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The
pot is reassembled and the mains wiring connected, with all connections
shrouded.
All the pots will
be similarly serviced.
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At
this point I do a quick check on the wooden side base panels. These
can suffer from woodworm, though not in this set. Here I'm tighteniing
up the 4BA fasteners which secure to the panels to the chassis -
they invariably have settled and loosened after half a century.
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The
wires feeding the dropper mains taps are perished (as usual) and
are replaced with new neoprene rubber wire.
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Talking
of rubber wire, this set is generally fortunate; most of it is in
good condition and can be kept original. However it doesn't go amiss
to clean it with thinners to bring back the original bright colours
and then 'condition' it and maintain its suppleness for the longer
term by rubbing in Waxoyl. This will later dry off leaving it looking
like new.
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The
main HT electrolytics are re-stuffed. The old insides took some
getting-out believe me !
The
tag end of the old capacitor can has been sawn off - here it's been
perched back on top - you can probably spot the crack. Tiny holes
are drilled through the tag rivets to allow the new wires to emerge
and then be soldered onto the original tags. A circle or two of
aluminium tape secures the top and covers the crack. Then the electrolyic
can is mounted back in its original position.
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The
large above-chassis 0.75µF capacitor is an odd value, so has
to be exchanged for a 0.47 in parallel with a 0.22 - all 1000v -
1500v rated.
This capacitor is
connected between HT and heater circuit via a power resistor. It
is intended to reduce hum and works quite hard.
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We
shall service the rest of the main unit later, but for now we turn
our attention to the 'receiver unit' on its own little deck.
First,
the aerial input clamp is to be replaced by a Belling Lee coaxial
socket, to make it easier to plug in a modern aerial lead.
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There
is an isolating capacitor-to-deck on the earthy side of the aerial
input. For safety, it's important this is in good condition. Here
we see it being meggered - it turns out to be fine.
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Here's
the new coaxial socket mounted up to the original panel. It's desirable
to reinforce this with solder where the outer ring meets the base.
Otherwise it can loosen whenever the aerial cable gets yanked off
- as it invariably will be sometime...
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A
common problem point is the lead set which connects the receiver
unit to the main chassis. This wiring can often be perished. A close
inspection should be made for any cracked rubber at both ends.
Again,
with this set I'm lucky - this is quite good. It can be quite a
time-consuming job unsoldering the plug prongs, then replacing and
re-routing the bad wire.
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