Standard Horizon HX400 User manual

i .....................
SERVICE MANUAL
LFB00089134 0001
LFB00089134/1

CONTENTS
TH:~OR¥ OF OP~RAT~O~ ........
41.1
41.2
4,1.3
4,114
41~:i
411~
4,1 ~7
The Rese~ C~-cu~t ..............................................................................................
Extemm sgna~ connections and fnterf~a:~ng
PT"[ and Fro~ Par)e! B,ut~o~ ..................................................
7
S c~a~~b~et C}rcu~t ....................................................................................................
Secondary [}~g:~la~ to A~na~ogue coavmser ........................................................
7
4,2 ! Lo~ ~::ilter.
4,2.2 Th~:~ Trans~fl~ VCO
4,.2.3
~he ~ce~w VCO
4,24
The Trarmmib’Rece~e VCQ
4. z;,.~
VCO Buff:er .Am~lifi:ers ..............................................................................................
9
4.3, R~[. ;EwEA SECRON .............................................................................................................
I0
43 ~
A~~te~’~ L~>,~ >aSS ~}~ter ..........................................................................................
10
4.3,5
Second RF Fil~er ..............................................................................................
11
4.3 5
MrX~:~;~ C#cu.~t
~}{sl !~~ Rmp
Second ~: Circ:u~it ~Oemodula~or
Second }[~ F:~ter
4.3.10
bt~te (~Jr,;~#~ ...................................................................................................
4~3~11
Audio Proces:~r Circuit
4=&12
Sc~a.mb~ed
4.3,13
Mu~e ~nd
442
Trs~nsm:~
4.4.3
Tr~nsm£ Au~fio ~x)oess~n9 Circu~ ...........................................................................
13
4,4.4
~ra~’~s:rY~
4,4.5.
VCO cbcu~
44.6
Lo~v Po~er
4,~6.1
Bstteq,~ ¢on~ec.t~:ons and Protect~o~
Pag÷ 2of 4i
LFB00089134 0002
LFB00089134/2

5., ~ISASSE.~SLY ...............................
~..3.
R E M(]VI N G TH I;;. A U ~3K3;~© ~SPI..~sY BO,o%;R D .................................................................. 1~5
T, I. HX420 VHF R/{o:lo PAr~ L~s’r ............................................................. 1~
72. 4XSS0 UHF RADIO PA£rS ~.,~;t ..............
24
72,1 Audio£Xsp~a~ Board ..............................................................................................
24
?.2.2 Mahs Board ........................................................
~r~r~ ~oohma~ aot d~e~e&
PARTS
9,1
HX420 V~4F RADIO C ~iCU~T Db~s£S~A~’~ ................................
32
HX480 UHF I"<,/,@~O CiRCUFr [)~AGRAM ...........................................................
33
10.1 ItX420 VHF RAOIO COMPO~N¢:NT IL,~YO~J:TS .............................................................
10, I, 1
HX420 VH;F Control Bo a rSi Top Pa ~ts Compone~1~ La ¢oul ...............................
34
t 0. t .2
H£4,20 VH~:: Cont~’o/Board~ Botto~l PaRs
!0,t,3
HX4,20 VHF RF Board Top Parts Cosspdnent
10, ~ ,4
~qX420 VH~ RF Board Bottom Par~s Com#o~e~t Layou~ .................................
:,!7
10.2.1
Hx480 UHF Oon~ro~ :Board Too Pa~ts CamE~onsnt LaTout .......................
38
I0 2~3,
HX480 UH:F RF Board Top Psr~s C0ntDonen~
f0.2A
HX42~0 [..~H~F RF Board Bo~o~} Pads Coms~nent
FIGURES
F~gL~re 4,24 Syntt~es~zer B!gc, k Diagram .........................................................
F~gure 4~3..I Rece~ve~ B~ock D~agram .......................................................................
F~gu.re 4,4-~ Tra~sm~te~ B~ock Di~sgram .........................................................
LFB00089134 0003
LFB00089134/3

