Sinclair ZX81_Assembly Instructions.pdf

(721 KB) Pobierz

This technical manual was OCR'ed for the

Sinclair world by Andy Dansby.

andydansby@yahoo.com All intellicial

information contained inside this technical

manual is the property of Amstrad.

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.

(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.

them

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.

<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.

Although the I C. sockets do not need to go any particular way round, you may like to put the bevelled

corner at the notch end of the I.C. position as a reminder, since the semicircie printed on the board will

be covered by the socket in some cases.

(b) The diodes (prefix D) have their + end identified by the band painted on the body - or in the case of

components with several bands, the + end will be the widest band. This corresponds to the flat bar of

the symbol printed on the board. (See fig. 2).

usually longer. (See fig. 3).

(d) The transistors (prefix TR) go in the board as shown by the picture printed at their positions - i.e.

with their rounded corners facing the edge connector.

(e) The jack sockets and modulator need to have their business ends (i.e. where the plug goes in)

facing outwards, away from the components. This should be obvious by inspection of the board and

case.

(f) The regulator (REG) and heatsink need to go in a particular way round -just follow fig. 4.

(g) The keyboard connectors KB1 & KB2 have their pins offset from their centre line, and KB1 goes

the opposite way round to KB2. Make sure that in each case the body of the connector covers up the

component number on the board. (See fig. 5).

, . ...

... . . - , . . . .

. ..

end marked wltn a whlte dot Thls snould

at tne

(h) The resistor packs (prefix RP) have a 'common'

9°

end marked with a 'C' on the board.

(i) The single resistors, the rest of the capacitors, and the filter X1 may be put in either way round.

CIRCUIT BOARD ASSEMBLY

The circuit board will be supplied with one side printed with all the component locations - this is the

side the components go. This printing is reproduced as fig. 6 (See reverse side of sheet) since some of

the markings will be covered by components. All soldering is done on the other side which is coated

with a green solder resist - this keeps the solder away from where it is not needed. The exception is

the edge connector area which should be kept free of solder to ensure reliable connection to the RAM

pack or printer if they are used, We suggest you assemble the components in the following order,

although it is not compulsory -

(i) Resistors, capacitors and 1C sockets - do not plug the I C.s in yet.

(ii) The diodes and transistors.

(iii) The 'large' components: the sockets, keyboard connectors, modulator, the regulator and

heatsink.

(iv) Finally plug the ! C s into their sockets.

The general procedure for each component:-

(a) Identify the part and its position on the board and insert it into the appropriate holes, bending the

leads if necessary. (But see later). In the case of components with a number of pins, make sure that

they have all gone through their holes.

(b) Hold the part in position - if you bend its leads to do this, do not press them fiat onto the board as

this will make them difficult to cut and will encourage short circuits.

{c) Solder all the wires on the 'green side' of the board and, if they are long, trim them with the side

cutters. No lead should stick out more than about 3mm or V^'from the solder side.

Some components need more detailed explanation:-

(a) The capacitors are represented by a capacitor symbol on the board, rather than a box as the rest of

the components are. Fig, 7 explains how they fit in the board relative to the symbol.

(b) There are four oblong boxes labelled R7-R10, R11-R14, R18-R22and R23-R26. These all contain a

row of resistors standing 'on end' as in fig. 8. Take care when mounting these: the length of bare wire

up the side should not be allowed to short against anything else

use only the holes corresponding

to the smaller box.

(d) As previously mentioned, IC4 may be in either one or two packages, Only the appropriate 1C

sockets will be supplied, so make absolutely sure you know which version you have got before

proceeding.

IMPORTANT:-

If you have the 24 pin 4118 in your kit, a short wire link should be inserted in the holes

at position L1 Use a component lead off-cut for this. DO NOT do this if you have two 18 pin 2114s, and

do not put anything in position L2.

(e) When mounting the regulator, do not bend its leads too close to the plastic. Bolt it down firmly with

its heatsink

before

soldering.

(f) Put the modulator's wires through the holes marked "Fr/UK1" and "UK2" Put each lead through

the hole it is nearest to: do not cross them over Do not try to bend the thick pins on the modulator:

hold it in place by hand whilst soldering. The black card trim is a push fit over the aerial socket.

(g) The I.C.s will have their pins splayed out slightly and you may need to push them inwards slightly,

e.g. by pressing against a flat surface, before they will fit the sockets. Make sure that each pin has in

fact gone into its respective socket and that none are curled up under the I C.

5. TESTING

The completed board should now be checked

very

thoroughly for stray blobs of solder, dry joints, leads

not trimmed, etc. Also make doubly sure that all components are in the right place and the right way

round, and that the "stand up" resistors are not touching anything else. If everything seems in order,

the board may be tested before you put it in the case. Rest the completed assembly on an insulating

surface (e g these instructions) making sure there are no wire offcuts or similar trapped underneath.

The keyboard's "tails" may now be plugged carefully into their connectors: the one with 5 stripes goes

into KB1, the one with 8 stripes goes into KB2 These "tails" are quite fragile, so handle them gently.

The keyboard itself should sit (the right way up) just in front of the circuit board-

Do not

remove the

backing paper from the keyboard at this point.

You may now connect the computer to the T.V. and power supply and try it o u t - s e e the main

instruction manual for details

Once you are sure the computer is working correctly, put it in its case - see section 7. Do not strain the

keyboard connections unnecessarily by using it uncased.

6. FAULTFINDING

Experience with the ZX80 has revealed that the majority of faults on kits are due to bad soldering. If your

computer does not work, switch it off and CHECK IT AGAIN. If you find a bad joint or short, shame on

you i You should have checked more closely the first time. If you are sure the fault is in the circuitry, try

these tests--

(a) If the computer does not work at all, leave it on for a couple of minutes and feel the regulator - it

should be getting warm. If not, check the power supply, and that the plug is in the right socket (the one

nearest the keyboard). Otherwise, look at the connection to the T.V. and make sure it is tuned in

properly-try between channels 33 and 39 UHF.

(b) If the computer works and then goes off, and the regulator gets very hot, it isn't bolted to the

heatsink properly.

"tails" are properly in their connectors, and not twisted in anyway Also make certain that the diodes

and the keyboard connectors are all the right way round.

(d) If the screen goes clear but there is not a cursor, try disconnecting the power supply and waiting a

few seconds before trying again.

(e) If horizontal black and white stripes pass through the picture, suspect the power supply. If you are

using your own supply, it may need to be better smoothed (if the computer is otherwise working) or of

a slightly higher output. See the power supply specification (section 9).

7 CASE ASSEMBLY

(i) Take the case top - the part with the raised "Sinclair" logo and "ZX81" printed on it - and feed

the "tails" of the keyboard through the slot at the top right hand corner of the keyboard recess. Do not

remove the backing paper form the keyboard yet, just locate it in the recess: see fig. 9. Hold the

keyboard temporarily in place with a rubber band or a little sticky tape.

(ii) Hold the circuit board as in fig. 10 with the keyboard connectors next to the slot with the "tails"

poking through, Plug the "tails" into their respective connectors as shown in the diagram, and turn the

board over so that the components face into the case top behind the keyboard.

NOTE. Special attention must be made to ensure that the correct length of screw is used in the correct

hole. The short screws are yellow in colour, the long screws are black in colour. Fig, 11 shows where

Sinclair ZX81_Assembly Instructions.pdf

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika: