Heathkit V-4 User Manual

HEATHKIT

MODEL V-4

VACUUM

TUBE

VOLTMETER

Power

Overall

Kit

Requirements:

Size:

Shipping

Meter:

Multipliers:

Power

Batteries:

D. C.

Supply:

Voltmeter:

Electronic AC

Electronic

Ohmmeter:

Weight:

6

Input

Sensitivity:

Circuit:

Voltmeter:

.

.

Ranges:

Resistance:

Ranges: .

6

....

Ranges:

6

Circuit:

SPECIFICATIONS

. 105-125V 50/60

10"

.

high x

pounds

. 8

"

Streamlined case with

4f
ment.

Carbofilm

-

1

6SN7

-

1

6H6

Power

2-

li

.

0-3,

10, 30,

accessory

With

megohms

. 11

.

110 megohms with

3,666,666

. Balanced

.

0-3,

10, 30,

scales reading

.

.

Diode

, Scale with

xlOM,

internal

with

Cycle

6"

wide x

precision

triode meter

Twin

Twin

diode

transformer

standard

Volt

300,

100,

probe to 3,000

megohm

(1

ohms per

bridge

with adjustable

Meg.

xl

(push-pull)

300,

100,

R. M. S. (.707

ohms

10

Measures

battery.

10

AC,

deep.

5-P

200

type--l%

bridge.

rectifier.

AC

selenium

and

flashlight

1,000

in probe) on

accessory

volt on 3

using twin

Volts

1,000

compensation.

center xl,

.1

Watts.

microampere

tolerance.

rectifier.

cells.

volts

Volt range.

ohm

full scale.

and

10,000

all ranges.

probe.

triode.

full scale on

negative peak).

of

xlO, xlOO, xl,000,

to

1,000

move-

Volts.

linear

megohms

ASSEMBLY

OF

THE HEATHKIT

MODEL

V-i

VACUUM TUBE

VOLTMETER

It

is not difficult to construct

this instrument If the

instructions

are carefully followed.

Do not

rush

the

construction,

Take time to do a

first class job to Insure years

of troublefree

operation.

Hurried work

increases

the chances of mistakes

and

subsequent

difficulties.

THEREFORE

READ

THIS MANUAL FULLY

THROUGH

BEFORE STARTING THE

ASSEMBLY.

Begin

by checking the parts

against

the

parts list. Identify each part,

using

the charts on

the

inside of the cover

of

this manual where necessary.

Thus,

you will avoid throwing away

any small

part*

with

the packing,

Familiarise

yourself with the

layout

by studying the pictorial

diagram

and the photo prints.

Then

proceed by

following

the step-by-step

assembly

instructionSr

Read the note on

soldering

on the inside of the batik cover.

Make a good mechanical

joint of each

connection

with clean metal

to

clean

metal- Use only good

quality

rosin

core radio type

solder

.

Pastes or acids

are difficult to remove and minute?

amounts left combine with

moisture

from the

air

forming a corrosive

product. Weeks or months

later

corrosion

may result f n untimely

fail-

ure.

This

corrosive

product is

also

a fairly good conductor and may

cause

short circuits which

damage the

meter,

NOTE: ALL

GUARANTEES ARE VOIDED

AND WE WILL NOT REPAIR OR SERVICE

IN-

STRUMENTS

IN WHICH ACID

CORE SOLDER OR PASTES

AHL

USED,

Small changes In parts

may be

made by the Heath Company.

All

parts supplied will work

just

as

well as the

part

for which It was substituted.

All

substitutions will be of equal

or

better quality

than the original

f

and will be

made

in order that a minimum

delay will

occur in filling

your order,

The precision

resistors

are marked with K

=

1,000

and M

=

1,000,000,

Thus

t

a

resistor

marked

9QK

=

90,000

ohms and one

marked

G-9M

=

9,900,000

ohms or

9-9

megohms.

The chassis and panel are

wired

separately as far as possible. Then

they are fastened together

and the wiring is

completed-

step by Step

assembly

(5)

means solder the connection

(NS) means do not solder yet

l.

