EHRHORN ALPHA 77Sx Manuel utilisateur

Ce manuel convient aux modèles suivants

1

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PRICE: $10.00

OPERATING AND TECHNICAL MANUAL

HIGH FREQUENCY LINEAR POWER AMPLIFIERS

ALPHA 77Dx an ALPHA 77Sx

EHRHORN TECHNOLOGICAL OPERATIONS, INC.

JANUARY 1990

IMPORTANT

SERVICE ASSISTANCE

To help you secure technical assistance without waste long istance calls, ETO

has establishe a special SERVICE telephone line WHICH WILL BE ANSWERED

ONLY WHEN A QUALIFIED SERVICE TECHNICIAN IS AVAILABLE TO HELP

YOU IMMEDIATELY.

The special service number is (719) 599-3861. If your call to this number is NOT

answere it in icates that no qualifie technician is free to talk with you at the

moment. Please wait a few minutes an try again. NOTE ALSO that business

hours are 8:30 A.M. to 4:30 P.M. MOUNTAIN TIME Mon ay through Thurs ay.

If your call oes NOT relate to service or other technical matters, our business

office staff will be happy to help you at the number shown on the rear cover of

this manual.

TEN METER OPERATION OF YOUR ALPHA

FCC rules permit an appropriately license amateur to mo ify his own amplifier

for operation on 28-29.7 MHz. We strongly recommen that you contact our

service epartment before attempting any mo ification. (If you enclose your

request an a photocopy of your vali amateur ra io license with the warranty

registration car for your new amplifier, appropriate information will be sent

without charge.)

THE EXPECTED NEW 10, 18 an 24 MHz AMATEUR BANDS

If an when FCC permits amateur use of these ban s with linear amplifiers,

your ALPHA will be capable of 10 an 18 MHz operation with only slight mo i

fication. In the somewhat unlikely event that high power operation is eventually

permitte on 24 MHz, ETO may make available information to permit safe operation

of your ALPHA on that ban . ANY ATTEMPT TO OPERATE YOUR ALPHA IN

THE VICINITY OF 24 MHZ WITHOUT APPROPRIATE MODIFICATION MAY

CAUSE SERIOUS DAMAGE.

1/90

TABLE OF CONTENTS

SECTION 1 - GENERAL DESCRIPTION & SPECIFICATIONS

.........

1

SECTION 2 - INSTALLATION

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

2

Electrical Installati n (AC P wer Wiring) . . . 2

RF and C ntr l C nnecti ns

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

5

SECTION 3 - OPERATION

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

8

C ntr l P siti ns .......................... 8

Tune-up Pr cedure . .

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

9

Final Operati nal Adjustments «Sc M nit ring . . 11

Operating N t e s

.........

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

12

Tr ublesh ting Hints .

.

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

14

SECTION 4 - THEORY OF OPERATION

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

16

SECTION 5 - ILLUSTRATIONS

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

21

Fr nt Panel; Rear Panel

.

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

21

Fr nt Sub-panel; Back Side f Fr nt Panel . . 22

RF Secti n, T p and Side, C vers Rem ved . . 23

P wer Supply Secti n, Side and Oblique .... 24

Tube Deck, Underside; Circuit B ard CB-2 . „ . 25

Circuit B ard CB-3; Wattmeter „ . . . . . . . 26

Schematic, RF Secti n & Tube D e c k

.........

2?

Schematic, P wer Supply & Main Chassis .... 28

Schematic, Fr nt Panel

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

29

Schematic, Circuit B ard CB-2

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

3°

Schematic, QSK Circuit B ard CB-3

.........

31

SECTION 6 - STANDARD ELECTRICAL PARTS L I S T

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

32

ET0/"ALPHA" PRODUCT WARRANTY

...........

Outside Back C ver

EHRHORN TECHNOLOGICAL OPERATIONS, INC.

4975 NORTH 30TH STREET

COLORADO SPRINGS, COLORADO 80919 U.S.A.

REV. 1/90 @ U.S.A.

I

SECTION 1

GENERAL DESCRIPTION

The ALPHA 77Dx (type accepted m del PA-77DF and g vernment/exp rt

m del PA-77Dx)* is a high p wer HF linear amplifier f excepti nal

quality, ruggedness, and s phisticated design. It is much smaller

than ther amplifiers f c mparable capability, yet pr vides great

er perati nal versatility, c ler perati n, and a l wer ac usti

cal n ise level than much larger and heavier units.