lhe ENTBL HX400 series is ~ PMR haadh@d twa~way VHF.iLJ~NF ~ransceival.
el Ultra camsact s~ze and deanna, ~t :~s made o~a heew du~. commercial
It is canstr(4c~ed with a m~c~’ep~{scesso~ con~relled temperatu~-e compensal:ed
Pha se LocKed Loop(PLL} croquette}, s~nt~es~zet Th~s #me~ the capabllbCy of
256 PC progra;mmable channels.
CTCSS & DCS
Most e[ t:be receP~m9 pa~s are swi~cbed off ee-riod~ca~y m ~e p~’war save
node to red~ce ba~e9 carre~t d~ak~ dudng slandby.
The t~ansce~ve~ includes ¢he fo4158wM9
¯
p~og ~ammab~e
~
2/5 tone sel~ca~
.. Lo:ne WL~rke.r
~
Stun sad Unsttm Feature
~
B.u~! b4n Scrar ~b~ef
-
M~ssed call faci~tV
~
Emer~eacy Call feature
~
VOX [~o-lce operated transmit with auto
~
easy~to-read LCD
The batte~ uses L:lth~um-~on te,ohno~ogy,, which g~ves a 1~ ~sour d{.£y Oyc~e
The Ba~e~ ~ system slse has a batteH leve~ me%ajar, a low baUScH wara~ng
~b~eep.
The t~ansCeive~" aiso ~as= an e×tensive range of accessories;
2:1,
!~e [~ .................................................................................................................... m°P~: M °~e! ..............
?~’~T’T" ~T": ’i=~:~=’=! ,.. ~:{~2~!.! ~ ............... ......
Radie
~:, HT420 (VHF)Or i
Antenn~ .............................................................
!~O0mAh L~ ~0n ba~ter~
~.~Hng Leaded Rear Cii~,
LFB00089134 0004
LFB00089134/4

The blX40O .Series is suppoded by s wide raoge of’ ~seful’ access,er~es
For an ,up to date ~st visit our web site at’. www,enleLco.,uk
LFB00089134 0005
LFB00089134/5

describe the circuit ®pe.~’atio~ ,el ~he ~adie; tae desc~iptiel~ !~a.s been
2~ The Sy~hesizer section
3, The ~eceiver section.
~he ma~n rn~croprocesss.ro has seve~el a:r~eilla@’ eompo,nea~s, which assist it in
~s operation. Th÷y ate ~esc=.ribed i~ the following..} sec~}ons.
t’his c~ ~ (U805) holds (he remai~sing pa4 of ,~he soRwa~’~s for the
Mio~oprecessor. The ROM communicates w~tls the Micro~’ocesso~ by ~sir~9 ~s
4.!~2. The L~D Drive
Three L.[ID’s are driven by 3 of the dig~ta outputs from the Mic:roprecesso~
One drives the Red EE©, one ddves the Green~ LeD and o~se drwes the
b~:~c~k~i!~ht [.,.ED’s t4 conr~ected
The M cro<>roces~.or requires a reset ¢ircu.it for correct ~ower up
operatio~ ’RI~s ~s ~rovided by
LFB00089134 0006
LFB00089134/6

The PTT button (8W608.)is iqterfasoed to,Be Microprocessor di~’ectl~, via U801
80, A!! o~ber buttons ose:nste ~h~ough a resistance vakse aath switchers9 systam. Th~s
ope~’ates b~, measu:nng the vo~t;~ge on a po~a~ whe~e the volb~ge ~s eeper~dant
which switch is ~sct~va~(ed, Th~ ~de~t~fies which o~ the various sw~tches are achvated
qh~ sw~ch.es are 8W801 to 8W8.07 :n~c:~us~ve. an:d 8W80~
LFB00089134 0007
LFB00089134/7

The s~nttses~.ze¢ spe~a{®s by ims.lementi~sg tae p[~Ise swallowing reel:had,
using the, btoc~k diagram ~iv÷n i,n F :gure 4;2,q below.
mod:t~lat~os ol the Refe~-ence Osc~a~gi-’ (TCXO}, "Cb~s permits modulation at
requwe an extreme y low frequency medL~at~on of the VOO
The I,oop fi~ter takes ihe variabie p#!Se w:idth ou~pu¢ from the Phase
Page8 of 4I
LFBO0089134 0008
LFB00089134/8

The tfansmi~ VCO w~tn c~mpone~l(s art}uF~d Q405 [ak.es ~t]~e ~oop :Nter output
as the ~s~ain #equenc~ cont~ol ~n~ut, but aBo has b~7o other frequenc~ con~rc
~~od[s These are ~he Speech (MOD AU~3~O)~nPuL arid the MOD TONE
a~alo }npuL These tater 2 ~np8~s con¢re: the freqLae~soy e~ the VCO by
c~’~amg~g the, voRage across a common vat,cap ~Siode D403 The ma~n
~reqqe~cy aput controls the frequency of the VCO by changu:ng the voltage
across a vancap d’4odes D404 ~nd [3405
The MO©...oTONE signal is also conr~ected to }he Reference. Osciita£or
(TCXO}~ to provide the c~oss point modu~a~o~ capability. Refe~ ~o= the
l:rsns~’~~it Sect@~ ~or fl.idher deta~ils.
The Receh~e VCO
The rececve VCO takes the same =.ooo ~}.ter output, as .....
the ors:y, frequ~ncy. ,. ~
contro in~u~ a~d cor~trols Ihe ~req~ency o~ t~.e VCO by cna~~g~g th~ Voltage
across a var~ca~ @ode :netwOrR O48!. an~8 D402 T ~ "
,
.
~he ,7CO operates u~s~ag
t~ans~:stor Q4O 1
The TransmWRecei~ve VCO P 3~er Swi~chin9 CirC[,.~@l sets oower on to the
Transmit VCO dudr~g Transmit an~ the Rec~ve VCO durir~g rece~v~. The
ir@~l-~ ~o th~s ci~rcwt ~s the TX/RX IoMc contR)~ ~l~i~e. Th~s ~(~g~c s~al swKches
Q406 to ~rov~d@ power ~o ether oi ~he 2 VCO’s
s~o~nd Q402 asd Q4O&
LFB00089134 0009
LFB00089134/9

