Hughes MCW-550 User manual

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 



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P,

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  :

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>,: )  7

  

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 



Warrant~

Applicable

to

Production

Equipment

sold

by

the

Industrial

Products

Division

of

Hughes Aircraft Company

1.

Except

as

may

be

otherwise provided

in

paragraphs 2 and 4 below;

any

production

equipment

or

parts

thereof

returned

within.one

year

from

the

date

of

its shipment

'and

found

by

Hughes

to

be

defective

in

material

or

workmanship, will be repaired

or

replaced free

of

charani. However, where

Purchaser prefers

to

effect

repairs

and

replacements.

at

its

own

expense

and

risk, a credit

or

replacement will be issued for

any

~art

for

which

Pur-

chaser

at

its expense·has obtained a replacement from Hughes, provided

that

said

part

is

found

by

Hughes to

be

defective

in

material

or

workman•

ship

and

is

returned

withm one

yeat

from

the

date

of

shipment

Qf

the

equipment

into

which

it

was incorporated.

Such

credit

shall be

at

the price

charged Purchaser

for

the

replacement part. Unless Purchaser requests a credit

at

t.he time

it

returns

the

part, a replacement

p~t

rather

than

a

credit

w~

be issued. ·

2.

Repair workmanship performed

and

parts repaired

Qr

replaced

free

9f

charge

by

Hughes are warranted against defective material and work.ma&

ship.

To

qualify for .such warranty·

the

repaired

or

replaced

equipment

or

part

must

be

returned

to

Hughes either within

the

ninety

day

period

immediately following

date

of

shipment

or

within

the

remainder

of

the

one

year

warranty period

on

the

original

equipment.

whichever period is

longer,

and

must be found

by

Hughes

to

be

so defective.

3. Estimated .repair and replacement c.harges will

be

submitted

to

Purchaser

for

equipment

or

parts

thereof

not

covered

by

any

warranty

set .forth

herein. Upori receipt

of

Purc;haser's apptoval thereof, necessary repair

and

replacement

work will

be

promptly

accomplished. ·

4~

'Repair and repl~dernent work performed

by

Hughes

at

Purch~r•s

expense;and

parts sold separately from

the

equipment

for

which

they

an, a

ce>mponent are wa:qanted

for

a

period

of

ninety days

from

the

date

of

shipment

to

be free

from

defects

inmaterial

and workmanship,

and

will

be

repaired

or

replaced

fr~

of

charge when

the

item

repaired

and/or

replaced

or

the

part

sold

is

returned

within

the

warranty period

and

is found

by

ijughes

to

be

so

defective. . .

S.

Where repair, replacement

or

credit is

not

allowed for

any

returned

equipment

or

part,

and

approval

of

repair

and

replacement

work

is not

re-

ceived within sixty days from·

the

date

estimated

charges therefore

.p-e

submitted, such

equipment

or

part

will

be

returned

to

Purchaser

11.t

its

expense plus a handling

and

inspection charge

of

five percent

of

the price

of

such item.

6.

Equipment

or

parts which have been subjected.

to

accident, alteration, misuse, abuse, tampering

or

operation

other

than

as specified

and

printe<l,

are

not

covered by.the

w~nmties

specififd above and no repair, replacement

or

credit

will be allowed with

respect

thereto.

. .

7. Subject

to

the

provisi<>n

of

the

''Patentlm;ternpity"

clause

of

its Sales

Tenns

and

Conditions, Hughes also warrants

that

it

has

the

dght

to

sellits

production

equipment

and

parts

theteof,

that

Purchaser shallhave

and

enjoy

quiet

possession

of

such

equipment

and

parts as against

any

lawful claims

existing thereagainst

at

the time. of

the

sale, repair

or

replacement

thereof

by Hughes,

ana

tliat

said ~quipment

and

parts

at

the

time

ofsale,

repair

or

replacement

by

Hughes are free

from

any

charge

or

encumbrance

in

favot

of

any

third

person.

8. The warranties set forth herein

are

restricted

to

the

original Purchaser.

The

foregoing constitutes Hughes'

entire

warranty,express,

implied

or

statutory,

with respect

to

its

production

equipment,

parts

thereof

or

ther.efor,

and

repair thereof,

and

states

the

full

extent

of

Hughes• liabilities

for

breach

of

warranty

and

for

damages, whether direct, special

or

consequential; resulting

from

any

such breach. No change

whatsoever

10

such

war

..

ranties shall

be.

binding

upon

Hughes unless in writing and signed

by

a

duly

authorized Hughes• representative.

EXCEPTION:

Electrodes and heater thermocouple cartridges (expendible items) are warranted against defective material

and

workmanship

for

a period

of

30

days immediately following date

of

shipment.

( (

NOTES

( (

( I (

( (

HUGHES

OPERATION

AND

MAINTENANCE

MANUAL

HUGHES

MODEL

MCW-550

CONSTANT

VOLTAGE

WELDING

POWER

SUPPLY

SERIAL

NO._

___

_

Revision

No.

2 July, 1972

TABLE

OF

CONTENTS

SECTION

PAGE

1.

Description

.............................

,

.......................

:'

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2.

Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..

. . . . . . . . . . . . . . . . . . . . . . . . 3

3.

Electrical & Mechanical Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

4.

Maintenance, Calibration & Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

5.

Duty Cycle Capabilities

...........................................................................

9

6.

Schematic & Parts List

........................................................................

10-15

Schematic

diagrams

&

Parts

list

in

this

book

apply to all

MCW-550 units Serial No. 266 andup. Consult factoryfor

schematic

diagrams

pertaining to

earlier

model units.

SYMBOL

DESCRIPTION HACPARTNO.

( RY1 Relay, Power, DPDT 10 AMP,

115

VAC

Coil 580HO44

( RY2 Relay, Power, DPDT 5

AMP,

115

VAC

Coil 580H027

S1

Switch, Power, DPST, 15A-125V 720H001

S2 Switch, Power, DPST, 15A-125V 720H001

83A•s3B•s3C Switch, Thumbwheel (voltage) 720H059

S4A,84B,8

4C

Switch, Thumbwheel (duration) 720H060

T1 Transformer, Power{F90X) 750H074

T2,T3 Transformer, Power (RT-204) 750H073

The Hughes Model

MCW-550

Constant Voltage Welding Power Supply

Fan Muffin, Venturi 260H001

SECTION I The

DC

pulse is obtained from

an

electro-chemical source Bat. Nickel Cadmium Cells (4) 118H001 (4)

(nickel cadmium cells) providing a pure

DC

source that is

DESCRIPTION -MCW-550 unaffected by

AC

line fluctuations or transients.

CR

1 Diode IN60 560H027

The

MCW-550

Power Supply

is

an all solid state

CON-

Wide

Range Timing Control with Three Range Selection

on

CR2.12 Rectifier 1

AMP

200V 560H010

STANT VOLTAGE Power Supply designed specifically Digital Dial Control -Timing control is effected with three

for parallel-gap (series) welding

of

integrated circuit pack- digital tlmmbwheel dial controls on the front panel. Three CR13.J6 Rectifier

15

AMP

5

0V

560H029

age

leads to printed circuit boards, and fine ribbons & ranges are covered from 1 • 99, 10 • 990, and 100-9900

wires to thin films.

