Advertisement
REFER TO THE SCHEMATICS AND PARTS LOCATOR IN APPENDIX J.
3: CARD #PS
a)
Measure the voltage across C111 ( or other convenient point on the + 15 Volt
(POWER SUPPLY)
bus) with the DVM. Adjust R106 until the DVM reads + 15.00 Volts.
b)
Measure
the voltage across C112 ( or other convenient point on the - 15 Volt
bus). Make sure that the voltage is between - 14.85 and - 15.15 Volts. If it is not,
refer to Appendix B (CIRCUIT DESCRIPTION), paragraph 8.c for troubleshooting
hints.
BEFORE
ALIGNING
EACH
CARD
AS
DESCRIBED
IN
THE
INSTRUCTIONS
BELOW,
REMOVE
THE
CARD OF
INTEREST FROM ITS
SLOT
AND PLUG THE
EXTENDER
INTO THE EMPTY CARD SLOT. PLUG THE CARD INTO THE CARD
EXTENDER.
THIS
WILL
ALLOW ACCESS TO
THE
ALIGNMENT
TRIMMERS
AND
TEST POINTS.
NOTE:
Cards # 0 and # 1 will
be
aligned
later.
Card # 2 requires
no
alignment.
4: CARDS
# 3
a)
Remove Cards # 3, # 4 and # 5 from their slots. Plug the extender board into
AND #4
the Card # 3 slot. Cards # 3 and # 4 will both be aligned on this extender, one at
a time, without moving it from the Card # 3 slot.
b)
Plug Card # 3 into the extender board.
c)
Connect
one side of a 137K 1% resistor, and one side of a 243K 1% resistor
to
a convenient ground point ( like the chassis) by means of jumper leads. Using
two
more jumper leads, connect the other side of the 137K resistor to the side
of
R333
away from IC305, and connect the other side of the 243K resistor to
the side of R348 away from IC309. These external resistors now force reference
gain- control
currents
into
IC305A
and
IC309A
respectively:
97uA
into
the
"Master" VCA and 55uA into the " Bass" VCA. ( Short clip leads will minimize hum
and noise pickup.)
d)
Connect
the
chassis
ground
of
the
oscillator
and
the
low
side
of
the
oscillator output to the chassis of OPTIMOD-TV. Using a pair of jumper leads,
connect the high side of the oscillator output
to both the "+" input
of IC301A
and the "+" input of IC3018. This provides common- mode excitation for the input
differential amplifier.
e)
Set
the
oscillator
frequency to 60Hz,
and
the oscillator
output
to 0 dBm.
Observe TP1 ( pin D at the card connector) with the AC VTVM adjusted so that
the
common- mode feedthrough is readily observed. Adjust R316 ( CMRR) to null
it. The nulled level of the 60Hz should be less than - 60dBm.
f)
Connect the low side of the oscillator output to the "-" terminal of the left-
channel
audio
input
of
OPTIMOD-TV.
Connect
the high
side
of
the
oscillator
output
to the "+" terminal. Set the oscillator output frequency to lkHz and the
oscillator output level to produce - 15dBm at the output of IC302B ( TP1 or pin D
of the card connector).
Advertisement
