Vhf engineering Ps 25 c/m User manual

b

INSTRUCTION

MANUAL

a

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Pu

INSTRUCTION

MANUAL

#5011222

R

ST.

/

BINGHAMTON,

N.Y.

13901

/

Phone

607-723-9574

320

WATE

SPECIFICATIONS

for

PS-25C,

PS-25M

Voltage

Output:

adjustable

10

to

15

volts

Load

Regulation:

2

percent

from

no

load

to

20

amps

Current

Output:

25

amps

for

50

percent

duty

cycle

14

amps

continuous

CunrentwLamicing-

foldback

limiting

to

1

amp

nominal

Ripple:

50

MV

at

20

amps

Operating

Temperature:

65

degrees

C

(149

degrees

F)

Maximum

at

14

amps

Meter

Accuracy

(PS-25M):

5

percent

of

full

scale

Fuse:

LOAS

force

hiv.

SA.

for

2

20V

LIMITED

WARRANTY

The

enclosed

warranty

card

must

be

filled

out

and

returned

within

10

days

of

purchase.

Units

are

warranted

for

90

days

from

purchase

date.

VHF

Engineering's

liability

is

limited

to

the

repair,

adjustment

or

replacement

of

units

of

the

original

consumer

purchaser

that

are

proven

defective.

R.F.

power

devices

are

warranted

to

be

within

1dB

of

specification.

Units

modified

or

operated

in

a

manner

not

consistent

with

the

instructions

in

the

manual

will

not

be

covered

by

this

warranty.

Defective

units

must

be

returned

to

the

factory

at

the

address

below

with

a

descrip-

tion

of

the

difficulty

and

the

date

of

purchase.

VHF

Engineering

is

not

liablegiee

any

damage

occurring

in

shipment,

so

the

unit

should

be

packed

properly.

The

customer

must

pay

all

shipping

costs.

Further

information

may

be

obtained

by

calling

VHF

Engineering's

Customer

Service

Department

at

(607)

723-9574

(collect

calls

will

not

be

accepted)

or

writing:

Customer

Service

Department

VHF

Engineering

320

Water

Street

Binghamton,

New

York

13901

The

consumer

must

pay

all

shipping

costs.

No

other

warranties

are

expressed

or

implied.

VHF

Engineering

is

not

responsiblem

foe

damages

which

result

as

a

consequence

of

or

incident

to

using

this

junit.

Some

states

do

not

allow

limitations

on

how

long

an

implied

warranty

lasts,

so

the

above

limitation

may

not

apply

to

you.

Some

states

do

not

allow

the

exclusion

‘or

limitation

of

incidental

or

consequential

damages,

so

the

above

limitation

may

not

apply

to

you.

This

warranty

gives

you

specific

legal

rights,

and

you

may

also

have

other

rights

which

may

vary

from

state

to

state.

4-10-78

ADDENDUM

TO:

PSSOLZ

PS25

Series

PSt5

PS3A

Repeater

Manuals

Either

550

or

723

regulator

IC's

may

be

used

on

the

PS3A

regulator

board.

The

values

of

Rl

and

R3

are

specified

as

follows:

forea

550

1C,..-Kk1l)=

1K

ohm,

R3

=

10K

for

a

723

IC,

Rl

=

5.6K

ohm,

R3

=

4.7K

ohm

R5

and

R6

determine

the

foldback

current

limiting

characteristics

of

the

supplies

to

limit

the

short

circuit

current

to

less

than

2

amps.

They

are

specified

as

follows:

R5 R6

R7

PS3012

330

ohm

3.3K

100

ohm

PS25

Series

330

ohm

3K

100

ohm

PS15

390

ohm

3K

100

ohm

Repeaters

390

ohm

3K

100

ohm

PS3A

Modules

390

ohm

3K

.l

ohm

*

*If

the

PS3A

is

used

with

external

pass

transistors,

change

to

100

ohm.

For

the

PS3012

only,

R5

has

a

1

mfd

capacitor

placed

across

it

on

the

top

of

the

board,

and

C3

is

replaced

on

the

board

by

a

220

ohm

2

watt

resistor.

This

sheet

is

to

be

included

with

all

of

the

above

manuals.

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INSTRUCTION

MANUAL

TABLE

OF

CONTENTS

SECTION

SPECIFICATIONS

WARRANTY

0

DESCRIPTION

Tat,

INSTALLATION

TT:

OPERATING

INSTRUCTIONS

IV.

THEORY

OF

OPERATION

ae

ADJUSTMENT

VI.

SERVICING

VIL.

CUSTOMER

SERVICING

SCHEMATIC

DIAGRAM

PARTS

LIST

PARTS

LAYOUT

(1)

COVER

II

COVER

IL

PAGE

Ok.

