Hi,

The signals are buffered (2 dual op-amps) actually, they have a gain of 2, that feed the sled connector outputs. The Line out RCA connectors are ahead of the buffer. As Tony says, this really limits the area that could be a problem. For the problem to affect the Front and Rear Left only, the areas to check are:

1) Both dual buffers could be bad (one dual buffer has Left and Right Rear outputs, the other dual buffer has Left and Right Front outputs). This is unlikely unless a large voltage was applied to the left sled outputs damaging the buffers. It would more likely be #2 or #3 below.

2) Both Left Front and Left Rear output 100 Ohm series current limiting resistors could be open (cracked or blown open - only mostly dead because it is intermittent). Look for blown or cracked 100 Ohm resistors on the board near the connector area.

3) The Front and Rear Sled Connector Ground pins (16 & 19) could be open or not connected. You should measure 1.2k from pins 16 & 19 to the Player Chassis. You should also be able to see 2.4k from pin 16 to pin 19.

4) You do have the correct pins connected on the Sled Connector, right? I had to ask for completeness...

Often amplifers and head units have blown grounds internal to the units because of poor ground selection during installation. The "ground" from the head unit to the amplifier can be completed through the RCA connectors and cable if a poor ground on either the head unit or amplifier is not robust. This means a very good ground is neccessary at the Power Amplifier(s) - that's where the majority of the current is - so that the ground currents prefer that path (lower DC Resistance in this case), instead of through the head unit ground wire to chassis/battery connection.

The amplifier ground connection can become compromised over time (oxidized if not properly prepared and sealed after the connection is made). Make sure that you actually have a good solid connection back to the common frame the battery is connected to - some chassis are made up of multiple members. This is going to be more of a problem with future cars.

All of a sudden, you lose "stereo separation" or it doesn't work any more. When you open the head unit or power amplifier, the ground trace/plane is open to the RCA connectors. Fix the ground connection on the Amplifier(s), fix the trace(s) and see if it works again.

Ross