It

may also

be

used for conventional milliseconds.

opposed-electrode resistance welding

of

virtually any type ( (

SCR

1 Silicon Rectifier 2N1842 560H025

of

small assembly.

Weld

timing settings are easily and accurately adjusted

by

aninexperienced operator. Q1,Qz,Qs,Q7,Qg, Transistor 2N1193 560H020

Automatic Recharge

of

Battery Supply -An automatic

Q9,Q11,Q23,Q24

DESIGN FEATURES charger

is

incorporated to maintain the battery voltage

Q3

Transistor, Unijunction 2Nl671A 560H071

within very close tolerances at all times.

Constant Voltage Output -The

MCW-550

provides a Q4,Q6,QlO Transistor 2N1990 560H022

constant voltage output (as preset on the digital dials) Under standby conditions, the automatic charger will Q12,Q13,O25 Transistor 2N2137 560H023

which assures uniformity

of

welding results over a broad maintain the battery within plus or minus .10 volt

of

a

range

of

variables in materials, thickness, cleanliness and nominal value. Under welding conditions, the charger will Q14-21 Transistor Power (Special) 560H018

electrode tip variations. turn on upon demand after each weld when operating

at

Q22 Transistor 2N251 560H021

high discharge levels.

The power supply delivers a varying current output that Q26 Transistor 2N2156 560H031

automatically compensates during the welding cycle for Under most circumstances, the energy removed from the

variations in resistance occurring in or across the weldment battery after each weld is replaced within one second.

and will

at

all times (within the current range

of

the power (See duty cycle table for complete capabilities

of

system.)

supply) maintain the constant voltage that has been preset

VR

1 Zener Diode 1N1591A 560H026

on

the digital dial. The constant voltage will assure that Completely Solid State -All control and power circuitry

the current density remains constant during the weld

cyi::le.

is

solid state. No warm up time

is

needed. Timing and

VR

2 Zener Diode 1N1779 560H028

power output from the beginning to the end

of

a pro-

VR

3 Zener Diode

1N4733

560Hl15

The power supply's ability to compensate for load changes duction work day will

be

uniform.

\l

VR

4 Zener Diode 1N1593A 560H030

is

nearly instantaneous and can be assumed to be faster

than one hundred micro-seconds in most cases. Illuminator Lamp Power Integral - A power supply and

power switch is incorporated in the front panel with out-

The constant voltage output will remain regulated within let receptacle

to

operate a standard Nicholas illuminator.

twenty-five millivolts throughout the range

of

dial adjust- FOR 230 VOLT MODELS ONLY

ment. Vacuum Port Outlets -The front panel incorporates a

power switch and has outlet ports for vacuum hose (

i'

T4

Transformer, 230V; 115V Stepdown 750H064

Uniform Square

Wave

-Pure

DC

Pulse Output -At all out- connections. This switch is marked Auxiliary

on

the front \

put levels from minimum to maximum a uniform square panel and may be used for other purposes. 50 -60 cycles 100 watts (Allied 62G557)

wave

.pulse

is

obtained that

is

easy to observe and readily

comparable from time

to

time for purposes

of

calibration Auxiliary Receptacles -

115

volt

AC

duplex receptacle

is

or quality control

of

the power supply equipment. provided at rear

of

chassis for convenience outlet.

F4

Fuse, 1

AMP

-

AGC

310H027

2

15

SYMBOL

R27

R29A

R29B(9)

R29c(9)

RTB(9)

RTA(9)

R33

R39

R40,R41

R43

R44

R45

R47,R42

R48

C1,C2,C3,C4,

c6,c7

C5

Cg

C9

Crn,C11

C12

C13

C14

CT1

CT2

CT3

,cT

4

,cT

5,

CT

6

,CT

7

F1,F2

F3

DESCRIPTION

Resistor, Fixed, Composition

Resistor, Fixed, Metal Film

Resistor, Fixed, Composition

Resistor, Fixed, Wire-Wound

Resistor, Fixed, Composition

Resistor, Fixed, Wire-Wound

Resistor, Fixed, Composition

Potentiometer, Wire-Wound

Potentiometer, 15 Turn Wire-Wound

Resistor, Fixed, Composition

Resistor, Fixed, Wire-Wound

Capacitor, Tubular, Mylar

Capacitor, Disc Ceramic

Capacitor, Metalized Mylar

Capacitor, Tubular, Electrolytic

Capacitor, Tubular, Mylar

Fuse, I

AMP

-

AGC

Fuse, 2

AMP

-AGC

Pilot Lamp, NEON

Receptacle, 4 Pin, Male

Receptacle, 4 Pin, Female

Output

Receptacles

Power Outlet and Receptacle

HACPARTNO.

590H182

590Hl84

5908195

590H199

590H197

590Hl98

590H201

590H159

590H160

590HI85

590H183

590H203

590Hl78

520H027

520H029

520H028

520H073

590H205

200H0S3

200H054

200H057

200H056

200H058

200H059

200H060

200H061

200H012

200H026

200H028

310H027

310H029

420H017

550H020

550H002

WO

2042

SS0H021

VALUE

300OHM

lK

lO0OHM

IOOHM

IOK

100K

1/2W

5%

1/2W

1%

1/4W

1%

1/8W

5%

l/4W

1%

1/4W

1%

I.SK lW

5%

l0OHM

5W

lOHM

2.2K

560OHM

3.0OHM

47OHM

150

OHM

300OHM

lK

200OHM

lO0OHM

25OHM

.01 MFD

.001 MFD

2MFD

1 MFD

250MFD

S0MFD

l00MFD

20KMFD

.1

MFD

IMFD

2MFD

SW

1/2W

5%

1/2W

5%

IOW

1/2W

5%

1/2W

5%

SW

1/2W

l/2W

2W

5%

SW

50V

±10%

SOOY

±10%

100V

10%

100V

10%

12V

SOY

25V

100V

10%

lO0V

10%

lO0V

10%

(

\ (

( (

SECTION

II

OPERATION-

MCW-550

CONTROLS

Optimum welding results can be obtained by varying weld

duration and electrode force and gap settings. Further

refinements can be made by adjusting the third voltage

>1 control thumbwheel for variations from .01 volts and

~

up.

Operation

of

the Model

MCW~SS0

.Constant Voltage

\V)\

Welding Power Supply is extremely simple

..

There are

o.nly

\;S

~

NOTE

two adjustable controls,

Weld

Voltage and Weld Duration.

~

\.~

The power supply makes

no

audible sound when

discharged.*

At

lower power levels, little or

no

effect will be noticed upon the materials being

welded.

In

addition

to

the main power switch, there is also an

Illuminator lamp switch and an auxiliary power switch

(connected

if

·a

vacuum pump is incorporated within the

power supply

or

other accessories).

