Infinity Kappa 255-A Service manual

Kappa 255a

Automotive Amplifier

SERVICE MANUAL

Infinity Systems Incorporated

250 Crossways Park Dr.

Woodbury, New York 11797

Rev2 10/2004

Kappa 255a

- CONTENTS -

SPECIFICATIONS ……..…………………………………………………………..2 FEATURES ..……………………………….……………….……………….…...…3 APPLICATIONS (SET-UP GUIDE) ………………..……..……………………….4

PRECAUTION AND NOTES..…..………………….….…………………………..6 INSTALLATION ….………..…………..…………….……………………………..7 TROUBLESHOOTING ….………..………………….……………………………..9 SERVICE BULLETIN #INF9701 ….…………...…………………..……………..10 SERVICE BULLETIN #INF2001-02 ….…………………………………………..11 EXPLODED VIEW….………..…………………………………………………….13 PCB DRAWINGS ….………..……………………………………………………..14 BLOCK DIAGRAMS………...……………….……………….…………..….…….20 ELECTRICAL PARTS LIST ..……………….……………….…………..….…….22 SEMICONDUCTOR PINOUTS………………..……..…………………..……….30 SCHEMATICS …………..……………………..…….…….….………..………….31

REVISIONS ……………..……………………..…….…….….………..………….43

Occasional refinements may be made to existing products without notice but will always meet or exceed original specifications unless otherwise stated

1

Kappa 255a

KAPPA 255A SPECIFICATIONS

POWER
4 OHM		4 x 50 and 1 x 200 watts
2 OHM		4 x 75 and 1 x 300 watts
BRIDGE 4 OHM		2 x 150 and 1 x 200 watts
1 OHM STABLE		PROTECTION
FREQUENCY RESPONSE		20-20KHz (+0 -3dB)
EQUALIZATION		SEE CHART BELOW
FIXED AT 40Hz Q=1 +11dB
CROSSOVER
FLAT/LOW/HIGH PASS SWITCH		2
DECADE SWITCH		(40-320 & 250-2KHz)
VAR. CONTROL		2
SLOPE		12
INPUT SENSITIVITY		250 mV ~ 9 V
FULL DIFFERENTIAL INPUT		>100K IMP
POWER FUSE		40A X 2 (ATC)
THD + NOISE
4 ohm		0.05%
2 ohm		0.10%
bridge 4 ohm		0.10%
SIGNAL TO NOISE		>95dB (A Weighted Referenced to Full Power)
CHANNEL SEPARATION		>50dB (100 TO 20KHz)
DAMPING FACTOR		>204
TURN ON TIME		3 SEC
DC OFFSET		<50 mv
OPERATING VOLTAGE		10 -16vdc
REMOTE ON CURRENT		<2ma
QUIESCENT CURRENT		<2.5 AMP
MAX CURRENT		80
PROTECTION auto reset
spkr short		Yes
spkr to ground		Yes
thermal		Yes
over voltage		18vdc
under voltage		8vdc
DIMENSIONS		23 x 2 3 /16 x 8 1 /2 in. (W x H x L)
		584.2 x 55.6 x 215.9 mm

All tests to be done from 20 to 20KHz at 14.4 VDC into 4 ohm loads, unless otherwise specified.

Infinity continually strives to update and improve existing products, as well as create new ones. The specifications and construction details in this and related Infinity publications are therefore subject to change without notice.

2

Kappa 255a

FEATURES

The Kappa 255a is a 5-channel power amplifier that offers full-range stereo and bridged-mono operation on four analog channels and band-limited mono operation on a class-D channel for subwoofer applications. The front/rear amplifiers are rated at 50 watts (rms) per channel into a 4-ohm load, while the subwoofer channel is rated at 200 watts (rms) into a 4-ohm load. In bridged-mono configurations, front and rear amplifiers can deliver up to 150 watts (rms) for the same load.

