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A new coaxial
aerial socket is fitted, replacing the original two-pin
socket. For additional safety the 'mains aerial' arrangement
is disconnected, in case the customer should be tempted
to try it in the future when receiving the British Heritage
Television Service. An 'H' aerial it will have to be...
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Here's the
new dropper in position along with a subsidiary tag board.
This had to be made up to mount the thermistor and an additional
dropping resistor.
A large amount
of neoprene rubber sleeves are used, both the guard the
dropper wiring against heat and to protect it where it passes
through apertures in the chassis.
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Having seen
what happened before, the prospect of the U801 rectifier
valve ever doing this again in future freaks me out. I don't
believe these are the most reliable of valves.
This set already
has two 1 amp fuses in the live and neutral mains inputs
in addition to a 3 amp fuse in the plug top. However to
be on the safe side I now add a another fuse - an in-line
315mA one in the anode feeds to the rectifier.
This means
that should the rectifier even get mildly overloaded in
future, this fuse will blow immediately.
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At last all
the waxed tubulars and Hunts capacitors underneath are changed.
All the resistors
are checked too. Five of them need replacement.
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The chassis
is now assembled above-decks. The focus coil and the LOPT
are mounted. The valves are plugged in. The scan coils are
connected up too, but the cathode ray tube cannot be mounted
until the chassis is mounted on the slide-out cabinet section.
This will have to wait until the flock-covered screen mask
is restored. That's now the next job.
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The old rubber
screen mask is cracked - a very common phenomenon. First
it is strengthened as much as possible by trickling superglue
into the many cracks and then pushing them closed.
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Then
a flexible skin of Evostik is applied to bridge the tops of
the remaining cracks. This has to be done several times over
before it will conceal the cracks properly. |
Finally, the
mask is re-flocked.
The actual
process is difficult to actually do and photograph at the
same time!
However, first
a special coloured adhesive is liberally brushed on. Then
the nylon flock is 'puffed' on everywhere as forcefully
as possible from the squeezy bottle supplied with the kit.
Some of it sticks to the adhesive coating. The residue is
shaken off and saved for later re-use.
The adhesive
holding the flock was left to set, then the whole thing
done all over again - for an even better finish.
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Time to take
a first look at the tube. This is cleaned. First, cellulose
thinners is used to produce a highly insulating surface.
Particular attention is paid to the final anode connection.
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Then anti-static
foaming cleaner is applied on and around the screen area
(only). This is necessary to prevent later 'beam repulsion'
effects whenever the set is switched on.
This is caused
by a standing charge building up on the screen which cannot
escape. The anti-static spray will allow it to leak away.
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Two double
canvas straps hold the tube to the mask - under spring loading.
These (and the springs) are now washed in detergent.
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Once dry,
they are mounted up to the tube. The rubber mask sits underneath.
It's necessary to centre this carefully against the screen
aperture beneath so it looks right...
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And this is
the effect.
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It is then
decided that the appearance of the tube mask is not quite
good enough. It is removed for tinting. This is achieved
by a series of very light, distant puffs from an
aerosol paint. Too much paint at this point would have ruined
the flock. But the correct amount of paint actually adds
to the appearance of the flock.
A little paint
will also have the beneficial effect of better binding the
flock in future. Such masks can loose some of the flock
over the longer term, causing a powdery deposit on the inside
of the screen glass.
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Another point
which fails 'quality check' is the appearance of the soldering
at the tube base socket. This is removed, all the solder
removed from the tags and the whole thing done again from
scratch.
Otherwise,
the chassis is now complete. Tomorrow, we switch on !
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But first,
here's something else that has been overlooked. The original
loudspeaker lead found with the set was an old piece of
lighting flex. This was duly replaced by period cable, but
I hadn't terminated this with the correct connector to plug
it into the speaker. The connection is actually to the primary
winding of the output transformer, which sits on the speaker.
A suitable
connector is now found in the stores and soldered on.
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