An

external vacuum

pump may be connected

to

the front panel power switch

with hose take

off

thru the front panel ports

if

no integral

pump is installed.

CONNECTION

Prior

to

first energizing the power supply, connect the

weld head

to

the front panel receptacle with either cables

or

gold-plated copper bus bars

as

supplied for Hughes weld

heads. When using Hughes Model VTA-66 weld head,

connect 4 pin plug from head

to

the "Voltage-Fire"

receptacle·.

If

other Hughes welding heads having 2 pin plugs (such

as

Model VTA-60, VTA-62, VTA-64, or VTA-66-MA) are used

with this equipment, some provision must be made

to

connect the actuator firing circuit and the voltage feedback

circuit

to

the Voltage-Fire receptacle.

WARNING -SPECIAL NOTE:

IT IS IMPERATIVE

that

the feedback voltage wires

connecting· from the weldhead electrodes

to

pins in

the plug going

to

the Voltage-Fire receptacle be

connected with the proper polarity.

WHICHEVER ELECTRODE IS POSITIVE MUST

BE

CONNECTED TO PIN 1 in the plug

to

the Voltage-

Fire receptacle. THE NEGATIVE ELECTRODE

MUST

BE

CONNECTED WITH A FEEDBACK

WIRE TO PIN 2 in the Voltage-Fire plug.

With dual head systems,

b&

sure

to

observe polarity

marking on cables which will have RED dots indi-

cating the positive cable. The corresponding posi-

tive terminal

on

a VTA-66 or VTA-90 weld head

will also have a RED

dot

on

the end

of

the positive

stud.

DO

NOT ATTEMPT

TO

OPERATE THIS POWER

SUPPLY WITHOUT THE VOLTAGE FEEDBACK

WIRES BEING PROPERLY CONNECTED FROM

THE WELDING ELECTRODES TO THE FRONT

PANEL "VOLTAGE-FIRE" RECEPTACLE.

TYPICAL

OPERATION

Set

"Weld Voltage" thumbwheels

to

approximately

.30

volts.

Set

"Weld Duration"

to

S milliseconds.

If

a

VTA-66

wdd

head is being used, set

for

4 lbs. pressure

and electrode gap

of

.020". Test welds should be made

starting from these settings. Using the middle thumb-

wheel

of

the voltage control, increase settings in incre-

ments

of

.10 volts until some visible welding results occur.

DO

NOT OVERPRESSURE the electrodes in an attempt

to

"fire"

the welder.

Increase voltage and/

or

time in small increments between

test welds until satisfactory results are observed.

CAUTION The MCW-550 power supply will deliver

current

to

the limit

of

its ability in order

to

produce· the preset voltage. Since this

current may exceed 800 amperes, extreme

care must be taken to prevent the electrode

gap from shorting. Damage

to

the

elec-

trodes will be immediate

if

the power supply

discharges with the electrode gap set

at

zero.

Avoid setting the weld voltage to a high level and long

weld durations

at

the same time. Weld voltage settings

of

over ONE VOLT combined with weld duration settings

greater than 100 milliseconds will produce extreme heat

at

the electrodes.

Most microcircuit welding applications will be within the

range

of

.SO

-.85 volts setting and 5 -15 milliseconds weld

duration, or .20 -.50 volts

at

50

-

350

ms duration.

DO NOT EXCEED A VOLTAGE SETTING OF

.50

VOLTS

IN

COMBINATION WITH TIME DURATIONS BETWEEN

250

-500

MS

FOR

NORMAL WELDING.

NEVER discharge power supply with very low resistance

material beneath electrodes, such as heavy copper, brass

or steel plates.

* Sonalert audible indicator available from factory

in-

stalled in original equipment on order or also

avail-

able

as

field

mod

kit.

SECTION Ill

ELECTRICAL &

MECHANICAL

SPECIFICATIONS

MCW""""550

TYPE

OF POWER SUPPLY:

Constant voltage -direct current -square wave output.

WELDING PULSE CONTROLLED RANGE:

Time Duration: Adjustable from I -

9900

milliseconds in

three ranges.

Low Range: 1 -

99

milliseconds

Middle Range: 10 -990 milliseconds

3

High Range:

100

-

9900

milliseconds

Voltage Amplitude: Adjustable from .01-1.99 volts.*

*Maximum controlled voltage range

is

limited to load

conditions. With 2 milliohm load,

maximum

voltage

may

not

exceed,

1.30

volts.

CONSTANT VOLTAGE REGULATION:

Will

remain within 25 millivolts throughout adjustable

range.

MAXIMUM WELD CYCLE POWER:

Operating into a 2 milliohm load, maximum watts per weld

cycle will be approximately 850.

INPUT POWER REQUIREMENTS:

105-125 volts

AC

single phase, 50-60 cycle.

Average power in standby is 75 watts.

Maximum power-line. demands will

not

exceed 3 amperes.

MECHANICAL SPECIFICATIONS:

Weight: 65 lbs.

net

Height: 10-1/2"

Width:

20"

Depth: 13"

VENTILATION:

Forced air -Muffin fan

SECTION

IV

MAINTENANCE

-MCW-550

Batteries: The electrochemical battery source consisting

of

four nickel cadmium cells, is

the

only· component in

the

power supply

that

requires occasional inspection.

These cells, when originally installed

at

the factory, have

a preconditioning charge and the liquid level has been set

to

approximately

the

top

of

the plate separators(observed

when the power supply has been OFF for a period

not

less

than

eight hours).

Under normal microcircuit welding conditions, this battery

should require a minimum

of

care.

If

the

power supply is operated

at

higher

pow/r

levels and

near maximum duty cycle capabilities, then

it

is

possible

that

the

cells will occasionally vent moisture and over a

period

of

several months

they

may require the addition

of

small quantities

of

distilled water. Holes in the side

of

the

battery retainer allow observation

of

the liquid

level within the cell.

The

cells have a considerable latitude

of

electrolyte level. Water need

not

be added unless

the

liquid level falls be)ow the visible area

of

inspection in

the upper inspection hole.

See pages 9, 10 and

11

for detailed instructions

on

battery

care.

SPECIAL NOTE

When adding water, ALWAYS USE DISTILLED

4

WATER. Also, use extreme care when removing

the

vent

plugs in

the

top

of

the cells. These

pressure vent plugs are set

to

relieve

at

approxi-

mately 2

to

8 lbs. pressure, under normal operating

conditions.

To

add water, these vent plugs rotate

("

counter-clockwise approximately l/4

tum.

It

usually

requires a pair

of

pliers

to

loosen these vents. USE

EXTREME CAUTION

not

to

short the cell terminals

with the pliers. Preferably use insulated pliers.

Automatic Charger:

The

battery will normally be main-

tained at

the

correct degree

of

charge

by

an

automatic

system

that

senses the battery voltage and holds this

voltage Within very close tolerances. When the equipment

is turned off, the battery should read

5.0

volts total

or

1.25 volts per cell. Under operating conditions,

the

battery will read approximately

5.80

volts maximum with

a minimum near

5.