2-ohm operation, rated at 75 watts (rms) per channel for front and rear channels and 300 watts (rms) for the subwoofer channel

Bridge/stereo switches for fast system setup

Built-in 12 dB-per-octave electronic crossovers, variable from 32 to 320 Hz, with an “x15” front-channel switch (to increase the frequency range from 480 Hz to 4.8 kHz)

Dynamic Bass Optimizer™ (DBO) 12 dB-per-octave subsonic filter with variable frequency (20 to 80 Hz) and Q for enhancing subwoofer low frequencies while conserving amplifier power

Front and rear channels, individually selectable as highpass, low-pass, or through-pass

External switch for subwoofer inputs allows direct connection to source units with subwoofer outputs

Amplifier input sensitivity controls to match a wide range of input signal levels from 250 mV to 9 V

Five protection levels guard against over-voltage, undervoltage, over-power, overtemperature, and over-current situations

2-color LED array indicates green when power is on and orange when protection is activated

Industrial-grade, gold-plated, “pre-wire and plug-in” connectors for an easy-to-install highquality interface

Transparent control cover to deter tampering yet provide a clear view of installation settings

Built-in automotive type fuses to protect the amplifier

Unibloc™ chassis provides improved heat-sink capacity and exceptional RFI shielding characteristics

3

Kappa 255a

A P P L I C A T I O N S

Enclosed are several diagrams to help you plan your own system installation. Figures 1 through 3 (on pages 4 and 5) show how to configure the Kappa 255a to drive front and rear speakers and a subwoofer, tweeters and midrange speakers and a pair of subwoofers, and a tweeter/midrange component set, midbass speakers, and a subwoofer.

Figure 1. This wiring diagram shows a Kappa 255a amplifier driving front and rear pairs of full-range speakers and a single subwoofer.

Set Switches As Shown

(set controls for your system plan)

x15	FRONT
	C		9V	G
				A
x1	R
				I
	O
	S		.25V	N
	S
32Hz	O			32Hz
	V		M
	E	BR
320Hz	R		O	320Hz
	O	ST	D
LP			E	LP
	U
HP	T			HP
FLAT	P			FLAT
	U
	T

	REAR				SUBWOOFER
C		9V		G	9V	G
				A		A
R
				I		I
O		.25V			.25V
S				N		N
S					20Hz
O
V		M	D	FREQ
E	BR
R		O			80Hz
O ST		D	B
					MIN
		E
U			O		Q
T
P
U					MAX
T			INT			SUB
			EXT			INPUT
			X		32Hz
			O			60
			V
			E			Hz
			R	320Hz
			EXT			REAR
		FRONT LP				INPUT

Set to EXT for source unit with subwoofer outputs

KAPPA 255a

(top panel)

Figure 2. This wiring diagram shows a Kappa 255a amplifier driving a pair of tweeters, a pair of midrange speakers, and a pair of subwoofers (4 Ω minimum).

Set Switches As Shown

(set controls for your system plan)

x15	FRONT					REAR				SUBWOOFER
	C		9V	G	C		9V		G	9V	G
				A					A		A
x1	R				R
				I					I		I
	O				O
	S		.25V	N	S		.25V		N	.25V	N
32Hz	S			32Hz	S					20Hz
	O				O
	V		M		V		M		FREQ
	E	BR			E	BR		D
320Hz	R		O	320Hz	R		O	B		80Hz
	O	ST	D		O	ST	D
LP			E	LP			E			MIN
	U				U			O		Q
HP	T			HP	T
FLAT	P			FLAT	P
	U				U					MAX
	T				T			INT			SUB
								EXT			INPUT
								X		32Hz
								O			60
								V
								E	320Hz		Hz
								R
								EXT			REAR
							FRONT LP				INPUT

KAPPA 255a

(top panel)

Set to EXT for source unit with subwoofer outputs

FRONT LP creates bandpass when rear output is set to HP

For system expansion, see Figure 4 on the next page.

NOTE: For simplicity, Figures 1 through 4 do not show power, remote, and input connections.

– R +– + L – – R + + L –

KAPPA 255a	-	-
(front panel)	RF	LR
	+	+
	+	+
	LF	RR
	-	-

KAPPA 255a

(rear panel)

REM – R +

+ L –

SUBWOOFER 1 and 2
are common outputs			+		-
and are supplied as
a convenience for
dual-subwoofer
applications

Subwoofer

– R +– + L – – R + + L –

KAPPA 255a	RF		-	LR
(front panel)
	Tweeter		+	Mid
	LF	+	+	RR
	Tweeter -		-	Mid

REM – R +

+ L –

	KAPPA 255a	-	-
	(rear panel)
		+	+
		Subwoofer	Subwoofer
		(4 Ω min.)	(4 Ω min.)