Unique design features f the ALPHA 7?Dx include ETO's exclusive

full-cabinet ducted air c ling system, built-in CW break-in key

ing system, frequency c verage d wn t 1.8 MHz, and a highly effi

cient cust m p wer transf rmer using a tape-w und c re f grain-

riented silic n steel. High efficiency f perati n is maintained

acr ss the tuning range by a c mbinati n f vacuum variable utput

tuning capacit r and ETO's expertly designed mixture f silver plat

ed, heavy c pper tubing c ils and multi-insulated, t r idal induct rs.

SPECIFICATIONS (M dels PA-77DF and PA-77Dx)

Frequency C veragei 1.8-2.0 and 3-24 MHz (*24-30 MHz, PA-77Dx nly).

Plate P wer Input» PA-77DF 2.5 KW PEP/SSB, 1 KW average d-c, all

m des, n time limit» PA-77Dx 3*5 KW PEP, 2 KW d-c average, NTL.

Plate Efficiency» Typically 60# r better.

Drive P weri N minal 60-70 watts carrier, 100-150 watts PEP.

Input & Output Impedances» N minal 50 hms unbalanced * VSWR under 2*1.

Dist rti n: Third rder IM m re than 36 dB bel w 1.5 KW PEP utput.

Harm nics» M re than 50 dB bel w mean fundamental frequency utput.

Tube C mplement» One Eimac 8877 ceramic tri de, gr unded grid.

C ling» Full-cabinet ducted f rced airj ball bearing centrif. bl wer.

ALC» Adjustable-thresh ld, grid-current-derived, negative g ing.

Pr tecti n» Primary and step-start fuses, plate vercurrent s len id,

a-c line and high v ltage c ver interl cks.

Primary P wer» 220-250V with gr unded center neutral, 50-60 Hz, stan

dard. Simple re-c nnecti n acc mm dates 110-125V, 120-208V, r

220-250V with ut center neutral. 240V supply with 20A fuses r

sl w breakers is adequate f r all-m de perati n at full ratings.

Size & Weight» ll"h. x 19"w. x 22"d. (28 x 48 x 56 cm). Net weight

95 lb. (43 kg), shipping weight 125 (57 kg) in tw cart ns.

VARIATIONS FOR GOVERNMENT/EXPORT-ONLY MODEL ALPHA 77Sx (PA-77Sx)t

Same as ALPHA 77Dx (PA-77Dx) ab ve except tw 8877 tubes permit

greater PEP input and utput p wer. Appr ximately 175 watts

drive f r maximum utput. Net wt. 105 lb. (48 kg), shipping

weight 130 lb. (59 kg).

*N0TE: Only FCC type-accepted model PA-77DF may legally be sold ithin the U.S,

except to government customers. PA-77Dx £ PA-77Sx available only for

export and government customers.

-1-

SECTION 2

TNSTALLATT ON

1. Unpacking: Carefully rem ve amplifier and transf rmer fr m car

t ns; SAVE ALL PACKING MATERIAL FOR RE-USE — SHIPMENT OF ALPHA

77DXIN OTHER THAN FACTORY PACKING MAY RESULT IN DAMAGE NOT COVERED

UNDER WARRANTY ©£©

Rem ve t p c ver and insure that b th plug-in circuit h ards are

firmly seated in their s ckets. C nfirm that the TUNE c ntr l

perates sm thly and reaches a firm mechanical st p at its full

cl ckwise r tati n. If y ur TUNE c unter reading decreases with

cl ckwise r tati n, it sh uld st p "between 000 and 010; if it is

a type that increases with cl ckwise r tati n f the crank, it

sh uld st p near 190-200. There is n hard st p at full c unter

cl ckwise r tati n and cauti n must be used t av id turning the

crank bey nd the n rmal end f r tati n (c unter reading f

appr ximately 240 r 000, depending n type as ab ve).

Inspect inside and ut cl sely f r evidence f shipping damage;

if any is f und, n tify delivering carrier at nce. C mplete

the encl sed warranty registrati n f rm and mail it t ET0. ©

2. Transf rmer Installati n: Orient the transf rmer s that the tw

multi-pin, m lded plugs n the transf rmer harness p int t ward

the rear f the amplifier; m ve the c rresp nding mating c nnect

rs in the amplifier ut f the way, and make certain that the

transf rmer m unting area is clear f packing material and all

wires. USE EXTREME CAUTION LOWERING THE TRANSFORMER INTO PLACE

TO AVOID DAMAGING ADJACENT COMPONENTS OR WIRING. It may be de

sirable t rig a simple sling f

str ng c rd r glass filament tape t aid in supp rting and c n

tr lling the heavy transf rmer while l wering it int place.