70

volts.

Additional Nates: A white powder residue may form

around the inside

of

the vent caps. This

is

a result

of

the

natural venting action and

is

normal

to

the operation

of

the cells.

The

cells contain

NO

ACID

and

DO NOT

give

off

noxious gasses

or

corrosive fumes.

Calibration

of

WELD VOLTAGE

The weld voltage circuit

is

normally calibrated at

the

fac-

tory

and under most conditions should remain constant

for the life

of

the equipment.

If

some components

on

the printed circuit board have been

changed during service or

if

it

is

desired

to

check this vol-

tage, proceed

as

follows: (

1.

Set WELD VOLTAGE thumbwheels to .10 volts

output.

2. Set WELD DURATION

to

a suitable time for making

asample weld.

3. Connect a storage oscilloscope across

the

welding

electrodes.

4. Perform a typical weld and observe voltage across

electrodes.

WELD VOLTAGE should

be

.10 volts.

If

not,

adjust

R28, which is

the

Left Hand

200

ohm

trim

pot

when

observing the circuit board from the component

side.

5.

SET WELD VOLTAGE

to

1.0 volts and repeat above

procedure observing weld voltage across the elec-

trodes.

If

weld voltage is

not

1.0 volts, adjust the

1000 ohm trim

pot,

R26, which

is

the Right

Hand

trim

pot

on

the

circuit board.

6.

If

either

of

the high or low

trim

pots were changed,

it

may be necessary

to

go

back and repeat the pro-

cedure with each trim

pot

again since there is a

small

amount

of

interaction between

the

pots.

CONSTANT VOLTAGE CHECK

After the above weld voltage has been checked or adjusted

and while still observing

the

weld voltage

at

the electrodes,

make a typical weld

on

some commonly welded materials

at

a fixed voltage setting. Then make several re-welds

or

insert additional thickness

of

materials.

The

voltage

at

the

electrodes will remain constant.

(

~·

,1

(

SYMBOL

R2

R3

R4,R5

R6

R7,R17,R20,

,R21,R22

Rs

R9

R10

R11,R31

R13

R14,R15

R16,R35,R36

R18

R23,R37,R46,

(

R50

R24

R25,R30,R32,

R34

+22V

-------------------------------------+22V

...------------------COMMON

f/1

r----------il'

-10VUN-REG.

,---..,_

__

......,R_49---+®

300.0. CHARGE CUT-OFF

CAL.

5W

WO

2091

SCHEMATIC MCW-550

DESCRIPTION

HACPARTNO.

Resistor, Fixed, Composition

590Hl76

Resistor, Fixed, Composition

5908181

Resistor, Fixed, Composition

5908191

Resistor, Fixed, Composition

590Hl92

Resistor, Fixed, Composition 590H188

Resistor, Fixed, Composition

590Hl94

Resistor, Fixed, Composition

590Hl93

Resistor,

Fi

xed, Composition 590H186

Resistor, Fixed, Composition 590H202

Resistor, Fixed, Metal Film 590H196

Resistor, Fixed,Composition

5908189

Resistor,

Fixed,

Composition 590H184

Resistor, Fixed, Composition 590H204

Resistor, Fixed, Composition

590Hl80

Resistor, Fixed, Composition

590Hl87

Resistor, Fixed, Composition

5908195

I

-10V

UN-REG.

-------r--4;~®

RV

1

T

T BAT.

T

VALUE

5.6OHM 1/2W

270OHM

l/2W

47K 1/2W

100K I/2W

lOK 1/2W

22K 1/2W

510K 1/2W

4.7K 1/2W

2.7K lW

1K 1/4W

15K 1/2W

lK

1/2W

33K 1/2W

220OHM

1/2W

5.6K 1/2W

lO0OHM 1/4W

5%

1%

5%

13

12

+

22V

± 10¾

REGULATED

On

Tt

1A

F1

R9,1D

VR23j

CR11,

12

3

-6.8±10%

REGULATED

025

VR1

1A

F2

120V

00~1

fl'

--

0--

r

T

CHASSIS

GROUND

r'

--------------------

..,

I

!

I

03

I

PULSE

TIMER

I

L

PANEL

WELD

DURATION

TIMING

CAPACITORS

01

02

FLIPROP

CR1

r---

1

I

04

PULSE

TIMER

CUT-OFF

I

Qi;DG07

R26

R2&

MAX,V

MIN.V

I

AL.

CAL.

I

I I

_Jl.__

I I I

L-,

I I

ACCESSORY

I I I

ITEM

,----_...__

02

,._

7

_.__....,

SONALERT

FEEDBACK

PANEL

WELD

VOLTAGE

I

,---.jf---4-,

I

PRINTED

CIRCUIT

BOARD

as

010

I

(lg

v~~!~~E-

I

AMPLIFIER

I

_J

PANEL

ILLUMINATOR

RECPT

WO

2308

012

013

CURRENT

AMP,

BLACK

014

POWER

RI\/E

WELDHEAO

ACTUATOR

r-

-

2A

F3

VOLTAGE

REGULATED

BATTERY

CHARGER

.RY·l

~=!:~=~~!

PANEL

OUTPUT

TERMINALS

VOLTAGE

VR3

CALIBRATION

R49

MCW-550 BLOCK

DIAGRAM

Rs

100K

R7

Rs

lOK 22K

R22

10K

R9

R10

A11

610,K

4.7K

2.7K

1W

R23

CR4

220.Q.

SC2

R24

CR5

5.6K

SC2

,_

__

..,_~f------+=-1--~R-~-t--l--t---

B~E

--~

200

-------71

I I

11

Rzectel

I I

10n

7%1/llW

I I

BASE

07

S3e

COL.05

I I

EMITTER

03

06

2N1190

MIN.V

r

7CAL.

I

R25

R30

100n

¼W

JUNCTION

R2-R3

EMITTERI

03

I

R2l}

WELD

VOLTAGE

___

--1L

JUNCTION

R1-R12

RT

WELD

DURATION

- -

_J

NOTE;

1

ALL

CAPACITORS

DESIGNATED

IN

MICROFARAD$.

2

ALL

FIXED

RESISTORS¼

WATT

UNLESS

OTHERWISE

SPECIFlEO.

WO

2091

SCHEMATIC MCW-550

( (

\

( (

TIMING CALIBRATION -Normally fixed

at

factory.

If

the printed circuit board is replaced or

if

Q3

is

changed,

then CT1 and CT2 trimming capacitors will have

to

be

corrected.

To

obtain the most accurate timing, set

90

milliseconds on

the

LOW

range (.0) and trim

CTl

for

nearest value

to

90

MS.

Repeat process on middle range

(0) while set

at

900

MS

and trim CT2. The

output

of

the

MCW-550

unit

should be operating WITH NO LOAD

while making these timing adjustments. Scope observa-

tions may be made across the electrode tips with an

insulating

pad

beneath the tips

to

prevent current flow.

