+
FIG. 2.14 ELECTRONIC TIMER SCHEMATIC
b;,jtl\:.'r~
1l~$1_
Figure
~~
14
presents
the electronic
timcr
schematic.
Operation
of
the timer sfarts
with
the
setting
of
I
he
dial on Ihe camera back which
is
directly
n.:mn<:l.:lcd
to
the
one
megohm
potentiometer
"hown
In
Ihe schcm.uic.
(The
potentiomeIer, in
[urn,
j"
connecled
10
the
g~
microfarad
capacitor.)
Cb:II)~mg
lhe
dial
Selling
aiters
the
value
[or
rt!-
"1\l.tnn'j
of
tilt'
pOlentl()meteL
For
example.
if
Ib\.,
til.11
wefe
s.:!
to
15.
it
would
take
15
seconds
lilT ",'lIrrdH
rJ~ing
Ihroug.h
the
potentiometer
to
dUf}!4"
111\'
tC
tnlt:rof:uad
capadtor.
11l~'
tllm:l~
..:ydc i" imtl:.lh:d
by
the
removal
of
tht;
'.-'\!,pwu
plo..:wrl!"
(Pulhng
Ihe yellow
tab,
from
the
,::,JmcrJ
Till'-
momentarily
doses:J
two~pok.
OOf-
mall;.
()p~'n
"wlleh
JIllJ
completes
the
timing
dr~
tun.
TI1-.:
dosm~
or
one
role
allows the capacitor
10
lull)
tl!:-.dl~T}!e
throtl~h
the
-;'7
ohm resistoL
IIbmIllJ.~
tll:J!
It
ha"
no
resiuuaJ
voha~c
from a pre-
VIOU~
fimmg
cyck.
The
dosin,g
of
the
~econd
puit'
HIm'
til.:
Ie·
trunslstocreslstor
cin:uil
on
and
l!~hh
Ilh:
bmr"
\\'hen
the
"wHeh
orens.
thl:!
g2
mit:roIJr;u.l
cap~..:ltor
begins charg.ing again, While
lIlt'
Lap:J.:llor
l~
charging. tht: lamp remains iilumi-
nated,
Once
the
capacitor
has
fuJly charged, a
difference in potentiai in
the
other
Ie
transistorl
resistor
circuit excites
the
transducer
which emits
a high frequency
"beep",
At
the
same
time,
the
lamp goes
out.
The high frequency
"beep"
coupled with
the
extinguishing
of
the-
lamp
indj~
cales
that
the
timing cycle has been completed,
FLASHGUN
This discussion concerns Hself
only
with the
Model 268 flashgun
used WIth all cameras in
the
fOO,
200.
and
300
lines,
except
for
the
Model
360.
The
e)ectronJc flash used
with
the Model
360
earner
.. is covered in
the-
"Repair
Manual for
the Polaroid Land Camera Model
360"
pubUshed
in
September
1969.*
Early Model
268
nashguns were manufactured
with a
4.5
vdc battery while newer nash guns rely
on
a 1.5
vdc
cell for their
power
source. All 4.5
vd.c
flashguns should be converted
to
1.5 vdc
• lntegt31ed circuit
* Available
only
to
authorized repair stalions..
10
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