PCB520 Transistor Replacement Instruction
35010 to PCB520 Substitution
(Models 4D3, 3D3, 3250, 4C3, and 3900)
Reference: Use this instruction to install part
PCB520, which is intended as a
direct replacement for part 35010
metal can FET transistor used on
the above models.
Materials Included:
1 - PCB520 assembly
2 - H50606, #6x3/8 Sems
2 - H50608, #6x1/2 Sems
2 - H63093, #6 large flat washers
2 - 90049, 5/16 Hex swage standoffs
2 - 91038, ¼” plastic hole plugs
Tools Needed: Wire cutters, wire strippers,
small flat-bladed screwdriver,
medium Phillips screwdriver.
Warning-Hazardous Voltage
Warning-Internal components may
be damaged by static electricity.
4D3, 3D3 and 3250 Instruction:
1. Turn off the instrument power and discon-
nect the power cord.
2. Remove the intrument cover.
3. Locate transistor Q1B on left-rear of the
chassis. Q1B is the transistor nearest to
the top of the rear panel.
4. Remove the screws securing the protec-
tive black plastic cap on the outside rear
of the instrument.
5. Remove the old transistor and insulating
materials by gently prying with a flat-
bladed screwdriver.
For additional information or technical assistance,
please contact Advanced Instruments Hot-Line
®
Service Center (U.S. 1-800-225-4034, outside North
America +US 1-781-320-9000).
A B
C
D
6. Remove the transistor socket Q1B from
the rear panel and clear the mounting
holes of any remaining hardware.
7. Cut transistor socket Q1B from harness
M20150.
8. Strip wire insulation ¼” on four (4) wires
formerly soldered to the transistor socket.
Twist the stripped ends to prevent fraying.
9. Install the hex standoffs to PCB520 using
#6x3/8 screws, with the flat end of the
standoff against the board.
10. Connect white/red wire to terminal 1 (A).
11. Connect white/brown wire to terminal 2
(B).
12. Connect brown wire to terminal 3 (C).
13. Connect black wire to terminal 4 (D).
14. Install completed assembly inside the unit,
against the rear wall with the terminal
PCP520R Rev0
(4D35/4C35/3255/3905 Service Manual)
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