Do you have Hi-Line Nav? Then you'll want to read this! BM24 upgrade and repair info.

[DMGRS]

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:
http://i282.photobucket.com/albums/kk245/mattyprice4004/2011-04-0903-25-41-Backups10011_zpsfbe00f3a.jpg~original (http://s282.photobucket.com/user/mattyprice4004/media/2011-04-0903-25-41-Backups10011_zpsfbe00f3a.jpg.html)

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.
http://i282.photobucket.com/albums/kk245/mattyprice4004/2011-04-0902-51-16-Backups10006_zpse7712646.jpg~original (http://s282.photobucket.com/user/mattyprice4004/media/2011-04-0902-51-16-Backups10006_zpse7712646.jpg.html)

Next, remove the PCB from the metal casing:
http://i282.photobucket.com/albums/kk245/mattyprice4004/2011-04-0902-52-07-Backups10008_zps5ceeb41e.jpg~original (http://s282.photobucket.com/user/mattyprice4004/media/2011-04-0902-52-07-Backups10008_zps5ceeb41e.jpg.html)

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.
http://i282.photobucket.com/albums/kk245/mattyprice4004/2011-04-0903-00-30-Backups10009_zpsce151426.jpg~original (http://s282.photobucket.com/user/mattyprice4004/media/2011-04-0903-00-30-Backups10009_zpsce151426.jpg.html)

Re-assemble the unit and you're done! It should all work perfectly. :)

[MGRick]

Would the bm24 make a difference in audio if you have the hk amp fitted ?

[DMGRS]

Would the bm24 make a difference in audio if you have the hk amp fitted ?

The HK uses speaker-level inputs, so I can't imagine it making that much of a difference. I'd find a member who has one at a meet to try a swap - I have noticed more bass presence with the BM24 but that may not apply when using the HK amp.

[scoubix]

The HK uses speaker-level inputs, so I can't imagine it making that much of a difference. I'd find a member who has one at a meet to try a swap - I have noticed more bass presence with the BM24 but that may not apply when using the HK amp.

Actually it might very well make a difference since, as you said so yourself, the HK amp uses speaker outputs from the radio module, not line-level outputs which do not exist. Therefore, the quality of the sound at the output of the radio module, be it the OEM one or a BM24, makes a difference in the final sound quality once amplified by the HK. I don't own a HK setup myself but considering the vast difference in sound quality from the OEM module to the BM24 one, this should result in better sound quality when paired with the HK.

[DMGRS]

Actually it might very well make a difference since, as you said so yourself, the HK amp uses speaker outputs from the radio module, not line-level outputs which do not exist. Therefore, the quality of the sound at the output of the radio module, be it the OEM one or a BM24, makes a difference in the final sound quality once amplified by the HK. I don't own a HK setup myself but considering the vast difference in sound quality from the OEM module to the BM24 one, this should result in better sound quality when paired with the HK.

I guess it depends on how the HK amp 'loads' the input - if it 'pretends' to be a 4 ohm speaker then the sound quality will indeed benefit. If it's 'unweighted' the Philips unit may well be adequate, as there will be very little load presented.

Worth a try, as the BM24 is certainly a very good improvement.

[Bolin]

Thanks for the guide. One question - I can solder wires together OK, so will I be able to solder the joints you mention without having done hardly any soldering on a PCB before (can't remember when I last did, maybe done it once or twice before) or do I need to be fairly experienced at soldering before attempting this? i.e. is it easy to mess up?

P.S. I went from Symphony non-HK to Highline BM24 with HK and it's miles better - even I could tell that despite knowing nothing about car audio!

[Ross R75]

Great post Matty, thanks. I just picked a BM24 up on EBay for £65. A fairly decent price I think :)

[DMGRS]

Thanks for the guide. One question - I can solder wires together OK, so will I be able to solder the joints you mention without having done hardly any soldering on a PCB before (can't remember when I last did, maybe done it once or twice before) or do I need to be fairly experienced at soldering before attempting this? i.e. is it easy to mess up?

P.S. I went from Symphony non-HK to Highline BM24 with HK and it's miles better - even I could tell that despite knowing nothing about car audio!
It's really easy, just make sure you have a high-powered iron (30w+) as the solder is a right pain to melt. :D

Great post Matty, thanks. I just picked a BM24 up on EBay for £65. A fairly decent price I think :)
Wow, you beat mine at £70! Well done, a great price.

[bazza004]

I have BM24 just installed,and its live,screen on but wont tune-in any channels,could the cracking joints be responsible ?

[Heddy]

Great post Matty, thanks. I just picked a BM24 up on EBay for £65. A fairly decent price I think :)
And it's still working just fine, especially with the upgraded speakers.

[madeupname]

Hi Mat. I seee this is an old thread, but I've had to replace the original tuner on Kim due to rust, with a BM54.
I presume the 54 is an updated version of the 24. Is this correct?
Also, it has a 10amp fuse on it where the original had a 5amp fuse. Will using this create any problems?
Thank you,
Adrian.

[Canonite]

If you bought a round pin BM54 Back then it’s not that different to the BM24.
If you bought a flat pin version, and have the adaptor, I’d love to try it in my Typhoon before buying one.

[madeupname]

Thanks Al.
I think it has round pins because the original connector fits.
Trim and seats are still out of Kim so the battery is disconnected. Hopefully over the next few days I'll have everything cleaned up and put back in.
Kims radio never worked. I discovered this was because water in the boot had rusted the coax connector. I've put a spare aerial on (had to snip the coax to get the cable through the rubber grommet under the parcel shelf) but as soon as the battery is reconnected I'll see if it works.
I didn't buy it, I got it from a forum member in Hull when I took him a diesel radiator he needed.
On the unit it says - BMW Professional BM54.
Adrian.

[DMGRS]

Hello there, I think Canonite is spot on here - they're not that different and I'd give it a try.
The 10a fuse is purely because the amplifier circuitry in these units is much more beefy than the original Rover item.