Fasten the

tube

sockets (OS4)

with

socket rings

(04

3

J to

the c hasIs (V52B)

with

the key

wavs towards the nearest

edge

of the chassis. The end of the ring

can be held In

the groove in the socket

and the rest of the ring

can

then be forced over the socket

and into the groove with

a screwdriver. Mount

the two calibrating controls

(V 24)

with a control nut and a control

loekwasher

between

control and

chassis-

Temporarily

mount the zeru

ad-

just

controMV03.)

and the ohms

adjust control

{V25J

with

a control

nut and a control lockiwasher

between

control

and chassis. Mount

the

AC balance control (V99) with

a control nut and a conlrol

loekwasher

between control

and Chassis.

2-

Install the three

f

rubber grommets

(035)

In

the

chassis

holes provided. Mount

the

power

transformer with the twolejid*

through

the groin met near the front and the? four

leads through

ihe grommet near the rear of the chassis.

.Between

the tube sockets, use a

6-32

x

%

screw

with

a single

terminal

strip

{Q38)

and a solder lug under the

nut.

On the other side, uac a

G-32. x

1

screw, and place the selenium

rectifier

(V97) and a loekwasher under

the

nut.

Cut

transformer leads to length and connect a s follows:

One- yellow

lead to solder lug (MS) be-

tween tube sockets-

Other

yellow lead lo pin 1/7 on SH6 socket {MS), One red lead to

single

terminal strip (NS). Other red lead to lug on

selenium

rectifier

nearest chassis (S). A bare

wire through pin

#1

(3)

fr2

(£)

t'4 (NS) and tf&

INS)

on 6HG socket, A bare

wire

to

pin

#4

(NS)

on 6116 socket and to

solder

lug (NS)- A

bare wire to pin

CMS)

on 6SN7 socket and to solder

lug (S). A wire to pin #7 on 0H6 socket (S), and to

pin #7 on 6SN7 socket (NS), A wire to lug

on selenium rectifier farthest from chassis (NS) and through

pin

#5

(S) to pin

+2

(NS) on 6SN7

socket,

A ,003 condenser (V2<5) to pin

#4

on

6H&

socket (S),and with spaghetti over the lead to pin

#4

on

6SN7 socket (NS). A 4 7 OK resistor

(013)

to pin

#8

(S) and pin

*6

(NS)

on 6H& socket. A

10 meg resistor (CIO) to pin

*5

(S)

and

to

pin #3 {NS). A 20K resistor (V22)to single terminal

lug {NS), and to pin If 8

on

6SN7

socket

(NS). A

meg resistor (O10) to pin f

1

(S) and pin *&

(NS)

on 6SN7 socket. A 1SK resistor {V23) to pin #S <S> and to pin

#3

{5)

on 65N7

socket.

A 2K Resistor (G15) to pin A3 on 65N7 socket (ft5)and with

spagetti

over

the lead to lower ter-

minal of aero adjust

Control

($}. A

resistor

{015)

with spaghetti over both leads to

upper

terminal o£ zero adjust control

(Si

and to pin KG on 6$N7

socket

(NS).

A 47K resistor (A

10)

with spaghetti

over

both

leads

to

center terminal of zero adjust control

(5)

and to single ter-

minal strip (NS). A 5600 resistor (G12) to

inward

terminal of DC calibrate control (S), and to

pin #6 on 6SN7 socket (NS). A wire to inward terminal of AC

calibrate

control (S) and to pin

on

65N7

socket

(£}.

A

wire

to center terminal of ohms adjust control

(5)

and to

center ter-

minal of DC calibrate control (NS), A 12 MFD condenser (V27)

with

positive lead to lug on

selenium rectifier farthest from

chassis (S) and with negative lead to single terminal strip

(S).

Assemble battery bracket as shown and

mount on the chassis

with the triple terminal strip and a solder lug under the nut, A

black transformer

lead

to

lower

lug {nearest chassis) on ter-

minal strip (NS). A wire to pin #6 on

6HB

socket (S)

and

to

out-

side

terminal

of

AC balance control (S). A wire to pin

#3

(NS)

on GH& socket and, to

middle

lug

on

terminal

strip (NS). A

.01-

l,00Ov condenser

(024)

toe enter terminal of AC balance control

(NS) and

through

solder

lug

{$)

to

battery bracket terminal

nearest roar edge of chassis

(3).