SERVICE

INFORMATION

-

NICKEL

CADMIUM

BATTERIES

The following information will be helpful in determining

the condition

of

an

MCW-550

battery and explain means

to

maintain the battery properly.

The liquid level

of

each cell,

as

observed through the

ports in the retainer case, is a reasonable indication

of

the

degree

of

charge only

if

you

know

what

the

past operating

conditions have been (the last 6 - 8 hours

of

operation)

and in some cases only after observing another 6 - 8 hour

period

of

operation.

FACTORY

CONDITIONING

The liquid level (electrolyte) is adjusted

at

the factory

to

approximately 1/

16"

over the

top

of

the plate separators

while the unit

is

turned

off

and only after

the

unit

has

been

off

for a period

of

12 hours or longer.

Prior

to

the 12

hour

OFF

period, the

unit

would have been

in operation for a period

of

time

that

was sufficient

to

com-

pletely charge

the

battery

to

the set level. (The set level is

5.

75

-5.80 volts, after unit has been ON one hour.)

DETERMINING DEGREE OF CHARGE

To determine

that

the

battery

is adequately charged

(for

units No. 131 and up) the MCW-550 should be turned

on

and

left

in a standby condition for approximately one

hour. After this period

of

time the

battery

should be

charged

to

the maximum level

as

previously set

at

the

factory (assuming

that

the

unit

had

not

just

previously

been subjected

to

an extremely high duty cycle

at

high

power levels).

The battery voltage should be between 5.75 and 5.80 volts

as

measured with either a digital voltmeter or a 1/4%

accurate meter. This voltage measurement is extremely

important • do

not

trust !. tyPical multimeter.

The

liquid

level after several hoursin standby or after operating should

be approximately

1/8"

to

3/8"

over the top

of

the

plate

separators.

It

is normal for the liquid level

to

rise during

operation and

to

fall back

to

plate level during

OFF

periods.

If,

after one

hour

of

standby time, the liquid level is still

at

plate level

or

below and

if

the battery voltage is still below

5.75

but

continuously rising slowly,

then

it

can be assumed

that

the battery was in a low state

of

charge when first·

turned on. The power supply should be left in the standby

condition until the battery voltage ,ceases to rise and be•

·comes steady

at

5.75 -5.80.

If

the battery voltage were

to

stop

at

some

point

below 5.75, a very slight clockwise

increase

of

R49

(pot

adjacent near positive

battery

cable

on

chassis) would bring

the

voltage up.

DO

NOT

USE A GROUNDED VACUUM TUBE VOLT-

METER WHILE MEASURING BATTERY VOLTAGE.

DETERMINING CHARGE OR NEED

FOR

WATER.

To

accurately set the liquid level (or

to

determine the need

for addition

of

water) the

battery

must be observed

AFTER

the unithas been

OFF

for a period

of

8-12 hours (following

the previous day or period when

you

know

that

the

unit

had been on for a period

of

time necessary

to

reach

the

maximum set charge level

of

5.75 -

5.80

volts).

The liquid level should be approximately

1/16"

over the

plate separators(all cells should be nearly the same).

If

the

liquid level is more

than

1/4"

below the

top

of

the plate

separators, additon

of

distilled water

is

needed.

If

the

liquid level

is

more than

1/4"

above the plate separators,

it

would be best

to

remove some electrolyte down

to

the

1/16"

over plate separator level

(to

minimize spitting)

al~

though this

is

not

necessary for satisfactory operation.

If

the liquid level is maintainedexcessively high, considerable

venting action will occur which will result in excessive

powdery residue around the vent plugs.

The use

of

plastic caps (supplied

by

the factory

upon

re-

quest if

not

already installed

on

unit) pressed down tightly

over the vent plugs will minimize the spreading

of

the

vented residue over the

top

of

the battery.

MCW-550 UNITS NOT IN USE

FOR

SEVERAL WEEKS

OR

MORE LIQUID LEVEL

In some cases in units which have

not

been operated for

several weeks or longer, the battery liquid level before turn

on

may

be

below the upper inspection

port

and still above

the lower

port

and

not

be visible.

If

this appears

to

be the

case, tilt

the

power supply

on

either side until

the

liquid

level can be observed.

If

this is the case and the level is be-

tween ports,

the

MCW-550 should be energized for several

hours in standby and observe

that

the liquid level rises

to

approximately the level

of

the plate separators.

In

most

cases

it

will return correctly. If, after several hours

of

operation, the liquid level does

not

come all

the

way

up,

turn

unit

OFF. Twelve hours or more later, preferably

the

to

bring level

up

to

just

over

plate separators

(1/

16").

UNITS -SERIAL NO. 101

~

130

All

previous information applies to these units (No. 101

through 130) except

that

the battery voltage is

not

fixed

at

5.75 volts. The battery charger cycles between 5.25

and

6.00 volts,

and

usually turns on only upon demand when

welds are being made.

To

check

that

battery

is

at

maximum charge or

to

bring

the battery

up

to

this

point,

the

MCW-55()

should be

operated

at

a low

duty

cycle and preferably

at

low power

settings. Under normal conditons, when the battery is

charged adequately, several welds can be made and

the

battery voltage will slowly fall with each weld.

At

a

5

voltage near 5.6 -5.7 volts, the charger

will

turn

on and

return the battery

to

approximately 5.95 volts.

This battery voltage will then taper

off

slowly until

sufficient energy has been withdrawn

to

reduce the battery

voltage

to

the 5.6 volt level and again the charger will

tum

on

automatically and repeat the charge cycle.

DETERMINING CHARGE STATE-SERIAL NO. 101-130

After operating

at

a low duty cycle for a period

of

one-half

to

one hour, and

if

the battery voltage has repetitively risen

to

5.85 -5.95 volts and fallen back

to

5.50 volts plus or

minus

1/4

volt,

it

can be assumed that the battery is

at

the

nominal charge level.

The level

of

the liquid should be

1/8"

to

3/8"

over the plate

separators during periods

of

operation. After

it

is known

that

the unit has operated for a period

of

several hours and

presumably reached a well charged condition, then twelve

hours later (or preferably the next day) before the unit

is

turned on, the liquid level should be ~pproximately

at

plate

separator level or up

to

1/8"

over.

If

the level were to be

considerably less than this

(1/4"

below plates

or

more)

distilled water should be added

to

bring the level up.

While monitoring the charge voltage cycle,

if

the maximum

charge voltag~ does

not

fall within the range

of

5.85 -5.95

volts, then adjust R49

pot

on chassis near positive cable

to

obtain this setting. ADJUST THIS POT VERY CARE-

FULLY. A very slight clockwise increase will increase the

charge voltage considerably.

ADDITIONAL NOTES

1.

When first inspecting a unit for battery condition,

always check

that

the fuse

F3

is good.

F3

should be

a 2 ampere rating and

on

some early units

it

may be

found

that

a 1 amp fuse has blown, allowing the

battery

to

run down.