4

Kappa 255a

A P P L I C A T I O N S ( c o n t i n u e d )

Figure 3. This wiring diagram shows a

Kappa 255a amplifier driving a front

set of tweeter/midrange components, a

rear pair of midbass speakers, and a

single subwoofer.

– R +– + L – – R + + L –

Set Switches As Shown

KAPPA 255a

(set controls for your system plan)

R

-

-

(front panel)

FRONT

REAR

SUBWOOFER

Plate

+

+

x15

9V

G

G

C

C

9V

9V

G

A

A

A

x1

R

R

I

I

I

O

.25V

O

.25V

.25V

S

N

S

N

N

32Hz

S

32Hz

S

20Hz

L

+

+

O

O

V

M

V

M

FREQ

320Hz

E

BR

E BR

D

Plate

-

-

R

D 320Hz

R

D

B

80Hz

O

O

LP

O

ST

E

LP

O ST

E

MIN

U

U

O

Q

HP

T

HP

T

FLAT

P

FLAT

P

MAX

U

U

Set to EXT for

T

T

INT

SUB

source unit with

EXT

INPUT

subwoofer outputs

X

32Hz

O

60

REM

– R +

+ L –

V

E

320Hz

Hz

R

FRONT LP creates

EXT

REAR

bandpass when rear

FRONT LP

INPUT

output is set to HP

KAPPA 255a							KAPPA 255a	SUBWOOFER 1 and 2
(top panel)							(rear panel)	are common outputs	+	-
								and are supplied as
								a convenience for
								dual-subwoofer
S Y S T E M E X P A N S I O N								applications
									Subwoofer
Figure 4. In this expanded							KAPPA 52a
system, a Kappa 52a
drives a front pair of
tweeters. The 52a’s low-		Front L/R Inputs
pass outputs feed a Kappa	(from Source Unit)								To Front L/R
255a to drive stereo pairs
							L/R Outputs		Tweeters
of midrange and midbass
							(Low-Pass)
speakers. An external
subwoofer signal feeds the
Kappa 255a to drive the
subwoofer(s). Another
Kappa 52a drives a rear							KAPPA 255a
pair of speakers from the
source unit’s rear outputs.							Front L/R Inputs
Subwoofer Inputs										50w x 4 + 200W x 1
										2 5 5 a
(from Source Unit)
			FRONT			REAR
		x15	C				BR
			R
		x1	O		LP	O	ST
			S			U
			S		HP	T
			O
			V		FLAT	P
				BR		U
			E			T	To Subwoofer(s)
			R
		LP	O	ST
			U
		HP	T			EXT
		FLAT	P				REAR
			U
			T		FRONT LP		INPUT
				INT	SUB		KAPPA 52a
				SUBWOOFER
				EXT	INPUT
		Rear L/R Inputs
	(from Source Unit)								To Rear L/R
									Speakers

5

L

Midbass

R

Midbass

To L/R

Midrange

Speakers

To L/R

Midbass

Speakers

Kappa 255a

P R E C A U T I O N S A N D N O T E S

•The Kappa 255a has five levels of circuit protection that monitor the amplifier and will shut it down if the electrical system voltage drops below 10 Vdc or exceeds 15.5 Vdc, temperatures are above 194° F (90° C), short circuits occur, or current draw exceeds product specifications. For best performance, check the intended mounting site to make sure the operating environment does not create conditions that will trigger circuit protection.

•Prior to installation, turn off all audio systems and other electrical devices. Also disconnect the (–) negative lead from the vehicle’s battery.

•At the installation site, locate and make a note of all fuel lines, hydraulic brake lines, and electrical wiring. Use extreme caution when cutting or drilling in and around these areas.

•Use the amplifier as a mounting template to mark locations for the mounting holes.

•Check clearances on both sides of a planned mounting surface before drilling any holes or installing any screws. Remember that mounting screws can extend up to an inch behind the surface.

•Always wear protective eyewear when using tools.