Two 1 meg resistors

(Ol7)

to

center terminal

of AC balance control (S), one to middle lug

(S) and other to upper lug (ft

5)

on

terminal

strip.

r.".P

On the

panel

(V 51

C),

mount the

pilot light assembly

(039,

O40,

041,

042,

052)

with the

bracket

toward the slide switch opening. Mount the

slide

switch

(034)

with

6-32

screws and nuts.

Mount

the

banana jacks with speedmits

(044),

the blackjack (V77B) in the hole

marked common

and the red jack (V77R) in the hole marked AC

Ohms.

Push the

banana

jack inserts (M28) into

the

jacks

from,

the

front

of

the panel as far as they will go. Mount the phone jack (K17) with

a control nut using a control Lockwasher between jack and

panel

and

a nickel washer between

panel

and nut. Mount the range switch (V75) to the panel with a

control

nut, using a

lock

washer

between switch and panel and a

nickel washer between panel

and

nut. Tighten nut partly. Tem-

porarily install a pointer knob.

Turn

switch

counterclockwise

as far

as it will go. Kow turn

the whole switch so the knob points at 3V

-

Rxl. Carefully remove knob and tighten nut,

...

,

)

Q£f~fltL

OFBAttAWA

JACK.

how

TO

mount catirfiai.5

i

stvj

Tt/tES

Wire the range switch by mounting the multiplier resistors (V103, V73, V74, V6B,, V66, V65,

V71, V7Z and V70) as shown in the pictorials

Note

that

the

30K

resistor

(V66)

connects

to

the grounded

lug on

the

phone jack. The 8.3 resistor (VI

03)

is soldered to the

switch without

shortening the lead, after

slipping

on

a

piece

of spaghetti. The other side v=

connected later.

Page

%

G=fiJ

9

,

In stall

the

selector

switch (V2 8

A

)

with a c

ontrol

mit

,

using a c ontrol

locfcwash

er

between switch

and

panel and a nickel

washer

between nut and panel.

Make

sure this switch ts

mounted

as

shown

in the pictorial. A

bare

wife

to black banana jack

(SJ

and

to ground

Lug on phone

Jack

(B).

A bare

wire

to one lug on pilot light (S)

and

to pilot light bracket (S),

10.

A wire

ta front outside lug on

range

switch (S) and to lug W3 oh

front

deck

of selector switch

(5).

A wire to lug

on range switch to which 7 meg

resistor

is connected

(3)

and to lug

#9

on

front deck {nearest

panel)

ol selector switch (S). A wire to

front

inside lug on range

switch

(S) and to lug

#1

on front deck of selector

switch

{$}- A bare wire to insulated

Contact

on phone

jack

(St

and to lug

#10

on front deck of selector

switch-

A wire to red banana jack (S)

and.

to

lug

#5

on front deck ol selector

switch

(3),

11.

Mount

the

meter (V4SC) on the panel

with

the

hardware

provided on the meter.

Loosen

the

nuts on the aero adjust and

ohms

adjust controls on the c hass i a . Slip

the

panel oyer the bushings'

of

these

Controls and replace the nula using

*

nickel

washer between nut and panel. A wire

to pin

#7

on 6SN?

socket (S) and to lug on pilot light aockai

(5)

A wire to lug #8 on front deck

of selector switch (S) and to upper lug

on triple terminal strip (S). A wire

to

lug

#8

on rear

deck

(farthest

from panel) of selector switch (S)

and

to nearest terminal of ohm s adjust control

(S), A wire to lug

#1

on rear deck of selector switch (S) and

to center

terminal of DC calibrate

control

(3).

A bare wire

to

lug

#6

on rear deck of selector switch (S)

and tu

pin

*3

on 6SN7

socket (S).

A wire to lug

#5

on rear deck of se lector

switch

f$)

and to center terminal of AC

calibrate control

($).

Slip spaghetti over the lead on the 8.3 resistor

from the range switch

^nd

connect

to nearest lug of battery bracket (S).