2.

The charge rate

of

all units

is

approximately 4-6

amperes. Even

if

the battery were to

be

almost

de-

pleted, a period

of

5 hours in standby would return

a battery

to

almos{ full charge.

3. Under normal microcircuit welding conditions (flat-

packs at settings

of

.75 volts and 5-10 milliseconds)

or thin films

(at

.50 volts and

300

milliseconds), the

level

of

charge will always remain

at

maximum.

During operating

at

these typical weld settings

and

assuming a duty cycle

not

in excess

of

1800 welds

per hour,

the

charger will automatically replace amp

hours

of

energy at the same rate

that

it

is

consumed.

4.

If

a battery is known

to

be completely discharged, it

should be returned to the factory for a complete re-

charge conditioning cycle.

GENERAL TROUBLE SHOOTING

(

Symptom Most Probably Fault Area ( (

Double or multiple pulse

Power

at

electrodes with Welder Power

OFF

Power at Electrodes with Welder Power

ON

but

with

actuator OPEN. Minimal Voltage Control ·

Excessive Power

at

Electrodes during weld.

No

control

withWeld Voltage.

Power

at

electrodes with Welder Power

ON

and with

Actuator Open or Closed. Voltage Control operational.

Weld Pulse completes selected Weld Duration even though

actuator opened immediately after start

of

pulse.

Weld Duration continues beyond selected duration

as

long

as

Actuator held closed. Voltage control operational.

Contact bounce in actuator.

Replace micro-switch.

One or more

of

Power Transistors partially or completely

failed. Replace. See Note No.

1.

QB

and/or Q9 defective. Replace.

Q7 defective. Replace

Q5

defective. Replace

Q4 defective. Replace. Note: Q4 function

is

to terminate

pulse with release

of

actuator regardless

of

selected

Weld

duration. This serves

as

a degree

of

protection

of

work be-

tween the electrodes where through error an excessive

Weld Duration has been selected. Where this endpulse-with-

actuator feature

is

not

necessary or desired, Q4 can simply

be removed from its socket.

Q6, Q3,

or

Q2 defective or

not

seated properly in socket.

Check. ·Replace where necessary.

No

output

. Q2 defective. ·

__________________________

(

NOTE

1:

In

above symptoms the expression "Power at

Electrodes'_' is used

to

indicate a FAULT condi-

tion

as

the

mere presence

of

"Voltage"

at

the

electrodes

is

a normal condition.

6

In the power OFF condition and with a pro-

perly operating unit, a voltmeter placed across

the Welder Output terminals will indicate a vol-

tage

of

approximately 5 volts depending

to

(

SCR1

Cl:

0

...

~·

~

a s0

t)

t.O

f:l

..

Cl:

Jj

Ji

0 8

!,!

~

t«-1~

K 560Sl 1N1779

I -

--

L_

--

- -

_J

PART

OF

HEATSINKSUB•ASS'Y.#1

(TOP

VIEW)

Ill

~

Cl:

Ill

i >

!;l

;;i

!:.J

w

I'

HEAT SINK 8

..

§

0

<(

SUBASS'Y.

"2

(:}

--

s:~.11:~==-=--=--=--:..

........

-

..

~~JI,.._

___

___,

'--+-

....

-+--+--t--+--+-_...,,-+--6-4-4.-+----+

WELD

HEAD

.,__.,__....,__

_

__....

_

__,.

_

_,.,-.....----,1..,___...,_--+_

R41

I

TO

T1

~

PRIMARY

~

RY1

HEAT

SINK SV,B·ASS'Y.*2

_____

_,. NEG.BATTERY

~

i......-------POS.BATTERY

WD

2108

SCHEMATIC

DIAGRAM

-

HEAT

SINK

SUB-ASSEMBLIES

.

31

16 •

'

~,,.

R2e-2oon

I /

MIN.

V.CAL

@)+k, -

R10

CR6

,

sc2-._

4.7K

+22V

REG.

14 -

'

_h..,

R2

R4

A5

Ra

R7

Rs

Rg

R11

R31

_

RT

5.6.0.

47K

100K

10K

22K

510K

2,7K

-~

2.7K

13

1W 1W

CR11N~O

I

R24

CT

I

f--4;-

~2~

990

f"

R21

~

5.GK

' 12 -CR3

10K

,

CR7

I

Mi

R'3

18

SC2

~

270,1

C5

33K

2N1193

.,,,

CT/RT

"~

oz

:::

R22

R23

"~5

[d,,

.001

10K

220ll

C13,~

_ COMMON

#1

100

MAX.

~

10

[§Ii

iii

R13

~

2N1193

....

R31

1K n

CR~L

,~.,

~

196

R14-15K R15.JSK

SC2

~J

~·~

7

CR4

07

R33

ACTUATOR-~to-i

C5

2N1193

.01

SC2

;,.

1.5K

C3

.01

"

1W

ACTIJATOR-4 I-

--

CR5

7 R30

I

I~

SC2

,oon

,-

©,E+o

I

CR2

C7

R25

SC; A15 .01

R2Q

100n

1K 101(

5

~

-I

C4

;::

BASE

012

' -.01

4 I

FEEDBACK

3 u

I

R17

G)E-toc,o

nc,,

10K

250

-6.8V

REG. I 12v 12V

1

~

--

WD2109

SCHEMATIC

DIAGRAM

PLUG-IN

CIRCUIT

BOARD

&'

~

iii

~

2N1190

,__

~=

2N1193

luf

..,_ --

, RJ2

R:i,;

R35

R37

100.ll,

1K

220.!l

R34

100.n

--

I

11

Number

SECTION

VI

MCW-550

SCHEMATIC &PARTS LIST

Drawings &Prints Included

Title

WD-2091 Sheet 1,2 .

WD-2108.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

....

Schematic MCWSS0 &Parts List

WD-2109

........

.

WD-2110

........

.

WD-2091

Sheet

3,4,5,6

..

.Schematic Diagram -

Heat

Sink Subassemblies

. . Schematic Diagram -Plug

In

Circuit Board

. . . . . . . . . . . Circuit Board

Layout

WD-2308

..........................

. . . . Parts List -MCW-550

. . . . . . . . . . . . . . Block Diagram -MCW-550

10

-+t-

.

-+t--

e

~~

~

!

~®~

~1~

i~

;i

O e

W

-1-~,.._

10K~

~

2.7K

1W

V

,.

(.\

220.n

~

....,----....,

~

5.6K~

e

~

Q9

e,.;!.UMPE~

t;;:\ 5.0K

~

100.0.

100n

0

~

1.5K

1W

o-{§J-o

. 10K o-{EJ--o

~

Q

-"4-

2.7K1W

V

~22t<

~

1K

100n

0

~~

~

1K

1%

10K JUMPER

C2

33K Cg-1.0 MFD.

c():i.01

~

1K

100K 220.0.

~

~ ~ ~

Q JUMPER O

4.7K 15K

1K

+

C11

260 MFD.

12V

+ C10 260 MFD.