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ee

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gl

TVe

DESCRIPTION

The

PS25C/M

is

a

solid

state

regulated

power

supply

with

an

inter-

nally

adjustable

operating

voltage

of

7

to

14

volts.

The

power

—

supply

will

provide

2%

regulation.

for

load

currents

up

to

20

amperes

and

is

capable

of

supplying

up

to

25

amperes

with

a

duty

cycle

of

50%

(a

maximum

"'on"

time

of

3.minutes)ae

Ine

Pol

5G,

eas

an

over

voltage

protection

(0.V.P.)

device

and

foldback

current

limiting.

The

PS25M,

the

metered

version

of

the

PS-25C,

has

two

edgewise

meters;

a

0-20

volt

DC

voltmeter

and

a

0-30

ampere

D.C.

ammeter.

INSTALLATION

Simply

plug

the

unit

into

a

suitable

A.C.

outlet

and

connect

the

load

to

the

binding

posts

being

careful

to

observe

the

proper

polarity.

If

the

power

supply

is

located

some

distance

from

a

high

current

load,

heavy

gauge

wire

(#12

or

#10)

should

be

used

to

prevent

apparent

loss

of

regulation

due

to

the

voltage

drop

in

supply

wires.

The

unit

is

preset

at

the

factory

to

deliver

13.8VDC.

OPERATING

INSTRUCTIONS

After

installation,

the

power

supply

need

only

be

switched

on

or

OE:

Because

the

fuse

is

in

the

A.C.

line,

it

is

recommended

the

power

supply

be

unplugged

when

changing

fuses.

The

fuse

should

be

rated

at

10-amperes

for

110

volts

(5

amperes

ton

22Z00yel"

Gnie

It

is

important

to

ensure

that

the

total

load

attached

to

the

power

supply

is

within

its

ratings.

Those

loads

near

the

upper

limits

of

the

ratings

may

exceed

the

power

supply

ratings

during

turn-on

(especially

tube

type

equipment

where

tube

and

lamp

fila-

ments

may

represent

a

lower

resistance

when

cold).

Be

sure

to

read

the

paragraphs

foldback

current

limiting

as

detailed

in

the

Theory

of

Operation

Section.

THEORY

OF

OPERATION

The

center

tapped

secondary

of

the

power

transformer

is

connected

to

dual

diode

Dl

to

form

a

full

wave

rectifier.

The

rectified

D.C.

from

DL

is

filtered

by

a

large

filter

capaciconr

Clarnca

to

the

pass

transistor

assembly

and

the

regulator

circuit

(Poa

The

heart

of

the

regulator

circuit

is

the

NE550

ox

/23

precision

voltage

regulator

I.C.

It

contains

a

precision

zener

reference

voltage,

an

error

amplifier,

an

on-chip

pass

transistor,

and

cur-

rent-foldback,

transistor

network.

The

reference

voltage

is

com-

pared

to

a

portion

of

the

power

supply's

output

voltage

(Vs)

determined

by

Rl,

R2,

and

R3.

The

error

amplifier

amplifies

any

(2)

difference

and

applies

a

correction

voltage

to

the

on-chip

pass

transistor

to

raise

or

lower

the

output

voltage,

as

required,

until

the

desired

output

voltage

is

maintained.

To

provide

greater

current

capacity,

external

pass

transistors

SEeecemnieered

into

ithe

circuit.

A

TIP3055

transistor

is

used

to

bring

the

current

capacity

to

a

level

necessary

to

drive

the

pass

transistor

assembly.

The

pass

transistor

assembly

consists

of

four

transistors

connected

in

parallel

with

small

valued

resistors

in

the

emitter

leads

to

provide

correct

equalization.

Foldback

current

limiting

is

provided

to

limit

the

output

current

Preece

supply

in

the

event

of

an

accidental

short

circuit.

The

foldback

circuit,

in

essence,

monitors

the

impedance

of

the

load.

When

this

circuit

sees

too

low

an

impedance,

such

as

a

short

cir-

cuit,

the

output

current

is

reduced

to

a

low

continuous

value

of

about

1

amp.

Foldback

limiting

is

a

valuable

safety

feature

in

a

power

supply

since

it

can

prevent

malfunctioning

equipment

from

being

damaged

by

excessive

currents.

The

foldback

circuitry

can,

however,

be

fooled

under

some

circumstances

and

power

supply

oscillations

can

occur.

Consider

the

case

where

a

high

power

amplifier

is

being

powered

by

the

supply.

Assume

that

the

amplifier

draws

26

amps

during

startup

and

has

a

relay

in

its

supply

lead.