F~g~8 4,3-1 Receiver Block D.iag~am
4.S.1. A~te~na }Low pass
Receiyed si!~na{s fr:o~’ pass t£w.ough [he co~snector (CON201} a~d are passed
to the an{e~na switching c~rcu~
4.3..2o Ar~;e#~a Tra~smidReceive switc~i#~ c~x;~it,
Th~s Transm~b’Rece#/e sw~tc~: is co¢-~tro~ed by ~he TXEN_SV s~9na~ m
recerwng d~Od,e D202 [o D205. are ~umed off. which isolates the antenna from
the~ra~smcter c~-c~J " "’ .......
sw:~ched oh wh~c~ gro~)ds ou~ the Rec@ve :}r~ou~, .a~d connects t’n:e
F~rst R~F F:llter
r~ext stage Is the first RF ~itt:~r. which has a, pass ba~d co~’~t~x~lled .b~ ~he
the RDAC ~igna :l"h~s fiatet al.~o ~a~ a s@na~ ~s~er L~S~ng Dt03
The ~qex[ :stage s the first R~~ ,Amotifier based aroused QI01_ The ©C ~,ower
for i:h~s stag¢~ ~=.s f~ ~’ovided from RX....SV
Page i 0~8~ 4’1
LFB00089134 0010
LFB00089134/10

The next stage is tl~e dua~l gate FE~ ~ixer. The Receb~ed ~d amplified RF
SeCO17d ~ate.
[~e ~e×t seve{al sta~es .ar~ c:on[ain.ed ~n ~he FM O~;[~o,d#~to~ ch p, u!0!
This contains t~he secured tF m~xe~, whefe the fi~st tF and second LO ,t~rem the
RX 8..oer~d LO Tri::~ler} are mixed to produce a 455 kHz :second IF signal.
This circuit is entire 7 co~t.ained inside I0581.
PaSSeS thorough p~n 5 of U10! and ~s applied to a cef~am~c fil~er FLSO2 and
This circuit ~s entiret’,/. eor}t:ained r~s.ide 10501
Here ~a~e second F sig]qa~ s fed [oa guae~oa~ure det÷¢to~ (X!011 wm:s~e ~[ ,s
co~wer,t.ed to audio asd o.Jtp~t tl~om ~ia 9.
LFB00089134 0011
LFB00089134/11

The d e:n"~(x:~.~{ed
MiUTE c~s~:rOI ~o the Audi~o Processor c~cu~
4.3.12~ S¢~amble¢¢ Desc.ra~bler Ct~ip
To~e at~d~c s~gnal ~s tbe~r~ ted through ~he Sctamb~edDescrambter ctlip to
remove the s;c:ramblir~g. The ScramSler input :~s p~£~ s 1 a~sd the de:~.~cra:mbled
4~3,13,
and Vo!~a~e Audio
~he de~ected audio signals a/’e ted threugh a logic con~roiIed swi~ch (Q6~02)~ ¢a
th~ Vott~me control Th[is a~.ts..~s a potential d~vldet whet~ tt~e i~]#~t s~]a s
~de~tif~ed~ as VOL.....AUD~#q. afld the e~t!pu~ s gna ~s VO/_AU:D_O=.tJT
I~he a~dio signal leveJ t~en }~#ut to pin 7 of f;he AF powe~ amp~f~e~ U808.
Tn.e amplified sig ~a s ou~pu~ #ore pin 3 of U808 sad ~s passed to the
~ntemal speaker SPED!. A ~e~c:.oRd aL~d~o ~np~t ~O th~s smp~i:~er ~s the ’IX
BEEP signal Th~s i:s 9eaera~e8 by the Processor and ~, ~ed d~(~c~ls ~o lhI~S
Par,.~(~ i2 of 4=t
LFB00089134 0012
LFB00089134/12

