Maintenance—2205 Service
Mains Input Circuit Board
The Mains Input circuit board can be removed
and reinstalled as follows:
1. Perform steps 1 and 2 of the Power Trans
former procedure.
2. Unsolder W903, a three wire ribbon from
Mains Input circuit board.
3. Remove the POWER knob shaft by inserting a
scribe (or similar tool) in the notch between the end
of the knob shaft and the end of the Power switch
shaft and gentry pry the connection apart. Pull the
ROWER knob shaft out through the front panel.
4. Remove the two screws and nuts that secure
the power cord receptacle to the rear chassis.
5. Remove the grounding screw and nut (top
corner) that secure the Mains Input circuit board to
the inner chassis.
6. Pull the Mains Input circuit board and
attached shield towards the inner chassis and up out
of the instrument.
To reinstall the Mains Input circuit board, perform
the reverse of the preceding steps.
Timebase/Attenuator Circuit Board
Assembly
The Timebase/Attenuator circuit board assembly
can be removed and reinstalled as follows:
1. Place the instrument on its side (CRT down)
and unsolder the following wire straps and resistors,
noting their locations for reinstaltation reference:
a. Unsolder the two resistors from the CH 1
VOLTS/DIV and CH 2 VOLTS/DIV switches to the
Front-Panel circuit board.
b. Unsolder the wire strap to the CH 1 OR X
connector ground lug from the Timebase/
Attenuator circuit board wire strap.
c. Unsolder the wire strap to the CH 2 on Y
connector ground lug from the Timebase/
Attenuator circuit board wire strap.
d. Unsolder and pull the two wire straps from
the Front-Panel circuit board that comes from
the Attenuator circuit board.
2. Place the instrument down (normal position)
and use a 1/16-inch hex wrench to loosen the set
screws on the CH 1 VOLTS/DIV, CH 2 VOLTS/DIV,
and SEC/DIV Variable knobs.
3. Remove CH 1 VOLTS/DIV, CH 2 VOLTS/DIV.
and SEC/DIV Variable knobs and switch knobs from
the instrument.
4. Disconnect the following cables from the
Timebase/Attenuator circuit board assembly, noting
their locations for reinstallation reference:
a. J90, a six-wire cable located at the rear
edge of the circuit board.
b. J755, a four-wire cable located at the rear
right-hand corner of the circuit board.
c. J30, a four-wire cable located to the left of
the CH 1 attenuator switch.
d. J80, a four-wire cable located between
the CH 1 and CH 2 attenuator switches.
e. J7, a six-wire cable located between the
CH 2 attenuator switch and the SEC/DIV switch.
f. J701, a six-wire cable located at the front
right-hand corner of the circuit board.
5. Remove the following three screws that
secure the Timebase/Attenuator circuit board to the
post spacers.
a. One screw from the right-rear corner of
the Timebase/Attenuator circuit board assembly.
b. Two screws from the extreme left side of
the Timebase/Attenuator circuit board assembly.
6. Remove the Focus knob shaft by pulling the
shaft with one hand towards the front while holding
the Focus pot shaft with the other hand.
7. Pull the Timebase/Attenuator circuit assem
bly board straight back from the front of the instru
ment until the attenuator switches are clear of the
Front-Panel circuit board. Then lift out the entire as
sembly through the top of the instrument.
NOTE
If accessibility to the bottom of the Timebase!
Attenuator circuit board is desired perform
steps 8 through 10.
6--15
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