12V

a,_

...;J=UM;;.;..PE;;;;.;R'---

~~

' 0

~

10K

0.01

r::C)).01

c1

ca

WD

2100

CIRCUIT

BOARD COMPONENT

LAYOUT

( (

some

extent

on

the resistance

of

the

voltmeter.

In

a properly operating

unit

with Power

OFF

a

milliameter placed across

the

out-out

terminals

of

the

welder will indicate a

current

flow in

the

order

of

three

or

four milli-amperes.

The

"Power

at

Electrodes" indicates a condi-

tion

where

current

in

the

order

of

several

to

possibly more

than

a

thousand

amperes may

be available

at

the

electrodes

under

varying

degrees

of

fault conditions.

1.

It

is probable where

under

a

Fault

condi-

tion

excessive current has been drawn

that

one or more

of

the

Emitter

leads

of

the

Power Transistors has charred

or

burned.

These insulated

Emitter

leads serve as equal-

izing resistors in addition

to

their

role

as

connectors

to

the

common

Emitter

Bar.

Therefore, where replacement

of

these leads

becomes necessary,

they

should be replaced

with

leads

of

the

same gauge and length as

the

original.

DETAILED TROUBLE SHOOTING

CAUTION: DO NOT USE OHMETER

TO

TROUBLE-

SHOOT WHILE POWER IS APPLIED

Symptom: Excessive

heat

at

Weld Head Electrodes, evi-

denced

by

burning

of

material

with

little

or

no

control

from Weld Amplitude Selector.

There· are four general areas where malfunction could pro-

duce this symptom. Listed below are these general areas

in

most

probable order

of

occurrence:

1.

Power Transistor Assembly.

2.

Feed-Back wires to

Weld

Head. Note: This would

be

prime suspectwhere any work

or

rep]acement

of

head

had

been made

just

prior

to

development

of

symptom.

3. Driver Transistor Assembly.

4. Plug-in Printed Circuit Board.

A series

of

relatively simple elimination procedures will es-

tablish

the

area

of

the

malfunction.

1. Eliminating Power Transistor Assembly. Procedure:

(a)

Turn

Welder Power

OFF.

(b) Leave Weld Head and

Actuator

Cables

in

place.

(c) Temporarily connect a flash-light bulb across

weld

head

electrodes. (A

3.2

volt .15 ampere

bulb will be satisfactory.)

If

there is ANY de-

gree

of

illumination visible,

the

fault condi-

tion is in the Power Transistor Assembly. This

Assembly must be removed and

the

defective

Power Transistor(s) replaced.

It

is

recom-

mended

that

a complete replacement be made.

(d) Note: Under

NORMAL

conditions with Welder

Power

OFF

a Voltmeter placed across

the

Weld-

er

Output

Terminals will read approximately 5

volts due

to

normal leakage

of

transistors

in

the

circuit. Under these'NORMAL conditions, the

maximum current which can flow

with

a short-

ed

output

is

in

the

order

of

about

15-20 milli-

amperes.

(e) Note: Under a FAULT condition, voltage

across

the

Welder

Output

will be approximately

the same

as

(d) above. However,

the

maximum

current which can flow

under

shorted

output

conditions can be over a thousand amperes

for

a

short

period

of

time.

(f) Elimination procedure continues with

the

assumption

that

(

c)

above produced

no

indh

cation .of current flow.

2. Eliminating Feed-Back Wires

to

Weld Head. Pro-

cedure:

(

a)

Leave flash-light connected as in 1(c) above.

{b) Leave weld head and

actuator

cables in place.

(c) Momentarily

turn

Welder Power ON.

If

flash-light bulb illuminates,

turn

Welder Power

OFF.

(d) Remove voltage fire plug from welder recep-

tacle.

(e) Loosen

both

sensing wires from weld head

electrode assembly

and

lift free.

(f) Disconnect weld

head

from

output

of

welder.

(g) Using

an

Ohmmeter,

determine which elec-

trode terminates at

the

NEGATIVE

output

terminal

of

the welder. Mark this electrode

Negative. Do

the

same thing

to

the

electrode

which terminates

at

the

POSITIVE

output

ter-

minal

of

the

welder.

(h) Using

the

Ohmmeter

with

one lead connected

to

(2)

of

P-1

and

the

other

alternately touch-

ing the two sensing wires listed from

the

weld

head electrodes, connect the sensing wire which

shows continuity

with

terminal

(2)

of

P-1

to

the

weld

head

electrode marked NEGATIVE

in

Step

2g above.

(i) Transfer

Ohmmeter

lead

to

terminal

(1)

of

P-1

and

check

continuity

with remaining sensing

wire. Connect this sensing wire

to

the

POSI-

TIVE

electrode as det,ermined in

Step

2g above.

G)

Note: A strong possibility

of

error exists where

flexible leads are used from welder

output

to

weld head, or where a weld head

other

than

the

HughesVTA-66 is used;

(k) Note: Any suitable weld

head

may be employ-

ed

with this welder. However,

proper

connec-

tion

of

the

sensing wires MUST be observed.

Sensing wire

from

terminal

(2)

of

P-1

MUST

go

to

the

weld head electrode which

terminates

at

the

NEGATIVE

output

terminal

of

welder.

Sensing wire from terminal (1)

of

P-1

MUST

go

to

the

weld head electrode which

terminates

at

the POSITIVE

output

ter-

minal

of

welder.

(1)

Elimination procedure continues

with

assump-

tion

that

the

sensing wires were

found

to

have

continuity and were properly connected

to

the

weld head.

3. Eliminating Driver Transistor Assemb1y. Procedure:

(a) Remove power from welder and remove welder

7

4.

8

(b)

(c)

(d)

(e)

(f)

(g)

(h)

(i)

G)

from cabinet.

Disconnect

battery

cable from Positive terminal

of

battery.

Tape

end

and set aside. Reconnect

the lugged red/white wire

to

the positive

battery

terminal. This wire supplies

the

charging

current

to

the

batteries. ,

Inspect for

any

visible signs

of

overheating.

Remove

Q-~

Emitter

lead (gray wire

on

two

lug terminal' strip

on

top

pf

power

transistor

plate).

Connect Oscilloscope

input

leads across R-39

(the

center 10

ohm

resistor). Connect

the

Scope

common

to

the side

of

the

resi~tor

having the gray common wire.

AdjustScope

controls for:

Time/Div

of

2 milliseconds

Volts/Div for

.1

volt for a

ten

line grid

or

a

full scale of 1 volt

Scope trace

on

upger

grid

line

Adjust welder controls as follows: ·

Weld Duration: 2.0 Milliseconds

Weld Voltage:

.5

Volts

Connect

Test

Plug

to

J-1 welder. Connect

the

wire from(1)

of

test plug

to

POSITIVE out-

put

terminal

of

welder. Connect the wire from

(2)

of

test

plug

to

the stand-offinsulator men-

tioned in

(d)

above.