When

the

relay

pulls

in,

the

amplifier

will

attempt

to

draw

26

amps,

but

the

foldback

limiting

current

will

lower

the

supply

voltage

to

limit

the

current

to

1

amp.

The

relay

will

drop

out,

the

foldback

circuit

will

put

the

supply

back

to

normal,

the

relay

will

pull

in

again

causing

the

amplifier

to

attempt

to

draw

26

amps,

the

Pordpack

Circuit

will

reduce

the

voltage,

and

so

on.

The

output

voltage

of

the

power

supply-amplifier

combination

will

now

be

oscillating.

Oscillations

of

this

type

can

be

prevented

by

making

sure

that

startup

and

operating

loads

are

below

the

rated

current

for

the

SuppLy4

feGonsinuing.oscidtlations,of

this

type

may

cause

the

over-

voltage

protection

circuitry

to

short

the

output

of

the

supply

to

ground.

The

over-voltage

protection

device

(the

0.V.P.)

protects

the

equipment

being

powered

in

the

event

of

a

power

supply

malfunc-

tion.

If

the

power

supply

voltage

exceeds

15V,

the

output

of

the

supply

will

be

shorted

to

ground.

The

0.V.P.

will

also

operate

if

series

of

pulses

greater

than

15V

is

generated

by

the

load.

If

unwanted

O.V.P.

triggering

should

occur,

turn

the

supply

off

rewelemirnutle

to

reser

the,O0.Vr.2.

(3)

V...

ADJUSTMENT

1.

Unplug

the

power

cord.

Remove

the

six

#6

x

3/8

self

tapping

screws

on

the

side

of

the

cover

which

hold

the

cover

to

the

chassis.

Remove

the

cover.

2ReISGE

the

voltage

adjust

control

(R-2)

on

the

regulator

circuit

boardstocnid!

posstion-

3.

Connect

a

volt

meter

to

the

output

terminals.

Set

the

meter

to

read

20-50

volts

full

scale.

Use

the

panel

meter

for

the

PS25h

4.

Plug

in

supply

and

turn

switch

on.

Adjust

R-2:.for

a

nominal

L3

tsi

voltssourput.

5

If

the

control

is

adjusted

-above

IS

wolts,.

the

O.Va-sawia

shut

down

the

supply.

The

O.V.P.

is

reset

by

turning

off

the

supply

for

approximately

one

minute

ie

sure

to

reset

control

tosmiditpos

Ltion)%

6.

Turn

the

supply

off

and

unplug

the

power

cord.

7.

Place

the

cover

on

the

chassis

with

the

beveled

end

toward

the

front.

Line

up

the

mounting

holes

with

the

Tinnerman

fasteners

and

secure

the

cover

using

six

#6

x

3/8

self

tapping

screws.

VI.

SERVICING

NO

OUTPUT

iy

Checks

fuse

or

circuit

breaker:

2.

The

over-voltage

protection

device

may

be

shutting

down

the

Supply

-as

soon

°as*it°is

turned?%on=~-/To4+reset

tie

10.V

an.

Turn

the

power

off

-

wait

about

one

minute

for

the

filter

capacitor

to

discharge

-

turn

the

regulator

pot

down

(see

Adjustment

Section)

-

reapply

power

-

adjust

the

regulator

pot

for

the

desired

output

voltage.

3.

Measure

voltage

across

filter

capacitor.

ay)

4L£c022=+25

VDC

is

present,

proceedVtorstep

yy.

b.)

If

no

voltage

is

present,

proceed

to

step

4.

Check

the

bridge

rectifier

for

shorts

or

open.

5.

Check

the

power

cord

continuity.

6.

Check

the

transformer

primary

and

secondary

for

continuity.

(4)

7.

Measure

the

voltage

at

the

base

of

the

pass

transistor

on

the

PS3A

card.

This

measurement

can

be

made

at

the

"VO"

terminal.

a.)

If

no

voltage

is

present,

proceed

to

step

10.

b.)

If

12-24

volts

is

present,

proceed

to

step

8.

Check

the

pass

transistor

on

the

PS3A

card

for

open

junctions.

@.

Gheck

the

.1

ohm

resistors

for

open

circuit.

10.

Measure

the

voltage

at

the

base

of

Ql.

a.)

If

the

reading

is

12-24

volts,

Ql

may

be

defective

(see

test

chart

below).

Check

carefully

for

cold

solder

joints.

De

j)ts

the

reading

is

0

volts,-proceed

to

step

11.

Pe

Check

the

voltage

at.

-ICl

4.

fee

Cece

reading.

us

over

i

oO

volts,

check

Rl,

R2

and

.R3,.for

open.

b.)

If

the

reading

is

below

1.6

volts,

check

the

voltage

on

LGl-pins—lLiwand-12..-~Li-sieeis-pbetween:

22-24-volts,

~I1Cl.may

Dewbad.