12.

A

3.3

meg resistor

(010}

with

spaghetti

Over both leads to lug #2 on front

deck

of

selector

switch (S) and

to

pin

#4

on 6SN7 socket (S). A .01 MFD>2

,000V

condenser

<V79) with spaghetti

over

both leads to lug

*4

on

Jront

deck

of selector switch (S) and to pin 03 on

0H6 socket

(SJ

r

A wire

to

lug

on rear deck of selector switch

fS)

and through

nearest grommet In chassis

to meter terminal

nearest

AC balance control

^3).

A

wire

to lug #4

on rear deck of selector

switch

(S) and through nearest prom

met

in

chassis

to meter terminal nearest tube sockets

($).

The

remaining

black transformer lead to upper lug

on slide switch (S). Place the line cord

(078)

through the

grommet

in

the rear of the chassis. Tie a knot for strain

relief

and one

lead

to lower lug on slide switch (S),

other

lead to lower lug on triple terminal strip (S).

A

wire between

the top lugs on the battery bracket (S),

13. Make

up

the test leads: The common

lead is

black test lead with a black

banana plug

(V39) on one

end

and an alligator clip (V44) on the other

end-

The AC ohms lead is red test

lead {V46) with a red

banana plug

(V4Q) on one end and a red test prod (V42) on the

other

end.

The DC

lead

is

shielded

test lead (V47) with a phone plug (V41) on

one

end

and a small I meg

resistor (V56) inside the black

test

prod (Y43), Prepare the cabinet

(V53)

by Installing

the

handle

(079)

with

1

0-24

screws and by pushing the rubber feet

(034)

into

the holes

in the bottom.

Install the acorn knobs

[V4%]

on the adjust controls, and the pointer

knobs

(051) on the

switches.

//VSrAi.1

FFfr

AS Sffl)W^

PHOVG

PLUG

AWM&LY

Page 3

TEST AND CALIBRATION

Chock the

wiring over carefully. We suggest tracing over each wire on

the

pictorial with

a colored

pencil a a it is checked on the

instrument.

Check each solder connection. Install the

tubes.

Pluu

into a )17

Volt

50/60

Cycle AC ONLY outlet. This

Instrument

will not

operate

and

serious

damage will result if connected to DC-

Turn switch on and allow a

minute for

warm

up. Set selector to DC +. Check operation ol sero

adjust Control-

Turning this

control should move the meter pointer to about

half

scale and

to

auro.

Set jioinlerto zero

andchecluf it

remains

on iero when switched to DC

-,

If there is appreciable

zero shift (more than one division on the stale) the

tubes

must

beaded.

First complete the initial

iest

r

however.

Insert

the

common and DC test leads. Set the selector switch to DC

+

and

the

range

switch to 3v.

Connect the calibrated flashlight cell and adjust

the DC

calibrate control so the meter pointer

indicates the

calibration

voltage

on the 3V scale.

Install the

batteries

in

the

battery bracket as shown. Set selector

switch to ohms. Pointer

should

swin^ to about full stale. Turn, ohms

adjust to pive full scale reading (IN Finite). Insert AC ohms test

lead.

Touch

th.i*

loud

to common lead and observe pointer dropping to zero

indie at I oil .short circuit (no resistance).

Temporarily remove AC ohms test lead. Set

range

switch

to 3V and

selector

to AC.

Adjust AC balance control so no movement is noticed

in

the pointer

when .switching from AC through DC

-

to DC

+,

Now set

range switch to 300V, Re -insert AC ohms

lead.

Connect

AC ohms and

common lead lathe 117V AC line [NOTE: 117 Volt line is dangerous-

-

proceed with due care) and adjust AC

calibrate

control so pointer indicates the line voltage.

It is recommended that the

tubes be aged

before final calibration. This is accomplished by keeping

the

instrument tumtd on for a period of at least 48 hours.

Final

calibration should

be

done

in

the same way as the initial calibration. Careful calibration will result in a

more

accurate in-

si rum cut , Ha standard AC meter is available,

it is desirable to use such instrument, preferably

at

a

voltuge near full scale indication on the VTVM, as for instance 250 Volt or 90 Volt {on the

300V or 100V

scale respectively).