THESE

ARE

THE

SENSING WIRES AND

MUST

BE

CONNECTED.

While observing trace

on

Scope,

turn

welder

power momentarily ON. Trace normally will

drop

about

.003 volts and remain steady

at

that

point.

If

trace

drop

exceeds this value, turn

welder power

OFF.

Remove

printed.

circuit

board

from the· unit. Again while observing

trace,

turn

welder

power

ON.

If

trace drops

more than

about

.09 volts negative,

it

indicates

a

fault

in either

of

the 2N2137 Driver Transis-

tors.

Turn

welder power

OFF.

Move Scope in-

put

to

across R38

(the

100

ohm

2W

adjacent

to

R39).

Turn

power ON. Scope should indi-

cate

not

more

than

.2

volts negative. Partial

or·

complete failure

of

one or

both

of

the

2N2137 Transistors will produce voltage read-

ings other

than

given here. These

two

transis-

tors can be replaced

without

further

disassem-

bly

by

removing

the

two retaining screws

on

each

of

the

transistors and lifting

them

from

their sockets. Exercise care in replacing these

units. Make certain

that

the mica insulating

washer

is

in place

and

after inserting new trans-

istors in the sockets and securing

the

retaining

screws,

check

for

possible short

by

connecting

an

Ohmmeter

between retaining screw and wel-

der chassis. There should be NO continuity.

Eliminatingprocedure continues

on

assumption

that

in 3(i) above

with

the printed circuit

board

removed

from

the

unit,

the

voltage readings

obtained

on

the

scope did

not

differ greatly

from those· indicated for a normal operating

unit. This places the remaining area

of

fault

in

the

printed

circuit board.

Printed Circuit Board Check-Test. Procedure:

(a)

Test

conditions:

1.

Welder removed

from

cabinet. Power

OFF.

(b)

(c)

(d)

(e)

(f)

(g)

2.

Battery Cable disconnected from posifive

terminal

of

batte1y. Leave red/white wire

connected

to

baHery.

3. Remove Q-l-1'

Emitter

Lea1 (gray wire

on

two

lug

teditnal

.strip ·

on

.

top

of

power

transistor plate).

4.

Connect

Oscilloscope

input

across

R39

(

the

center 10

ohm

resistor).

Connect

the

Scope .common

to

the

side

of

the resistor

having the gray wire.

5. Adjust Scope controls for:

Time/Div

of

2 Milliseconds

Volts/Div

for

.1

volt for a

ten

line grid

or a full scale

of

l volt.

6.

Set

Welder controls

as

follows:

Weld Duration:

2.0

Milliseconds

Weld Voltage: .5 Volts

7. Connect the

Test

Plug

to

J-1

of

welder.

Connect

the

wire from

(I)

of

the

Test

Plug

to

POSITIVE

output

terminal

of

welder.

Connect

the

wire

from

(2)

of

Test

Plug

to

lugged orange wire remaining

at

stand-off

insulator mentioned above.

THESE ARE THE SENSING

WIRES

AND

MUST BE CONNECTED.

While observing trace

on

Scope,

turn

welder

power

momentarily

ON.

Trace will normally

drop

about

·.003 volts

and

remain steady

at

that

point.

If

in (b) above

the

trace dropped more

than

.003 and remains deflected, operate the Weld

Voltage Control and determine whether this

has any effect.

If

the Weld Voltage Control

has

no

effect, either Q8

and/or

Q9

may be

defective.

If

the

Weld Voltage does show con-

trol,

it

is more likely

that

QS

is

defective.

Having corrected fault condition indicated

in

(c) above,

tum

Welder Power ON. Trace

on

Scope should remain

at

point

indicated in 4(b).

Operate actuator. A negative going pulse

of

.5

volts

in

amplitude with a time base

of

approxi-

mately 2 milliseconds should be seen

on

Scope.

Set

Welder Voltage control

to

1.5 volts. Scope

should

now

show a 1.5 volt pulse.

If

the volt-

ages obtained are in excess

or

less

than

the

.5

and

1.5 selected, recalibration

of

the

voltage

stepping controls can be accomplished

by

alternately ·adjusting

the

two

trim

pots

on

the

circuit board.

The

200

ohm

pot

sets the mini-

mum

and the 1,000

ohm

sets the

maximum.

There is some inter-action between these two

adjustments; therefore, the high and low adjust-

men

ts

should be repeated as

often

as

necessary

to

make

the

output

coincide

with

Weld Voltage

Selector.

Set

Weld

Duration

to

1.0 second. Adjust

Scope

to

present a 1.0 second pulse. With

Weld Voltage Control set

at

.5

volts, close the

actuator

and hold closed while observing trace

complete

the

1.0

second pulse. Operate

actuator

again

but

release immediately. Trace

as

viewed

on

scope should immediately ter-

minate when actuator

is

released. Trace should

return

to

the no-signal level

without

hesitation.

If

the

pulse does

not

immediately terminate

without

actuator

but

instead drops

to

some

(

intermediate

point

and

then

finally cuts

off

at

the

end

of

the

1.0 second,

it

is

most

probable

that

Q4

is partially defective or developing ex-

cessive leakage and should be replaced.

CAUTION!!!

The sensing wires MUST, MUST be properly

SUGGESTED

TEST

PLUG

ACTUATOR:

ACTUATOR

VOLTAGE

FIRE

(@@\

~

WELDER RECEPTACLE

connected

AT

ALL TIMES either when

the

unit

is

in

normal operation

or

when

any

tests

or adjustments are being made.

In

ALL

of

the

test

procedures outlined above, the sensing

wires from the

test

plug have been

connected

as indicated

in

the

various steps.·

TO STAND

OFF,

AND ORANGE

LUG WIRE ON BLACK HEAT

SINK ASSEMBLY (R-39)

TO t OUTPUT TERMINAL

OF

WELDER

SECTION V

MCW-550

DUTY

CYCLE

CAPABILITIES

The following table shows various examples

of

weld voltage

and durations with

the

resultant weld circuit amperes and

possible

duty

cycles based

upon

continuous 8 -

16

hour

production days.

With

TWO

MILLIOHM

Load

WELD VOLTAGE

.75

1.00

1.35

With FIVE MILLIOHM

Load

.22

.

22

.

22

.22

WELD DURATION

5MS

I0MS

20MS

SMS

l00MS

500MS

1 Sec.

2Sec.

3 Sec.

In

many

cases

for

short periods

of

time, these

duty

cycles

can be considerably increased.

It

is particularly true when

welding for durations less

than

20

milliseconds.

AMPERES

400

495

675

50

DUTY

CYCLE

120 Welds per minute

60

Welds per

minute

30

Welds

per

minute

90

Welds

per

minute

30

Welds

per

minute

20

Welds

per

minute

IO

Welds

per

minute

5 Welds

per

minute

3 Welds

per

minute

* All

Currents

measured with 150 ampere/50 millivolt shunt

in

series

with

load.

9

Hughes MCW-550 User manual

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