered was a lot
of rusty tools and a red tubular thing labelled "parachute
distress flare". I vaguely wondered if these were allowed
on 5th November? Maybe not near the South coast I thought, but
what about somewhere inland… like Birmingham? There can't
be too many coastguards on the lookout in Birmingham? I put it
back and dropped the old toolbox back on the floor, locked up
the shed and went back to the workshop.
Another, wider scan with the magnet
revealed nothing except some more computer screws so I thought
very hard. Where might I find a small ball bearing?
How about a little ball of solder? I'd tried that once but it
was too soft.
What about the front fork of a bicycle? I had memories of spilling
dozens of ball bearings the first time I slackened the large
nut under the handlebars of my old bike, maybe 55 years ago.
I had found several bikes in the shed
but those were in quite good condition so those I ruled out.
I trudged outside again in the steady drizzle and lo and behold
behind the dustbin in the veritable mountain of rusty bits of
old Landrover chassis I found the frame of a bike.
I pulled it out. The front forks were present. A 6-inch section
of the frame had been neatly removed. At first I couldn't remember
why. Then I remembered I'd used it to repair my Rover 820. It
was now somewhere in the cooling system.
I looked at the top nut. It was very rusty but after thumping
it with a hammer and heaving on it with a large pair of pliers
it moved. Twenty minutes later I'd retrieved a couple of ball
bearings. Unfortunately they were far too big.
Somewhere in the dim recesses of my
mind I recalled I'd had this trouble before. What had I done
then? After bashing a pedal off the bike and giving up on the
centre bracket I remembered where I'd found a miniature ball
bearing once before.
I looked around the workshop and picked up an ancient hard drive.
The thing was extremely tightly held
together with torx screws, but luck was with me for once, and
I actually found my box of miniature torx screwdrivers and set
to work dismantling the thing.
There were dozens of screws, followed by a lot of shiny disks,
a set of heads and finally a cylindrical lump containing an armature.
I looked at the aluminium cylinder. No obvious means of taking
it apart so I bashed it with a hammer and after raining a multitude
of blows extracted not one but two miniature bearing races.
I prised away the seals and underneath
I could just see some miniature ball bearings.
Next I had to get the inner and outer rings apart.
They looked pretty solid.
I decided to use a proper engineer's bench vise and a press made
from an old screwdriver.
My vise is unfortunately at the back of my son's shed, in which
rests, and entirely occupies, an old car in the process of being
taken apart for spares. I found the shed key and squeezed past
the remains of the old Sunbeam Rapier to the bench vise.
I fiddled around and got precisely nowhere using a delicate approach
so I just squashed it until it broke.
Unfortunately it broke with a sudden
bang into several pieces and all the ball bearings flew into
the air and landed in the innards of the partly dismantled Sunbeam.
Lost forever.
I looked at the second, identical race.
I couldn't afford the time to find a third so this one had to
yield the necessary parts.
I squashed it… but this time I placed my fingers either
side to lessen the explosive impact as the cast steel shattered.
It worked and, when I cupped my hand under the remnants, a few
small steel balls dropped in.
Clutching the things firmly I squeezed
past the car back to the drizzle and locked up the shed.
The ball bearings from the hard drive
were exactly the right size.
I dropped one into the switch on top of the tiny indent spring
and very very carefully pressed the parts together until there
was a click and a few moments later after inserting the shims,
pressing the sections onto the shaft and finally tightening up
the longitudinal securing screws the switch looked OK but was
a trifle stiff to operate. Slightly slackening the screws reduced
the pressure and it worked normally.
I looked at the set of solder tags.
I now had to thread 192 pins back through the holes in the printed
circuit board.
I didn't feel like tackling this, and anyway as it was then 6pm,
I placed it on the bench, turned off the lights and went in.
I refuse to work after 6pm unless it's a really interesting job.
This wasn't.
Next morning, after toast and coffee,
I threaded the 192 pins and soldered them in place. It took ages.
It's bad enough inserting the 14 pins of an integrated circuit
back through holes only just large enough and half packed with
old solder.
Now that the switch was back in place
I reassembled the radio. That is, I went as far as screwing all
the parts together before I found that the last two assemblies
wouldn't fit together.
It's a British-designed radio and the mechanical design is absolutely
awful. It's one of those cases where all the bits have to be
presented together at about the same time and jiggled. Eventually,
after unscrewing the parts for a second time, then reassembling
it in an illogical manner, it was back in one piece.
Finally I slid the outer case over the
chassis. As I did this I heard a little rattle and what did I
find rolling around inside the case? A tiny ball bearing.
I sighed, put it in a plastic bag with the rest of my new collection,
and carefully placed the bag in a little drawer marked "24-volt
Relays". If I knew where I'd put my labels I would have
made a new one but they went missing a few days ago.
Did the radio work?
Yes, it did, but goodness knows for how long before the plastic
bits in the switch finally disintegrate totally.
The price was £25 which works
out at around £3 per hour. |
return to customer
repairs