Heathkit AV 3U Service Manual

Page 2

COLOUR CODE FOR FIXED RESISTORS-(B.$.l852-I952)
COLOUR BAND MARKING

FIGI. COLOURED BAND
MARKING PREFERRED

THIS EXAMPLE snows /
A GRADEI. RESISTANCE

or 6,800 n :5%
BLUE( 6 )-J
GREYI 8 )
RED mo)
GOLD(:5a
{SALMON PINK (GRADE I.)

THIS MAY BE GENERAL aoov COLOUR FIG3.Boov TIP 5 CENTRAL BAND MARKING

AMERICAN RMA , JAN" 8: COMMERCIAL CODING "
FOR MOULDED MICA CAPACITORS

CURRENT STANDARD CODE

MOULDED FLAT CAPACITOR JAN.

CODE CAPACITOR
COMMERCIAL CODE

IST

{SIGNIFICANT

WORKING SILVER I5Y{$IGNIFICANT
I? FIGURE BLACK vous 2» FIGURE 7
IRMA BODY
BLACK -
(JAN) MULTIPLIER MULTIPLIER MULTIPLIER
2mr
C LASS

TOLERANCE 157

{SIGNIFICANT
FIGURE CHARACTERISTIC TOLERANCE

COLOUR CODE FOR RESISTORS AND CAPACITORS '

I .
COL. A. COLI E, COL, C. MULTIPLIER
In! 2nd elislorl
F In: ohms F

COL. D. TOLERANCE RATING

COL. E. TEMP.
fl Reliltorn ram :

n can ICXENT
u to! F mum :10 NC.

0 I

10

NO «Du
COLOUR

The Cnlour coding Ihuuld be read from 1m In 835:, In one; starting erm the end a_nd tiniahing'neu the mint;

Stand-rd: tolerance: {or relinurs am- wue-wound: 1%, 21.. 51., 107... cdmpdamdn. Grade I: 17.. 2%. 5%. Grade 2: 5%.
10%. 20%. (20% I: Indicated by m. (or 9') colour). Grade 1: ("high- Itanlity") cumpoiifion relistura are dillinguilhed by a m-
man-pink fifth ring or body colour. (Reference: 115.1552; I952 E.S.L).

N. a. High-Stability ReIIlluta supplied with this kit are not as a 1411: colour coded but enamzlled in one colour on which the value

In 0mm. printed in (ism... Capacitor! lupplild in m- ki: uaually have their capacity clearly marked In figural, Some Cap-
acitor: coded a. above me have addiudnal "voltage rating" codln.

Page 7

-m s

PRELIMHJARY NOTES AND INSTRUCTIONS

The Step-byrStep instructions given in this manual should be followed implicitly to ensure a minimum of difficulty
during construction and a completely satisfactory result, including many years of accurate, trouble-free service
from the finished instrument.

UNPACK THE KIT CAREFU LLY, EXAMINE EACH PART AND CHECK IT AGAINST THE PARTS LIST. In so doing,
you will become acquainted with the parts. if a shortage is found, attach the inspection slip to your claim and notify
us promptly. Screws, nuts and washers are counted mechanically and if a few are missing, please obtain them loc-
ally if at all possible.

Lay out all the parts so that they are readily available in convenient categories. Refer to the general information
inside the covers of this manual for instructions on how to identify components.

Moulded egg containers make handy trays for holding small parts. Resistors and capacitors may be placed in the
edge of a corrugated cardboard box until they are needed.

Use lockwashers under all screws and nuts. and also between controls and the chassis. When shakeproof solder
tags are mounted under nuts, the use of lockwashers is unnecessary.

Resistors and capacitors have a tolerance rating off 10% unless otherwise stated. Therefore a 100 Ki) resistor
may test anywhere between 90 and 110 KB. Frequently capacitors show an even greater variation such as -50% to
+100'7n. This Heathkit accommodates such variations.

Unless otherwise stated all wire used is insulated. Bare wire is only used where lead lengths are short and there
is no possibility of a short circuit. Wherever thereis a possibility of the bare wire leads of resistors or capacitors,
etc., shorting to other parts or to chassis, such leads must be covered with insulated sleeving.

To facilitate describing the location of parts, all valveholders, controls, tag strips, etc,, have been lettered or
numbered. Where necessary all such coding is clearly shown in the illustrations. When instructions say, for ex-
ample, wire to socket GS", refer to the proper figure and connect a wire to tag 3 of socket G.

Valvebolders illustrated in the manual are always shown with their tags numbered in a clockwise sequence, from
the blank tag position or keyway, when viewed from underneath.

All rotary switch tags are numbered clockwise when viewed from the rear of the wafer, i.e. the end remote from
the knob.

All resistors may be wired either way round.