•The Kappa 255a uses gold-plated, industrial-grade Weco® plug-in connectors for power and speaker wiring. Because of precision tolerances, do not insert the connectors into the amplifier without pre-wiring them first. Once the wires are fastened in each shell, they provide additional gripping area for easy connector removal.

•When routing cables, keep input signal cables away from power cables and output speaker wires, as shown in Figure 5 (below).

•When making connections, make sure that each connection is clean and properly secured. Observe the

polarity markings on the front and rear panels. Refer to the application drawings (Figures 1 through 3 on pages 4 and 5) to set up the amplifier for operation of various configurations.

•If the amplifier’s fuses need replacement, use only

the same rating and type as replacements. Do not substitute another kind.

SPEAKER Cables

		RF	RR
			AUDIO Cables
	Chassis		Source
			Unit
	Ground		SUB
		Ignition
Battery		LF	LR	Kappa 255a
–	Fuses			Amplifier
	+
Chassis
Ground				Chassis
				Ground

POWER and

REMOTE Cables

Figure 5. To minimize possible noise pickup, use this suggested cable routing scheme to plan your amplifier installation.

6

Kappa 255a

I N S T A L L A T I O N

The Kappa 255a is easy to install. For optimum performance, we recommend using high-quality, twistedpair shielded RCA audio cables and 14-gauge or larger speaker wire. Also, you’ll need a minimum of 10-gauge stranded copper wire (e.g., red and black jackets) for the power connections. Use 18-gauge (e.g., blue jacket) wire for remote turn-on.

Depending on your total system plan, allow for adequate time and the possibility of overnight storage of your vehicle, since it may take more than one day to complete the installation.

M O U N T I N G T H E A M P L I F I E R . . .

The Kappa 255a can be mounted in virtually any location inside the vehicle. However, make sure to keep the amplifier away from heater vents or ducts.

1.At the chosen site, use the amplifier as a mounting template and mark locations of the four mounting holes.

2.Drill a small pilot hole at each marked location.

3.Mount the amplifier and securely tighten the mounting screws.

P A R T S L I S T . . .

Examine and verify that the package includes the following items:

•(1) Kappa 255a Power Amplifier

•(2) Spare ATC fast-blow fuses (40 A)

•(1) Control cover with (2) machine screws

•(1) Weco 5-pin audio connector

•(2) Weco 4-pin audio connectors

•(1) Weco 2-pin power connector

•(4) #8 mounting screws

W I R I N G T H E A M P L I F I E R . . .

Refer to Figure 6 (below) for details of the Kappa 255a’s front and rear panel connections.

1.For power, remote, and speaker wires, strip 1 ⁄4" off one end of each jacket to reveal bare wire for insertion into the Weco connectors.

2.Using the Weco 2-pin power connector, connect a black wire from the nearest bare-metal chassis component to the (–) terminal. Then, connect a red wire from the vehicle’s +12-volt battery terminal to the (+) terminal.

3.Make sure the wires are firmly seated in the Weco 2-pin connector and that each screw is completely tightened. Insert the wired connector into the POWER socket (on the amplifier’s rear panel). Press it in until it stops.

KAPPA 255a WIRING CONNECTIONS

(front panel)

RL

KAPPA 255a WIRING CONNECTIONS

(rear panel)

Figure 6. Wiring connections for the Kappa 255a amplifier.

7

Kappa 255a

I N S T A L L A T I O N ( c o n t i n u e d )

4.Using the Weco 5-pin connector, connect a blue wire from the source unit’s remote connection to the REM terminal. Depending on polarity requirements (see Figures 1

through 3 on pages 4 and 5), connect speaker wires from the subwoofer(s) to the L and R (+ and –) terminals, as required by your system plan.

5.Make sure the wires are firmly seated in the Weco 5-pin connector and that each screw is completely tightened. Insert the wired Weco 5-pin connector into the SUBWOOFER socket (on the amplifier’s rear panel). Press it in until it stops.

6.Using Weco 4-pin connectors, connect speaker wires from

the front and rear speakers to the amplifier. Depending on your system plan (see Figures 1 through 3 on pages 4 and 5), match the polarities on the L and R (+ and –) terminals.

NOTE: In 3-way applications, the rear amplifier provides bandpass channels to drive midrange or midbass speakers.