Figure 434 below,
44ol Trar~smi~ter B!ock Diagram
7h~ mlero#ho~e withir [he B~iereplq:o~e assembly MtC601 ~s amplified~ by an
]-he s~>eech s~anal the~ oasses ~hrough U604, which ac~s as a MUTE
sw~tca~mg cow, fro} of the Speech s.i.~na~
~°his s~gnal ~s thet~ ~ed to Lhe Audio Pr’ecess~ng Ch~p U602 P~n 17, The output
of ~his chip ~s ~m 23, ~Thich feeds ~o ttwee s~ages ofop-amps (U303C~ A ~nd
th® MO©_TONE signa~ is a~so con~°}ected ¢0- ~he aew freq~4ency path [o. the
Refel~nce Osoilla[or ~[CXO~ used to !~ ire the-19w frequency ~,efos;s poinb
via VR:~01 ~o [~se %~OD inpu( of the TCXO
4,4:& VCO cir¢#i~
The transmit modL~lahO~ Circuit has already been described :Jr~ the Sy~]~nes~zer
4.&& Low Power Tra~smit Amplifiers
Th.~:~ m0d~la~,ed ttar4sm]l si#~=~a-~l is applied ~o t~e. buffer ampl#~e~ baeed a~ound
Q206
1the amplified signat is sp@lied to a sec©~]d su~ffer ar~ slifier based around
Q202, These 2 amp~i~ie~ st~@~:s =~ntr:ease t~e s~s:al level from around i mW
~o 50 roW.
LFB00089134 0013
LFB00089134/13

signa! powe~~ is ~sr(he~’ irsc~reased to a:roursd 500row in the ©~iwr amsiilfier
based a~’o~:d Q203, The g a:[~ o~ th}s stage iS dependen~ on (he bias,
The ©C
’l"l’~e ~°.~ower fe.~ ~a~s s~age ~s provided fto~s tt~e Ba[t:~sry via the fuse a~tld [he ;>A
cur:ren~ ee~ec[~.oc circu~L This ourre~t detect~o~ c~rc~t measu~-~s the current
Pa!~e ~4 of 4’I
LFB00089134 0014
LFB00089134/14

The ms~m pows~ ~eed ~o the :rest of the radie comes ~rom ~he Positive 8ows~
tem~i~sa~ ~ON:503. aCid con~=~ec~s t:=h~-ough the O~iO~F sw~ch b~.~iit islo the
Vol~,~me ¢or~troL -f°he tsext ci~cul~ sect!ons is a ver’~ !ew dro~s-eut regu:Iator chi~
((.JSOl :!= which orod~.~ces the main +Sv su~#p!y #or ~h÷ i"adio la~s:el~ed R.F_5\L
[he ~ext oower ~af,~e takes the BF_SV vol~age and splits it to two
wh~c!~ ~ 1urn, control ~,he ’TX_SV ssp~, an(S the RX_fV supply,
comgone~sts based around O50I aria Q502
Du~ing T~ansmit the TX_~V vo}ta98 is set to 4.8V. arid (he RX ~SV Vol~a~}e ~.s
powe~s,,s ofL Duri~g Reoeive the. TX~SV voltage ~s d~owered off ar~@ the
~? 5V vot~as:e ~s se~ to 4.8V. These sre con~ro~ed by ~he CP~ TX and
GPLJ......~:~X signals coming ~,rom the Microosrocessor.
Pag÷ ~li 5; of 4 !
LFB00089134 0015
LFB00089134/15

Instructions for attaching# and remov~9 ~he B a~e~’ ~ack a~e g~v~n i~ the
radio. (undo r batt~sry w~~en f!tted~
#ove~ (on e~de of ~.a@o oppo~}te ~o PTT), R:~ov e con r~ect.o~: cove~:
3. Remo~e 1 offTORX 8 screw from p~ate, ho~d~g speaherh~c~ophene. Remove
8sOrt sma~ fia~: :.b~ade screwdriver ~nto ~ecess in ext~eme d~t.-hasd comer o{
Ge~iy irss8 rt small fl~ b~ade scsrewddw~ b~tweea top o~ chassis and p~as~c
radio cove: Gen#y ~ever up~o free main chassis:
Ren~ove main chass~& This then gives access to Audb~’~Disp~a2 board, and
Main board
2 Remove ’~he Volume cont~rel sl0t~ed ro~r~ nut from the ~op panel o~ the radio by
rota~9 the bckin9 dn9 ;recesses using: a:n approp~aet too~
4. Rsmove ~he 6 off Pos~dir~ve screws #0m ~he Main boatd~
Pa{~e i6 of 4!
LFB00089134 0016
LFB00089134/16

LFBO0089134 0017
LFB00089134/17

LFBO0089134 0018
LFB00089134/18

Q60S Q1
!
~504 G806
l~.~s~; .................................................................
LFB00089134 0019
LFB00089134/19

Page 20 o~ 4!
LFBO0089134 0020
LFB00089134/20