Kenwood TM 255 E Service Manual

Page 2

TM-255A/E

FREQUENCY CONFIGURATION

me TM-255 uses singte com is: '
receive modes except FM reception. Mil:
is used (F191) ThefrequmcybrSSB
the fdlowlng equaflm wl'm m m:
the nputfleqmflcy (1m) "ammo mu
an SSE! signal with a name: pdntof M 3:

«mm Hula

Snce all these hemendam W '
shown In Figure 2(PLL hepatic)! M '
frequency is determined oriy by the .
fan). and me PLL awe rain mam
Manama fraqumcy comma!»
lug frequency.

The accuracy 01 the m
oscillator (TCXO) used in no I'M-$5 U
+600)

3'

7" lM-MWHz
M'IWHX

TX IX 10.09!!!

A

RX WK ousuuz

LO!

3306435305! IEI
1333fi-37JOSMH: [KM

x i_

\x I,

C Q;-

Page 7

TM-255A/ E

CIRCUIT DESCRIPTION

- m tom-1d

The receive! homend consists ola mstaga hgno band
pass filter. an RF amplifier con-prismg Saks PH 0401
(38K184) threestage band pass filler tuned Mm variable
capacity, and a mm 0402 (39(131(M))am an IF amplifier
ounslstol HIST 0403 (29(210(GR))

The gain is commlled by applying the ABC voltage In the
second gate of 0401 When he AlP slgnal ls on. 0404
(DTC11-zEK) turns on, deems-n9 the AGC voltage and so
reducmg the gain of 0401 to produce the AIP ellem

- AGO drum

In the TM2551heAGC voregels applied as both 040? ol
me RF amplfliei and M05 FETCH ($K131) al the IF amph-
fier The A60 vollage is calmed and amplified by $38
hybnd HIC CZ (KCDm) Snoo the voltage changes in the
posiluve range only aumuabm is not obraned il It is applied
to 0401. which S a (San FET Thus. the AGC voltage is
appled dlreclly lo the second gate of Q! as IF AGO. and
also applied to the second gas of 0401 by convening tle
level wllh the non-lnvening amplihav compnsng. operatlonal
amplifie! 109 (NJMIESBM), so that the voltage changes n
the negauve rangeas well

The tlme constant IS autunamally swltcheo to SLOW for
$3 and FAST to Why 0 27 (25908) (Flg. 5)

AlP)-1

0004
DTCHEK

Fla. 5 Rocdvor tram-om! and AGO circa!

Page 72

TM -255A/ E

72

ADJUSTMENT

A6 S METER CURVE ADJUSTMENT ($9) (ANY MODE EXCEPT FM)

. Adjustment luncflon
rm! me 5 meter voltage was momares 39 :me Hrs! \arge
segment} 11 :xwec varzauons r! the 39 Have: 0' me 3 meta
- Adjus1ment procedure
11:1ut we {cam-33 evenaxwr am
he SC,

2 Fr:s$1"h'-' \C' -JLC\V Ki; 1 "ND NIC Up- DOWN kev

89 beg rs m gm Wm

. Dsplay
On Menu No

. Remarks

The CIA-e betweer ST and $9 mama Den mm the 49149 at
'Ve'ws A5 and A6 my me aopromrnatwwr' The cuxe 'ne'ween
:3 ShCYulS"119 soma ed (r:,\"' the levee, (r: 9an AE and
A? m we acp'oxlmanm he a' bare Jper: , 2009-;
*0 m9 Gwen The mm». It? : Iatea when the
UPUGWN Kev rs oressm Tue dev'a s 127 appvmn
13er y 2 3/ v

.T (JUN-9

H luv 3

On

FLDCK MHz A

we a - -

TONF REV

DROC' ATP

'fipflw

mss CTCSS co
MSCR PRG SCAN -

NB AU'O

TOT

On The vnput ND vaue IS
csplayeo £0 FFm

ATS METER CURVE ADJUSTMENT (FULL SCALE) (ANY MODE EXCEPT FM)

- Adjustment iuncflon

Inpu thee mexe' mirage a: w'uma
rfiee' :gH * r (anectvanatuvr :nefulksm
39:9

3 he segmers 0- tr: [5
be mine

(1,

'l:

. Adjustmem proceduva

1 rpm he snecmed Lave a! \werflw 3340 GB beg ms :9
:gh A. ['I 'le SC

Tm: Curran: Ari) value 10! me 89 \evel swrec
m The mtcmmmpule' Is dtsplayefl 0 H v-h

C1

. Romans

Twe mm? cerw€em am 2 scale Ems-d mm m;-
AB 31C. A? 0/ Inc: apcromal or The 'Teie'
die azccrdmg Tc "1
«,sz led NE NE K 1
scale s 55 ALWWMUEHE-r : YTW

was 0" mews;

715 3mm
THC- deau! Mr 1le

n :u'reV'fiy' m

Dresses

ELY?-

E ,' Te LOCK/LOW POyCthe WC URIDQWN hey
-Dlsplay
On MenuNo
My] FLOCK MH' A we a -+ TONE REV PROC mp NB ALTO
it MCH S m FM
@ * ' Q.
BUSY Drss ctcss co
ON NR MSCR PR6 5cm . TOT

On we moat AD value IS
msauyua (D-FFHv

The cur-zm A D valuu Iorrne Vul scam IeveT s'ored
mine muomfiputcr 5 asphayed {CVFFI h