7. Make sure the wires are firmly seated in each Weco 4- pin connector and that each screw is completely tightened. Insert the wired Weco 4-pin connectors into the FRONT and REAR sockets (on the amplifier’s front panel). Press each one in until it stops.

8.Connect RCA cables from a source unit to the L /R, FRONT/REAR INPUT jacks. If the source unit has subwoofer outputs, also connect a pair of RCA cables from those jacks to the SUB INPUT jacks and set the SUB INPUT switch to EXT (see Figure 7).

S E T T I N G T H E C R O S S O V E R S . . .

1.To use the Kappa 255a in a front/rear system, set the CROSSOVER controls to frequencies recommended by the speaker manufacturer (see Figure 7). If the value is unknown, set the control midway.

2.For a 3-way system, set the OUTPUT and REAR INPUT

switches to create the appropriate bandpass filters (see Figures 2 and 3 on pages 4 and 5).

x15	FRONT
	C	9V		G
				A
x1	R
				I
	O
	S	.25V		N
	S
32Hz	O			32Hz
	V		M
	E	BR
320Hz	R		O	320Hz
	O	ST	D
LP			E	LP
	U
HP	T			HP
FLAT	P			FLAT
	U
	T
	50W X 4
	+
200W CLASS D
DIGITAL SUBWOOFER
AMPLIFIER

	REAR				SUBWOOFER
C		9V		G	9V	G
				A		A
R
				I		I
O		.25V			.25V
S				N		N
S					20Hz
O
V		M		FREQ
E	BR		D
R		O			80Hz
	ST	D	B
O					MIN
		E
U			O		Q
T
P
U					MAX
T			INT			SUB
			EXT			INPUT
			X		32Hz
			O			60
			V
			E			Hz
			R	320Hz
			EXT			REAR
		FRONT LP				INPUT

S E T T I N G I N P U T S E N S I T I V I T Y . . .

Initially, turn the front and rear input sensitivity GAIN controls to their minimum (counter-clockwise) positions (refer to Figure 7).

1.Reconnect the (–) negative lead to your vehicle’s battery. Apply power to the audio system and play a favorite music track from CD or tape.

NOTE: After the source unit is on, green LEDs (on the top panel) will illuminate, indicating the amplifier is on. If not, check the wiring, especially the remote connection from the source unit. Also refer to “Troubleshooting” on the next page.

2.On the source unit, increase the volume control to maximum position. Slowly increase the Front and Rear GAIN controls (clockwise) towards three o’ clock and, at the same time, listen to the quality of the reproduced sound. At some point, you’ll hear distortion on the music peaks. Stop the adjustment and turn it back slightly.

S E T T I N G D B O . . .

Dynamic Bass Optimizer (DBO) is a new approach to enhancing low-frequency reproduction in a vehicle. Conventional bass boost controls add bass at a fixed frequency and cause the amplifier to consume considerable power. DBO conserves valuable power at the lowest frequencies and allows you to adjust the level and “character” of the bass sound, instead of just the amount of boom.

Since a subwoofer in a tuned box is given to overexcursion below the tuned frequency, set the FREQ control below the box’s resonant (tuned) frequency (see Figure 8 on page 2). Power typically wasted in this region will now be conserved and instead be available for frequencies the enclosure will reproduce. Use the Q control to boost the

bass at the set frequency by as much as 12 dB (at MAX position – see Figure 8 on Page 2).

For sealed enclosures, use DBO to enhance the output so it sounds more like a tuned box. This is a result of 12 dB of rolloff being added to the enclosure’s rolloff and a flattening of frequency response (at the curve’s knee) when Q is boosted.

For infinite baffles, set the FREQ control to the speaker’s Fs value (to keep the subwoofer from trying to create bass below the resonant frequency) and adjust the Q control according to personal taste.

I N S T A L L I N G T H E C O N T R O L C O V E R . . .

After wiring and testing the Kappa 255a amplifier, install the control cover using the enclosed machine screws to deter tampering and help seal out dust.

NOTE: Do not over-tighten the machine screws. Doing so may crack the cover.

Figure 7. Kappa 255a controls for crossover, input, output, and DBO (Dynamic Bass Optimizer).