After

final calibration, install the instrument in

the

cabinet with sheet metal screws through the

panel and in

the rear

into the chassis. This completes the

instrument.

CIRCUIT

DESCRIPTION

This

instrument uses a balancedvacuum

tube

circuit to increase the sensitivity and provide greater

flexibility. The relationship

between

the

test

voltage applied to the tube and the indicating

meter

current is

linear over a range appreciably

greater than

the

operating range, When a much larger

teat voltage is accidentally

applied

h

the

relationship ceases to be linear and

the

indicating meter

current is

limited

to a value of a few times full

scale

current. This makes

the

meter, when used

in. this circuit, virtually

burn

out proof. Repeated overloads should be

avoided,

however,

as the

pointer may

be bent.

The

zero adjust control balances the

currents

through the tubes and permits the meter to be set

to aero, or

partly

up scale.

The

calibration controls are in series with

the

meter and

are adjusted to produce full scale reading

wLUi the proper test

voltage

applied to the instrument.

The

maximum test voltage applied to the

tube is about 3 Volts, Higher test

voltages

are

reduced by a voltage

divider

with a total resistance

of 10 megohms.

An additional resistor of 1 megohm is located

in

the

DC

test prod, which permits

measurements to be made in

circuits carrying K, F. with minimum

disturbance

of

such

circuits.

Pafje

4

For AC voltages in

the

Audio Frequency

range, a shunt fed diode is used to provide

a

DC

vyltage

proportional

to the peak of the applied AC voltage. This DC voltage is applied

through

the voltage

divider to the tube, causing the

meter

to indicate*

The

AC calibrate control is used to

get

the

proper meter

deflection

the applied AC voltage r Vacuum tubes develop a contact potential

voltage between tube elements, Such contact potential developed in

the

diode

would

cause a slight

voltage to be present

at all ti meg-

This voltage

is cancelled out by bucking it with a.

portion

of

the contact potential of a second diode. The amount of bucking

voltage

is

controlled by the AC

balance control. This

eliminates

zero

shift when

switching from DC to AC.

For resistance measurements, a

3 Volt

battery ig

connected

through a string of multipliers to

the tube.

The external

resistance

to be tested is connected between tube and common {chassis),

forming, 'together with

the

multipliera, a voltage divider

across the

battery- The resultant portion

of the battery

voltage

is thus nop I led to the tube causing the meter to deflect. The meter

scale

i&

calibrated in resistance.

The operating

power

for the lube is

obtained

from a power supply uging a power transformer, a

halt

wave

selenium

rectifier, a filter condenser and a voltage divider,

The VTVM has many advantages over

the

non-

electronic

volt-ohm meters- The greatest advan-

tage is the high input resistance. This ejiables much more accurate readings to be obtained in

high

impedance circuits,

such

as resistance coupled amplifier^

oscillator

grid circuits and AVC net-

works.

To illustrate this, let us assume

a

resistance Cfupled

audia amplifier

with

a

-5

megohm plate load

resistor operating with a 100 Volt plate supply, Let us also assume that the plate voltage

is

50 Volts and that, therefore, the tube acts as a .5

megohm resistor.

Measuring

the

plate voltage

with a conventional

1,0(30

ohm per volt instrument on the 100 Volt scale, the meter can

bo

con-

sidered a

100,000

ohm (A megohm) resistor in

parallel with

the

tube.

The voltage on the plate

is then about H Volts and is shown as such by the meter. This is due to the shunt resistance of

the low resistance meter,

Using the

VTVM

pn any

scale

getting

>

the full 11 megohm is placed in

parallel with the tube, The voltage on the plate is then about 43 Volts or

2%

lower than the nor-

mal operating voltage. Thus accurate reading can only be obtained with

the high

resistance pro-

vided by

a VTVM,

Similar benefits are obtained in AVC, oscillator and other

high

resistance

circuits.

An

understanding

of the

Characteristics

of your instrument will result In

greater

satisfaction

through proper use-

UStNG THE VTVM

Page 5