Sinclair ZX81, Assembly Instructions Manual, Page: 2 / 43

IMPORTANT:
Read through the
instructions before you
start assembly.
If anything seems unclear or difficult, contact us for advice before
going ahead.
1. PREPARATION
You will need a clean, dry and well lit workspace in which to assemble your kit. If possible, try to find
somewhere where the parts can stay undisturbed in case you do not finish the kit all at once. It is a
good idea in any case to split the work up - say assemble the circuit board one eueninn_tben.tffst jt. and
put the case together the next evening You will need these tools
(a) A light electric soldering iron, say 15 to 25 watts with a fine tip
{b} Fine gauge solder with resin flux core; NOT acid flux.
(c) A pair of sharp sidecutters.
(d) A 'Pozidriv' screwdriver with a No. 1 point.
(e) A medium size ordinary screwdriver and/or a 4B A spanner.
The following items are optional, but useful -
(a) A magnifying glass for examining solder joints and looking for short circuits,
(b) Some desoldenng braid or other solder removing tool. Better still, take care that you put the
components in right the first time - removing them can be very difficult.
(c) A piece of foam is useful to stop components falling out when you turn the board over to solder
them
2. PRECAUTIONS
There are not many integrated circuits (I C s) in the kit, but they are all fairly expensive items and most
of them are susceptible to damage from static electricity. There is no cause for worry if a few
precautions are taken:-
(a) Use the sockets supplied with the k i t - never solder the I.C.s direct to the board - and keep the
I.C.s in their protective packing until you are ready to plug them in.
(b) Never insert or remove the ! C s or do any soldering with power applied to the computer.
(c) Use a soldering iron with a properly earthed bit.
<d) Carpets and clothing of man-made fibres, and synthetic soles on shoes, are prone to building up a
static charge. Earth yourself by touching a large object, preferably metallic, priorto touching the I.C.s If
you do get a shock, try changing your clothes or going barefoot (seriously'}
3. COMPONENT EDENTIFICATION
Before you start assembly, check the components against the component list (section 8) and make
sure you know what each part is. We have tried to cover all different markings of the components, but
variations are possible.
Note in particular that the computer's memory maybe supplied either as two 18 pin I.C.s (IC4a & IC4b)
or as one 24 pin device (IC4), and that assembly is necessarily different for each version.
Some components need to go in one particular way round -
(a) The I C s have one end identified by a notch, and/or a spot or dimpfe next to pin 1 (See fig. 1) Note
that all the ! C s face the same way on the board, i.e. with their notches towards the edge connector.
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