Heathkit GR-78 - Page 36

CONVERSION OSCILLATOR
‘Transtr Q411 and is asocloed crcl form the 3.670.
|Wizhetaradye eciltr, which i used to provide doubie
omverson on Band F ony, Injection voltage ' couplad
‘trough enpctor C407 gate 2 of O401 which is opratad
8a micron Band F only.
ANL
‘The detected sudlo fe connected trom the ANLC/SSE
‘itch to the AF Gain contol SO5 by one of two path
pending upon the postion of ANL fautomac oi
lite) steh SWEDE, When the ANL sith sin the OFF
oitin, the aud slg e outed through eapucitor CABG
Yo eapecitor 0439 which I connaet to the AF Gain
‘control. When the ANL sch ls inthe ANL positon, dhe
‘uti sgl: routed through the automat noe miter
‘out inst of eapaitor C436,
‘he detected ud sna i prveri rom Hing Heough
essors RAMS and RAAG, Thane two restos, along with
‘eapaitor £438, form an audlo fier that stops the slo
sigal but allots a sal DC voltage to pat though, This
small DC voltage bless the cathode of lode 0402, The
‘uti sg than pases tv ough resistor AMA, lode D402,
td capacitor CAI9 to AF GAIN contol REDE, The dots
lips the peaks of the ao sgl, tus tig roi pas.
AUDIO AMPLIFIER,
‘The adulo siga trom AF Gain contol REOS is coupled
hvough captor CAAT tothe baw of sudo preamplifier
trasistor 406, Resstrs W440 and RAST form a voltage
‘ividar to provide the creer bist to 0806, DC oparating
bia obtained from the RCV/STBY switch though restr
R449, The aio output om CAB i developed aerox the
ond raitor RASH and direct coup Yo the wecondwuslo
‘hive vara 407,
The output of O07 is avo direct coupled tothe audio
output wansitoe O40H and C409, which operate as 8
complementary par. Blas yoltag forthe output tawions
‘8 obained fom restore RASH wx RABE. Adio output
coupled fom the etter ritrs 487 ae R45 trough
puelor CA46 tothe Yoh panko Haadpono jc, A
portion of the output Is fol bach to the omiter of
roomier QA08 through restr RAB end capaci
(4 to id sblzton and minimie darn
CRYSTAL CALIBRATOR
‘rari 0472, extol, ond the sacloted eeutry
{orm a 600 KHs elation oallatr which ested on
bythe front pel Cal site, SMSOA. Thin BOO kHe
‘lator provides secrete calration markings evry 500
ie fora ealtation.
CHARGING CIRCUIT
The tutary Is actrcaly dvd in lf for charging from
AG,
When
tha
AC
power
cord
ipluaped
int
a
power
out,
the AC vltage from the socondory of transformer TET i
sppliad through diode DBOY on oneal eye to carge
‘no halo the batery. On the other haf yal th voltage is
‘pled tough diode D802 to charge the other hal ofthe
‘tery.
“The batery can ao be charged from 12 t0 15 VOC. When
the DC power cord is comeeted tom power source the OC
voltage Is wpplat trough diode D609, plot timp PL02,
‘ud rsinor ROS to the batury. The de protects the
battery fom blog dichared in cate the external DC
‘chrging voltage connect bckwards, The pilot lap and
restr function primarily ats OC charging curent ite,
‘Te lamp may not nacesaiy be it