Heathkit AW 1U Assembly Manual

Page 2

'/ ADVICE Oi. CMU'JGE

Colour Conig of Mains Cables.

ELLI. Government have decided to make regulations requiring the core colours of three-
core flexible cables to comply with the following international coding recently agreed
by most of the countries in Europe:

Green and Yellow striped core EARTH
Brown core LIVE
Light blue core NEUTRAL

Under the old system the colour code was Green -EARLH; Red : LIVE; Black .. NEUTRAL

I When connecting, the: mains cable in your kit, please amend. the appropriate step/s in

your manual as followsz~

Amend Green to read Green and Yellow stripe
Amend Red to read Browno
Amend Black to read. Light blue.

A.09C, 6-10.69/Geno

192M; 5 Manny.» [[10 T! .!'! Ht! '1 un nlurrnnflhl K ,1. l . *7

Page 17

w n

NOTE: When solderlng the preciswn rc5istors in place, hold theleads with a clampDr piiers to keep the components
from becoming excessively warm. Excess heat may cause the resistors to change value.

(/7 Identify the RANGE switch and position as shown in Figure 12.
(/1 Cut a piece of wtre to a length of 2". Strip both ends and connect one end to 11(Ns). Leave the other and free.

(/) In a similar manner, cut a piece of wire to a length oi 3". Connect one end to J1
(NS). Leave the other and free.

(/1 Connect a i imprecision resistor from ii (5- 3) to J2 (Nst (Use sleevingi)
(x) Connect a zioziz preciston resistor from J2 (5»2) to J3 (NS). (Use sleevmg.)
(4 Connect a 683&\l precisxon resistor from 33 (5-2) to J4 (NS). (Use sreeving.)
(z) Connect a 21.62 KAI precision resistor from J4 (5-2) to 15(NS). (Use sleevmg.)
(A Connect 3 (>6. 38 K32 premsion resistor from J5 (3-2) to .16 (NS). (Use sleeving.)
(i/) Cut a piece of wire to a length of 17. Connect one end to J6 (572) Leave the

l
other end lree. tuna: szVCH
FIGUREIZ,

t/r Cut the lead a! one end of a .05 or capamtor to a length oi 5/3", Connect this
end to J7 (S-l). Leave the other and free.

(/) Mount the RANGE switch at location J1 orienting it as shown. Observe Figure 6 for mounting detailsi

CONTROL MOUNTING. FIGURE.6

LOCKWASHER
-- -||-|I-II- -
NUT. n n CONTROL
FLAT WASH in c-_-.

LOCATING PEG
PANEL on CHASSIS

(/) Identify the LOAD SELECTOR switch and position as shown in Figure 13.

(x) Cut a piece of wire to a length of 3. Strip both ends and connect one end to L2
(NS).

(2) Connect a 70752 precision resistor from L2 (8-2) to L3(NS). (Use sleevang.)

71/

(/) Connect a 37679 precision resistor irom L3 (5-2) to L4 (Ns). (Use sleeving.) "

(4 Connect a 16519 precision resistor from LA (5-2) to L5 (NS). (Use sleevmg.)

Connect a 38759 precision resistor from L5 (5-2) to L6 (NS) (use Sleeving) and
L7 (NS) directly underneath sztrcwn sinCN
F I GU R E | 3 V
(,4 Cut.a piece of wire to a length of 3". Connect one and t0 L6 (5- 2) and L7 (S- 2) Leave the other end free.

(/I Mount the LOAD SELECTOR switch at location L. Observe Figure 6 {or mounting details.

GLOUCESTER

YSTROM -ENGLAND

Page 24

1e-m

AUDIO GENERATOR, , 5-88 on 5-33

FIGUREIB.

The instrument can be left bridged across a line without indicating, if necessary, by placing lhe LOAD SELECTOR
switch in the OFF position, This disconnects the meter amplifier from the circuit, leaving only the compensating
resistors connected across the load circuit.

CAUTION: The LOAD SELECTOR switch should never be rotated When energy is applied to the wattmeter inputr if
it becomes necessary to change impedance setting, the input to the amplifier under test should be reduced to zero,
or the amplifier turned off. Damage to the meter movement/needle due to violent hammering against the steps will
be avoided if this precaution is observed.

Highly accurate monitoring of output level for recording purposes etc. can be accomplished by connecting the watt-
meter across the amplifier output leads and setting the LOAD SELECTOR switch to the proper impedance under
EXT. load. The circuitry is such that the instrument makes an excellent :13 meter.

READING THE POWER SCALES

The meter power scale is marked from 0 to 50 watts for power measurements. When making measurements on the
5 mW (milliwatt), 50 mW or 5w scales, read the scale and adjust the decimal for the correct wattage.

Example: Using the 500 mW range, the meter indicates 10. For correct power, move the decimal point two places
to the leit, or .1 watts (100 mW).

On the 50 W range, the meter reads direct. For each anti-clockwise position of the RANGE switch, move the deci~
mal point one place to the left.

USING THE DECIBEL SCALE

Because the human ear does not respond to the volume of sound in proportion to the signal strengih, a unit of mea-
sure called the "Bel" was adopted. The "Bel" is more nearly equivalent to human ratios. Normally the reading is
given in 1/10 of a "Bel or "decibel" (dB).

Different Signal levels are adopted by various manufacturers as a standard or 0" decibels. The trend within the
last few years has been toward the use of a l milliwatt into a 6009 load as "0" dB. This reference has been given
a special designation of "dBm". The Heathkit Audio Wattmeter is calibrated to read in "dBm when used as a 60032
load.

When using the AW-lUtor dB measurements, adjust the RANGE sWitch Until there is a reading on the decibel scale.
The meter reading is then either added to or subtracted from the RANGE indication.

Example: RANGE +20 dB, meter indicates +5 dB, actual value is +25 dB.
RANGE -10 dB, meter indicates +15 dB, actual value is +5 dB.

Since the decibel is a power or voltage ratio, it may be used as such Without specifying the reference level. Thus
for instance, a fidelity curve may be determined on an amplifier by feeding in a signal of variable frequency but
constant amplitude. As the input frequency is varied at constant amplitude, the output level variation may be noted
directly in dB above and below the specified reference level.

COMPLEX WAVE FORMS
This instrument, like most AC voltmeters is calibrated to read the Root Mean Square (RMS) value of a pure sine

wave. This is 70. 7% of the peak voltage.

ENGLAND

YSTROM LTD.

GLOUCESTER