Saturday, November 21, 2015

JBL BP1200.I MODIFICATION POWER SUPPLY AND POWER AMP CIRCUIT

JBL BP1200.1

MODIFICATION POWER SUPPLY AND POWER AMP CIRCUIT 

Muting during intense bass passages (MODIFICATION)
Under certain large signal conditions during intense bass passages, the unit will go into protection. These amplifiers are behaving as designed. As the unit is driven into hard clipping, the protection circuit found in BP Series amps was engineered to protect your loudspeakers from being destroyed by a severely clipped output signal. This can be remedied easily by turning the volume down somewhat on your music source.
In the event you receive a BP series amplifier with the complaint: “Under a large signal input, with music that is composed of high-level bass, the amplifier mutes for 2-3 seconds, and then returns to normal operation”, the following modification will effectively increase the amount of clipping that is allowed to occur before the protection circuit engages by increasing the threshold at which the amplifier mutes - for the benefit of customers who use the amps in SPL competition, or for customers who insist on driving the amplifiers into this potentially hazardous zone.
1) Turn the amplifier upside-down and remove the Phillips screws holding the bottom cover on.
2) Locate and change R510 from 47K to 4.7K ohms 1/5W (JBL part# RE212047200).
3) Locate and change R511 from 22K to 2.2K ohms 1/4W (JBL part# QAF0450-222).
4) If it is not already present, add new part - 4.7uf 50v electrolytic capacitor (JLB part# EC070114760) in parallel with R511. Polarity: The negative side of the capacitor must be connected to the junction of R510/R511, which can be discovered with an ohmmeter.
NOTE: Using the correct soldering techniques, you should be able to make these changes from the top of the PCB without its removal.
5) Replace bottom cover; test amplifier

Controls and Connections

1. It allows left and right input channels to be connected to the amplifier using RCA plugs.
2. Speaker Output Connector - Connect speaker wiring to these connectors..
3. Fuse - 40Ax3 Amp ATC type Fuses.
4. Power Connection for 12V+, GND and REM connections for power wires.
Mounting the Amplifier
The amplifiers 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 the 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.
5. Input-Level Control - Adjusts input sensitivity for pre-amp level and speaker level inputs.
6. The electronic crossover is a 12dB/oct. Low pass filter which can be Set at any frequency between 32Hz and 320Hz.
7. The bass boost control will provide up to 6dB of boost at 50Hz.
8.It allows left and righ input channels such as high level speaker output signals to be the amplifier.
INVERTER POWER SUPPLY CIRCUIT 
USING TL494 - IR3205
PRE AMP AND POWER AMP CIRCUIT 
USING IRF9640 -IRF640
CLICK ON THE IMAGE TO ZOOM IN