As a lot of HiLine Nav owners know, the standard system is very useful however lacks audio output power. The reason being the Philips tuner/amp module uses a very small TDA7375 amplifier IC - the maximum output of this amplifier is 4x 7w @ 10% THD (RMS will be significantly lower).
Here's the standard amp IC:
The easiest upgrade to our systems is to fit the rather excellent Becker BM24 unit. This uses twin amplifier ICs to deliver 4x 47w @ 10% THD - a much higher output. It's not about pure power, however - the BM24 provides much more bass response thanks to it's higher power capacity. You really can tell the difference!
Finally, a great feature (and a good reason to upgrade) is also the twin-tuners built into the BM24 - you get a continuously updating list of stations listed below the one you're currently listening to. Very handy as you can flick through the list with the control knob on the head unit, and press to select a station.
Upgrading to a BM24 is very simple - you'll need to go into the spare wheel well, locate the Philips unit (on the right-hand side when looking into the boot) and remove it. The BM24 uses the same connectors as the Philips unit - so it really is plug and play.
The only issue with the BM24 is the solder joints linking the power ICs to the main PCB fracture with vibration and age, meaning your unit may cut in and out (mine took about 5 minutes to power on, and then worked fine).
Fixing this is simple - I've written a guide for doing this below.
First, remove all Torx bolts visible on the outside of the unit, and remove the lid.
Next, remove the PCB from the metal casing:
Finally, reflow the joints circled below. They appear to be high-temperature solder - you'll need to get a fair bit of heat into them! Once you have the joint molten, add a little more solder to keep the joint firm.
Re-assemble the unit and you're done! It should all work perfectly.
