Infinity Kappa 255A, Service Manual

Page: 11 / 46

Infinity Systems, Inc. 250 Crossways Park Drive, Woodbury, New York 11797 (516) 496-3400
Service Bulletin
Service bulletin INF9701 Rev1 - August 2001 This is considered a Major repair
To: All Infinity Service Centers
Models: Kappa 255a
Subject: Damaged Output Transistors
When the voltage from an automotive battery powering the Kappa 255a dips repeatedly dips below 8 volts, the
class D regulator can become unstable. As result, excessive current flow can damage output transistors
Q10,11,12,13 in the subwoofer section.
In the event you receive a Kappa 255a for any servicing reason, perform the modification as shown
below. Affected units will have an “HC” in the prefix in a white serial # label (bottom of the unit).
Note: Many components in this product, including two due for replacement, are S urface M ount D evices.
Procedure:
1) Remove the (24) 9/64” allen screws from both lower sides of the chassis.
2) Remove the (2) #10 Torx screws from the bottom chassis underneath the tamper-proof labels.
3) Turn amplifier vertically and strike on a hard surface, dislodging the main PCB; slide entire assembly out of
the chassis.
4) Remove and replace any defective
IRFS250
output transistors. (Q10-13 are Infinity part# TR1238)
5) Change R3 on the Digital Predriver Module (PC1207) from 22k
W
to 2.2k
W
(Infinity part# RS1703). PC1207
is the small upright board located near the main PCB filter capacitors. R3 is on the component side of the
board facing the outside of the amplifier. See Figure 1.
6) Change R15 on PWM Module (PC1149) from 1k
W
to 2.2k
W W
(Infinity part# RS1703). PC1149 is the small
upright board located near the main power supply transformers. R15 is on the component side of the board
facing the inside of the amplifier. See Figure 2.
7) Reinsert main PCB into chassis; confirm that all (20) insulators are still in place, attached with heat sink
compound to each output device.
8) Insert and tighten all (24) chassis screws, including the (2) Torx screws on the bottom of the unit. Note: the
(4) shorter, 5/8” screws are inserted at the ends of the amp chassis.
9) Attach all power, speaker and signal cables to amplifier and test.
Model Serial number Status Action
KAPPA 255a “HC” in the prefix
below -01701
Damaged Q10,11,12 or 13 Change R3 & R15
to 2.2k W
KAPPA 255a “HC” in the prefix
-01701and above
Modified by factory NONE REQUIRED