All capacitors, excepting electrolytic capacitors, may be wired either way round unless otherwise stated.
Carefully letter and number tag strips, valveholders, transformers, etc. A wax pencil is ideal for this purpose.
when mounting resistors and capacitors make sure that the value can be read when in position.

Observe polarity on all electrolytic capacitors, i.e. RED : POSITIVE.

A circuit description is included in this manual so that those with some knowledge of electronics will be able to ob~
tain a clearer picture of the actual [unctioning of this instrument. It is not expected that those with little expel"
lanes will understand the description completely, but it should be of help in the event that they desire to become
more familiar with the circuit operation and thus learn more from building the kit than just the placing of parts and
the wiring.

Read this manual right through before starting actual construction. In this way, you will become familiar with the
general step-by step procedure used. Study the pictorials and diagrams to get acquainted with the circuit layout
andlocation of parts. When actually assembling and wiring, READ THROUGH THE WHOLE OF EACH STEP so that
no point will be missed.

A tick 0/) should be made in the space provided at the beginning of each instruction immediately it has been com-
pleted. This is most important as it will avoid omissions or errors, especially whenever work is interrupted in
the course of construction. Some Kit-builders have found it helpful in addition to mark each lead in the pictorial in
coloured pencil as it is completed.

GLOUCESTER

ENGLAND

DAYSTROM L

Page 14

12

( Connect a 4m resistor (YELLOW, VIOLET, BLACK) between LC} (5-2) and RI (S-l). -
(vf Using sleeving, connect the RED positive (t) lead of a 20 ~ 20 til 250 volt electrolytic capacitor to LCZ (N5).
9 v

(3/ Connect the other positive (+) lead of the same capacitor to LCl (NS).

(X Connect the negative (-) lead of the same capacitor to LDl (NS).

( ) Cut two 8%" lengths oi connecting wire and strip %" oi insulation (rom the tour ends. Connect one wire to LDZ
(NS)and the other Wire to LD3 (NS). Twist the wires together and dress along the edge of the chassis as shown
in Pictorial 3 Connect either wire of this twisted

pair to 539 (NS). Connect the other lead through 555
(NS) to 554 (5-1). See Figure 7.

(\K In a similar manner cut and strip two 3" lengths of
connecting wire. Twist the leads together. Connect

either leadof one sndot this twisted pair to 5139 (5-2)
and the other lead to 5135 (sez). Dress this pair along
the edge of the chassis. Connect either lead of the
other end to SA) (Ns) and the other lead through 5A4
(5-1) to 5A5 (NS). -

(J Connect a wire from 5A9 (5-2) to SC3(S-1)y NUMBERING ON 7-PIN NUMBERING 0N Q-FIN
/ V/SOCKET V/SOCKETi
( Connect a wire from SAS (5-2) to 504 (5-1).
Fl CURE-7.

(ta/Cut and strip two 4" lengths of connecting wire and

twist together, Connect either leadof one end to LDZ

(NS) and the other lead to LD3 (NS). Bend this twisted

psir around the cut-out in the chassxs and for the present leave free.
(i Count-ct a 4m resistor (YELLOW, VIOLET, BLACK) between LB}. (5-4) and LDl (NS).
( Connect a 47 resistor (YELLOW, VIOLET, BLACK) between LD3 (5-4) and LDl (NS).
(X Connect a wire irom LDl (5-5) to LBl (NS).
( Connect a wire trom R2 (5-1) to La (NS).
(/Connect a 10 KAI 1 watt resistor (BROWN, BLACK, ORANGE) between LC1(NS) to LCZ (NS).
(u/Connect a win: irorn ch (NS) to see (5.1).
(J Using sieeving. connect a 220 Kil resistor (RED, RED, YELLOW) between LCl (NS) and 537 (NS).
(V Connect a wire from SB? (5- Z) to SAl (5-1)..

i

( Using sleeving, connect the positive (it) lead of a 25 tiF 25 volt electrolytic capacitor to 5A8 (NS). Connect the
egative (-) lead to C2 (NS). Make sure this capacitor doesnot cover grommet GB. .

( Using sleeving, connect one lead of a 680i} resistor (BLUE, GREY, BROWN) to SAB (S- 2). Connect the other
lead to C2 (5-2).

(,4/ Connect a wire from LCl (5-4) to sci (NS).

(X Using sleeving, connect a 1 Km resistor (BROWN, BLACK, RED) between 5131 (NS) and LBZ (NS).

( Using sleeving, connect a 47 Ki: resistor (YELLOW. VIOLET, ORANGE) between 531 (5-2) and Lea (s_5)i
A Connect a wire from LBl (NS) to LAZ (NS).

(Vj/Using sleeving, connect a 150 KB resistor (BROWN, GREEN, YELLOW) between 5138 (NS) and LFZ (NS).

DAYSTROM LTD, - E n G L A N D

GLOUCESTER