Install the b lts pr vided t secure the transf rmer. Check b th

pairs f c nnect rs visually f r pr per mating rientati n (av id

excessive harness bending r twisting, as it may cause damage t

wires r c nnect r pins) and mate them firmly, pushing until the

integral latches engage. Insure that all wires are dressed well

clear f the HV rectifier b ard and HV-sh rting cr wbar switch.

Make certain that the cr wbar arm swings freely. THIS CROWBAR

IS AN IMPORTANT SAFETY FEATURE; DO NOT DISABLE IT AND DO NOT ©

APPLY AC POWER TO THE AMPLIFIER WITH THE COVER OPEN.

3» Electrical Installati n: The ALPHA 77Dxand 77Sxare n rmally ship

ped wired f r U.S.-standard 120/240V (120-N-120), 3 wire, 50-60

Hz, single phase p wer (gr unded neutral). If the amplifier is

t be used with this service c nfigurati n r has been fact ry-

c nnected f r y ur alternate arrangement, the t p c ver may be

replaced and secured. If change- ver t perate n 220-250V

with ut center neutral, r n 110-125V service, is necessary,

pr ceed as f ll ws first*

Re-c nnecti n f r perati n n 220-250V with ut center neutral -

(a) L cate the 7-lug tie strip at the right, rear f the cabi

net, al ng the right edge f the circuit b ard shelf. The

lugs n this strip (TS-1) are numbered fr m #1 at fr nt t

-2

#7 at the back. The standard wiring t TS-1 (f r 120/240V

with center neutral) is as f ll ws* (See Fig. 1, page 4)

LUG 1 — Gr und (m unting f t f r terminal strip)

LUG 2 — White/black wire

LUG 3 — White wire

LUG 4 — Green, red, white/green & white/ range wires *

LUG 5 — White/vi let wire and ne bl wer wire (gray r blk)

LUG 6 — Black wire *

LUG 7 — Gr und f t; gray wires

* A tubular capacit r is c nnected als fr m #4 t #6.

(b) Rem ve the white/green wire nly fr m LUG 4 and c n

nect it instead t LUG 2. (See Fig. 2, page 4)

(c) Add a new resist r (700 hms, 8 t 12 watt) between

LUG 3 and LUG 4; keep it clear f all wires and parts.

(d) Rem ve the c ver fr m the 6 pin c nnect r n the AC

p wer cable; rem ve the wire jumper c nnected between

pins 10 and 11. Pin 11 is then blank and unused; nly

the green p wer cable wire (chassis) g es t pin 10.

(e) Replace p wer c nnect r c ver and amplifier t p c ver.

(f) The 240V service wires c nnect t black and white wires

f the cable; green g es t gr und nly.

Re-c nnecti n f r perati n n 110-125V service - All required

re-c nnecti ns are made inside the p wer cable c nnect r itself;

rem ve its c ver. (See Figure 5» page 4)

*

(a) Rem ve the existing jumper wire between pins 7 and 9«

Rem ve als the jumper wire between pins 10 and 11.

(b) Add a new jumper wire fr m pin 7 thr ugh pin 12 and n t

pin 11. Add an ther jumper wire fr m pin 8 t pin 9.

Replace cap n c nnect r.

(c) The 120V AC service wires c nnect t the black (fr m pins

8 & 9) and white (fr m pins 7i 11» & 12) p wer cable wires.

The green wire (chassis) c nnects t p wer system gr und.

F r inf rmati n n use with any ther type f primary mains c n

figurati n, c ntact ET0 fact ry.

P wer Cable C nnecti ns - The green wire in the main amplifier

AC p wer cable is c nnected t chassis and must always (and nly!)

be wired t the AC mains gr und ( r center neutral with U.S. stan

dard 120-N-120V system). The black and white wires are inter

changeable and c nnect t the tw "h t" wires f the service.

Service wiring sh uld be at least #12 AWG c pper, pr tected by

fuses r breaker rated at 20 t 30 amperes (#10 AWG, 30 ampere

fuses r breaker f r PA-77SjJ .

