Kappa 255a Automotive Amplifier _ Power Amplifer_Sub-woofer amplifier & Power Supply Schematics [Circuit Diagrams]
Common faults, and repair tips
POWER SUPPLY
POWER AMPLIFIER
SUB-WOOFER AMPLIFIER
FAULTS ARE REPAIR PROCEDURES
Damaged Output Transistors [This is considered as a Major
repair]
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 sub-woofer 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).
[Many components in this product, including two due for
replacement, are Surface Mount Devices.]
Procedure:
* Remove the (24) 9/64” allen screws from both lower sides of the chassis.
* Remove the (2) #10 Torx screws from the bottom chassis underneath the tamper-proof labels.
* Turn amplifier vertically and strike on a hard surface, dislodging the main PCB; slide entire assembly out of the chassis.
* Remove and replace any defective IRFS250 output transistors. (Q10-13 are Infinity part# TR1238)
* Change R3 on the Digital Pre-driver 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.
* 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.
* Remove the (24) 9/64” allen screws from both lower sides of the chassis.
* Remove the (2) #10 Torx screws from the bottom chassis underneath the tamper-proof labels.
* Turn amplifier vertically and strike on a hard surface, dislodging the main PCB; slide entire assembly out of the chassis.
* Remove and replace any defective IRFS250 output transistors. (Q10-13 are Infinity part# TR1238)
* Change R3 on the Digital Pre-driver 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.
* 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.
* Reinsert main PCB into chassis; confirm that all (20)
insulators are still in place, attached with heat sink compound to each output
device.
* 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.}
* Attach all power, speaker and signal cables to amplifier and test.
* 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.}
* Attach all power, speaker and signal cables to amplifier and test.
No Sound from Subwoofer Output
KAPPA 255a > All units exhibiting symptom > Q18 Overheating
> Replace Q18 with TIP31C transistor
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 exhibiting this symptom should be
modified. Note: Many components in this
product, including the one due for replacement, are Surface Mount Devices.
Procedure:
>> Remove the (24) 9/64” Allen screws from both lower sides of the chassis.
>> Remove the (2) #10 Torx screws from the bottom chassis underneath the tamper-proof labels.
>> Turn amplifier vertically and strike on a hard surface, dislodging the main PCB; slide entire assembly out of the heat sink.
>> Locate, identify, and remove Q18 SMD transistor on the bottom of the main PCB.
>> Remove the (24) 9/64” Allen screws from both lower sides of the chassis.
>> Remove the (2) #10 Torx screws from the bottom chassis underneath the tamper-proof labels.
>> Turn amplifier vertically and strike on a hard surface, dislodging the main PCB; slide entire assembly out of the heat sink.
>> Locate, identify, and remove Q18 SMD transistor on the bottom of the main PCB.
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.
>> Apply a transistor TIP31C (Infinity part# TR1183) on top of the insulator; press firmly to set. Transistor should be flat on the PCB.
>> 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.
>> 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.
>> Apply a transistor TIP31C (Infinity part# TR1183) on top of the insulator; press firmly to set. Transistor should be flat on the PCB.
>> 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.
>> 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.
>> 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.
>> Add a dab of RTV (silicon seal or similar non-conductive compound) to the area of the three leads.
>> Test the unit, still out of the heat sink, by applying power, with signal and subwoofer connections WITH NO LOUDSPEAKER LOAD other than a DMM or an oscilloscope on the output terminals.
>> 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.
>> 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.
>> Attach all power, speaker and signal cables to amplifier and test with loudspeaker load.
>> Add a dab of RTV (silicon seal or similar non-conductive compound) to the area of the three leads.
>> Test the unit, still out of the heat sink, by applying power, with signal and subwoofer connections WITH NO LOUDSPEAKER LOAD other than a DMM or an oscilloscope on the output terminals.
>> 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.
>> 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.
>> Attach all power, speaker and signal cables to amplifier and test with loudspeaker load.
CLICK ON THE PICTURES TO MAGNIFY