Lf

-iteis

0.

volts...

check,

for;

open

land

or

cold

sol-

der

joints

on

circuit

board.

VOLTAGE

DROP

UNDER

LOAD

1.

Reduce

the

load

and

recheck

the

output

voltage.

The

current

limit

will

reduce

the

output

voltage

if

a

load

greater

than

the

supply

can

handle

is

applied

(see'Theory

of

Operation").

2.

Check

the

voltage

across

the

filter

capacitor

(Cl)

under

load.

a.)

If

the

reading

is

under

20

volts,

proceed

to

step

4.

b.)

If

the

reading

is

20-24

volts,

proceed

to

step

3.

Check

the

solder

connections

to

the

front

panel

output

terminals.

Be

sure

that

the

screws

which

hold

the

PS3

in

place

are

tight.

feeeecheck

diode

Dil

for

an

open

junction.

5.

Check

the

solder

connections

between

the

transformer

and

mectitier.

6).

.pe

sure

that

the

screws

which

hold

the

PS3

in

place

are

tight.

Peeeeneck

Ol

stor

an

open

junction

(See

chart

below).

If

Ql.

checks

good,

ICl

may

be

bad.

(5)

ele

Ee

EXCESSIVE

RIPPLE

OR

HUM

Ls

Be“sure

that’

“the

screws

which

hold

the

P53

an

place

ate.

cole

2.

Check

the

bridge

rectifier

for

open

or

shorted

diodes.

3.

Check

line

voltage.

Excessively

low

line

voltage

may

cause

hum

under

heavy

loads.

Lowering

the

output

voltage

of

the

supply

may

correct

this

problem.

VHF

Engineering's

Customer

Service

department

will

assist

custo-

mers

with

technical

problems

concerning

all

VHF

Engineering

units.

If

you

have

a

query,

please

contact

the

Customer

Service

Depart-

ment

at

(607)

723-9574.

Units

having

serious

problems

may

be

returned

postpaid

to

the

factory

without

authorization

for

evalua-

tion

and

repair

estimates

with

a

note

detailing

the

difficulty.

Units

qualifying

for

warranty

service

will

be

covered

according

to

the

warranties

detailed

in

their

manuals.

For

units

not

covered

by

a

warranty,

a

nominal

service

fee

plus

parts

and

return

postage

will

be

charged.

Units

returned

for

service

should

be

Sé@mt.

0%

Customer

Service

Department

VHF

Engineering

320

Water

Street

Binghamton,

New

York

13901

(6)

PARTS

LIST

Got

25000

MFD

40

volt

2010610

R

1

tk

5Z

2020230

Coz

E001

2010370

RZ

2Ke

Pot

2020510

Crs

470

MFD

16

volt

2010570

R23

LOK

S56

2020329

C4

.OO01

2010370

R

4

5.6K

4W

2020300

Cus

SOL

2010410

RO

330

ohm

5%

2020175

C

6

OL

2010410

R

6

Bea

7

2020261

Re

100

ohm

1W

2020110

D1

30

amp

PIV

Rectifier

1010120

R

8

.lL

ohm

5W

2020010

R

9

.L

ohm

5W

2020010

1G

NES50

1050050

R1O

.l

ohm

5W

2020010

R11

.1

ohm

5W

2020010

Orr

TLE

30D

1020060

RZ

220

ohm

2W

2020140

Ori

2N3055

or

Equiv.

1020050

8

ae

2N3055

1020050

S

tL

SPST

Switch

3010050

Q

4

2N3055

1020050

Qe

2N3055

1020050

el

Power

Transformer

4010020

36V

CT

@

25

amps

P.-C.

Board

4040220

110/220

volt

primary

FI

3

Woy

:

Hardware,

Heat

Sinks,

Chassis

and

Wire

FOR

PS25M

ONLY

Edge

Reading

D.C.

Ammeter

(0-30

amperes)

Edge

Reading

D.C.

Voltmeter

(0-20

volts)

PS25M

Chassis

3050390

300391

4030120

(oe)

Qe

pay

|

10

Ql

ess

ck

R4

i

QS

=

Ola

2

Co

|

Gl

er

+

3R5

]

|

|S

sii

|

DIb

|

Z

C4

eRe

a

R8

RQ

|

a

e

S>

o-

2

4

=FOR

PS25M

ONLY.

”

;

ad

46

SRO

‘4

7

>

wer

>

ee

2g

e0euN

oe

on

emoneeenen

pb

aN)

3

ite

HLEIKYK

ae

WETAL

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|

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eels

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BOO:

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(03.9

VHF Engineering PS 25 C/M User manual

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