4. Physical L cati n: The amplifier must be p siti ned h riz ntally,

and s that the intake f c l air and exhaust f h t air is n t

impeded in any way, and s that h t exhaust air cann t signifi

cantly recirculate back int the c l air intake area. A minimum

f six inches clearance sh uld be all wed behind the amplifier,

with pen access t surr unding air unless special ducting pr 

visi ns are pr vided.

-3

Figure 1: Standard TS-1 wiring

f r 120V r 120/240V AC mains.

(rear)

d>

©—

(fr nt)

gray wires (mtg.)

black wire

wh/vi ., bl wer

grn., red,

wh/green*

white

wh/black

wh/ rg.

N/C (mtg. f t)

Figure 2: TS-1 wiring m dified

f r 240V with ut center neutral.

(See als Figure 4.)

(zfc

<k

© -

gray wires

black wire

w.

h/vi ., bl wer

Grn., red, wh/ rg

White

Wh/black

Wh/green *-

N/C

Figure 3? P wer cable c nnect r

wiring f r standard 120/240V

service (center neutral).

-<2>

d>

L ®

r © -

black wire

a

green wire

240V

(h t)

120vT

(neut

120 V

)

white wire (h t)

Figure 4: P wer cable c nnect r

wiring f r 240V with ut center

neutral" (See als Figure 2.)

- 0

d>

© -

black wire (h t)

A

green wire (gnd.)

240V

i

white wire (h t)

Figure 5: P wer cable c nnect r

wiring f r 120V service.

-d>

k D

© -

black wire (h t)

green wire (gnd.)

|!2°V

white wire (h t)

-4-

5. RF And C ntr l C nnecti ns: Interc nnecti n f the ALPHA 77Dx

( r 77S$ with any p pular transceiver r exciter f r c nventi nal

PTT, VOX, r manually-c ntr lled T/R perati n is straightf rward.

Special pr visi ns are inc rp rated f r full CW break-in r fast

VOX perati n with transceivers/exciters s equipped.

Rear panel c nnecti ns and functi ns are as f ll ws:

RF INPUT - Use a standard "BNC" plug and RG-58C/U cable t c n

nect t the 'rf utput' r 'antenna' jack f the exciter ( r

transceiver). NOTE: The antenna is fed directly thr ugh the

amplifier's internal change ver relays back t this RF INPUT jack

when the ALPHA is in OFF, STANDBY, r receive c nditi ns, permit

ting n rmal recepti n and exciter- nly transmissi n PROVIDED THAT

THE RECEIVER ANTENNA slide switch n the rear f the ALPHA is in

its NORMAL Tthr ugh) POSITION. This arrangement permits the use

f c nventi nal transceive-type rf interc nnecti ns, even f r CW

break-in. (See Figure 7-)

RF OUTPUT - NEVER OPERATE THE AMPLIFIER WITHOUT A PROPERLY MATCHED

LOAD CONNECTED TO THIS JACK'.© Use a standard PL-259 ("UHF"-type)

plug and RG-8A/U r equivalent cable f r c nnecti n t antenna

system r dummy l ad.

RELAY - After the required (3 minute n minal) tube warm-up

peri d has elapsed, a sh rt-circuit placed acr ss this jack will

switch the amplifier t the transmit c nditi n, pr vided the fr nt

.panel CW r SSB butt n (n t STBY) is depressed. Rem ving the ex

ternal sh rt all ws the internal change ver relays t return t

the receive r "thr ugh” c nditi n. The speed f the vacuum relay

circuitry in the ALPHA 77^x(and 77Si is sufficient t f ll w key

ing at speeds f 5° WPM r m re. T pr tect the vacuum relays

fr m damage due t "h t" rf switching (in all m des), an internal

rf interl ck circuit prevents them fr m cl sing if excitati n is

already present when the external RELAY c ntr l line is cl sed,

and als prevents them fr m pening - even if the RELAY line is

pened up - as l ng as rf excitati n is present.

RECEIVER ANTENNA switch - This slide switch MUST^ BE IN THE THRU

POSITION f r perati n with c nventi nal transceive-type c nnec

ti ns as described ab ve. In THRU, t the antenna will be fed thru

t the RF INPUT jack whenever the amplifier is in OFF, STANDBY, r

receive. permitting n rmal recepti n and exciter- nly transmissi n.

In the SEPARATE p siti n, the antenna ( r ther l ad) is c nnected

nly t the AUXILIARY receiver antenna jack under these c nditi ns.