8

Kappa 255a

T R O U B L E S H O O T I N G

Use the following guide to identify symptoms and solve problems. Make sure the vehicle’s electrical system is working properly and power is reaching the Kappa 255a (i.e., green LEDs on the top panel are on).

SYMPTOM	LIKELY CAUSE	SOLUTION
No audio	Low/No Remote	Check connections;
	Turn-On Voltage	test turn-on voltage
	Speakers are not	Check wiring; use
	connected or are	VOM/DVM to
	blown	measure speaker
		coil impedance
Distorted audio	Input sensitivity	See Setting Input
	is not set properly	Sensitivity on
		previous page
Audio lacks	Speakers are wired	Check polarity of
“punch”	with wrong polarity	connections; refer to
		Applications

SYMPTOM	LIKELY CAUSE	SOLUTION
Audio cycles	A protection circuit	Verify the following–
off and on;	is turning the	electrical system is
Amber protec-	amplifier off and on	between 10 ~ 15.5 Vdc;
tion LEDs (on		temperature is not
top panel) are on		over 194°F (90°C);
		no short circuits;
		speaker loads are not
		less than 1 ohm
		(2 ohms in mono)
Audio cycles	GAIN is set too high	Set Input Sensitivity
off and on;		correctly (see previous
Amber protection		page)
LEDs (on top
panel) are on
Fuse blows	Incorrect wiring or	Check connections;
	short circuit	refer to Applications

9

Kappa 255a

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 Surface Mount Devices.

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 to 2.2k (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 to 2.2k (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	Damaged Q10,11,12 or 13	Change R3 & R15
	below -01701		to 2.2k
KAPPA 255a	“HC” in the prefix	Modified by factory	NONE REQUIRED
	-01701and above

10

Kappa 255a

	Service Bulletin
Service Bulletin INF2001-02 - September 2001		Warranty labor rate: MAJOR repair
To: All Infinity Service Centers
Model: Kappa 255a
Subject: No Sound from Subwoofer Output

In the event you receive a Kappa 255a with the complaint: “No sound from the subwoofer output”, replace transistor Q18 SMD (Surface Mount Device) with a TO-220 package, TIP31C transistor. For details, see instructions as described below. All KAPPA 255A amplifiers with serial numbers starting with letters “CL” should be modified. The serial number is printed on a white label, located on the bottom of the Kappa 255A enclosure.

Note: Many components in this product, including the one due for replacement, are Surface Mount Devices.

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 heatsink.

4)Locate, identify, and remove Q18 SMD transistor on the bottom of the main PCB. See illustrations on page 2.

5)Prepare the nearby area on the PCB by applying a white .5" x .75" BONDPLY insulator, (Infinity part# TO-220 BONDPLY-100) in the area where a new TIP31C transistor will be mounted.

6)Apply a transistor TIP31C (Infinity part# TR1183) on top of the insulator; press firmly to set. Transistor should be flat on the PCB.

7)Extend the three leads of the transistor by soldering a length of 22 gauge buss wire to each lead, the length determined by the connection points. Solder each wire piece to each lead (longer is better as it can always be cut) and then trim to the correct length. You will NOT be re-connecting the three leads to the tiny solder pads for the original SMD device; study the illustrations to locate the three final connection points.

8)Cut three pieces of 1/16” vinyl or shrink tubing to insulate the three exposed leads, leaving enough wire exposed at the end to make the final soldered connections.

9)Solder the three leads in the areas shown in the illustration. Transistor Q18 and new connecting wires MUST NOT be higher than the square plastic standoff next to it.

10)Add a dab of RTV (silicon seal or similar non-conductive compound) to the area of the three leads.

11)Test the unit, still out of the heatsink, by applying power, with signal and subwoofer connections WITH NO LOUDSPEAKER LOAD other than a DMM or an oscilloscope on the output terminals.

12)Reinsert main PCB into chassis; confirm that all (20) insulators on the output devices are still in place, attached with heat sink compound on each one.

13)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.

14)Attach all power, speaker and signal cables to amplifier and test with loudspeaker load.

	MODEL	SERIAL NUMBER	STATUS	ACTION
	KAPPA 255a	“CL” in the serial # prefix	Q18 Overheating	Replace Q18 with
		All units affected		TIP31C transistor

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Kappa 255a

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Kappa 255a

Kappa 255a Exploded View

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