THERE IS THEREFORE NO LOAD CONNECTED TO THE RF INPUT JACK AND

STRAIGHT-THROUGH EXCITER OPERATION IS NOT POSSIBLE.© (See Fig. 6.)

AUXILIARY receiver antenna - As described ab ve, this jack pr 

vides an alternate (and the nly) receiver antenna c nnecti n

when the RECEIVER ANTENNA slide switch is in its SEPARATE p si

ti n and the amplifier is in OFF, STANDBY, OR receive.

KEY - This ("RCA" r "ph n " type) jack may be used t .c ntr l

the CW keying, PTT, r ther T/R functi n f the exciter while

insuring pr per sequencing f the T/R change ver switching. The

ALPHA 77Dx(and 77$0 pr vides at this jack an is lated c ntact

5-

cl sure which f ll ws the keying imp sed externally n the RELAY

jack,with ne restraint: the utput KEY line d es n t cl se until

the amplifier's internal change ver relay c ntacts have actually

cl sed. The KEY line pens immediately, h wever, when the input

line t the RELAY jack is pened. When the amplifier is in OFF r

STANDBY, the RELAY jack is c nnected thr ugh t the KEY jack.

High speed CW break-in r VOX is available with ut auxiliary T/R

switches and with ut danger f "h t switching" high p wer rf -- ©

PROVIDED THAT THE TRANSCEIVER OR TRANSMITTER-RECEIVER USED IS

ITSELF CAPABLE OF BREAK-IN KEYING — by patching the CW key ( r

VOX relay c ntacts) directly int the ALPHA'S RELAY jack, and

patching the amplifier's KEY jack utput back int the exciter

key jack ( r, f r VOX, int the line n rmally c ntr lled by the

VOX relay c ntacts). (See Figure 8.)

By using the amplifier's AUXILIARY receiver antenna jack t pr 

vide the receiver's antenna input, full break-in CW perati n is

p ssible with many separate transmitter-receiver c mbinati ns

that d n t themselves inc rp rate adequate T/R antenna switching

f r break-in. BECAUSE THERE IS NO EXCITER LOAD CONNECTED UNLESS

THE ALPHA ?7Dx(77Si$ IS IN THE TRANSMIT CONDITION, IT IS ESSENTIAL

TO USE THE FULL BREAK-IN KEYING CONNECTIONS (Fig. 8) AND TO BE

CERTAIN THAT THE RECEIVER ANTENNA slide switch IS RETURNED TO

NORMAL BEFORE ATTEMPTING EXCITER-ONLY OPERATION. (See Fig. 6.)

ALC - ALC may be used with suitably-equipped exciter/transceivers

t help maintain excitati n at a desired maximum level. A nega

tive -g ing ALC c ntr l v ltage appears at the ALC jack when

amplifier grid current exceeds a preset value determined by adjust

ment f the ALC thresh ld trimmer p tenti meter (l cated near the

t p f the main plug-in circuit b ard, CB2, at the rear f the

p wer supply c mpartment).

This negative-g ing ALC is c mpatible with virtually all p pular

exciter/transceivers using vacuum tube p wer utput stages; s me

newer all-s lid-state transceivers (such as certain Atlas and

Ten-Tec m dels) utilize p sitive-g ing ALC, but als inc rp rate

their wn adjustable-thresh ld internal ALC which is suitable

f r excitati n c ntr l in lieu f amplifier-generated ALC.

In either event, it is necessary that the ALC thresh ld c ntr l

be set t pr vide the desired amplifier plate current meter swing

while the exciter mike gain c ntr l is simultane usly adjusted t

yield the degree f exciter ALC acti n specified by the exciter

manufacturer. The tw adjustments are s mewhat interacting, s

that several iterative readjustements may be necessary t achieve

desired results. EXCESSIVE MIKE GAIN OR ALC SENSITIVITY MAY

RESULT IN VERY LOW POWER OUTPUT, ALC "HANG-UP," AND/OR DISTORTION. ©

Figure 6: Simplified ALPHA 77Dy(77S^ Antenna Switching System

RCVR. A N T S M

-6-

Figure 7» ALPHA 77Dx(77Sd Interconnections for VOX or PTT

R G rS A /U

75 A N T . R G -S 8C /U

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Figure 8»ALPHA 77Dx(77Sd Interc nnecti ns f r CW Break-In r

Fast VOX (Als suitable f r PTT, Manual T/R, etc.) ~

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