Classic Mercedes Benz diagnostics, consultations, inspections
Do you have crackling or popping sounds coming from the speakers? Strange UFO type noises? It’s not an alien that lives in your speakers. It’s capacitors that dried up in your Bose amplifier. Capacitors could be replaced to make your stereo sound brand new again.
When I bought my Mercedes 1992 500sel Bose amplifier was missing. Previous owner had an aftermarket radio installed and installers butchered half of wiring in the trunk to get an aftermarket radio to work. And on top of that, they connected speakers wrong. 1992-1993 Bose amplifier sends full pass sound to front speakers, high pass to rear door speakers, bass to four rear deck speakers, and high pass to the center channel behind the rearview mirror. And there is a fader control that connects directly to the amplifier. Stereo shop cut all wires to amplifier, spliced wires from the aftermarket radio into stock wires. Now, fader didn’t work, the center channel speaker didn’t work, full pass signal was sent to all speakers, antenna didn’t work. The radio sounded horrible even though it was $500 Alpine unit.
Long story short, I bought a used Bose amp on eBay for around $120. Great deal I thought. Once installed speakers started to make crackling and popping noises. I was very upset and after some research I found out that all capacitors had to be replaced. I opened up the amp, made a list of dried electrolytic capacitors, ordered and re-soldered them. And to integrate aftermarket radio with Bose amplifier correctly, I soldered RCA pigtails directly into the amplifier. On top I installed subwoofers with separate amplifier. My stereo sounded awesome :) Everyone who drove in my car always asked what system I had. When they were told that the system is stock with aftermarket radio and subs they were amazed. I have very good ears and I need my sound quality to be perfect. S-class sound system is amazing if done right. Newer Bose amps 1994-1999 are slightly different in design and head unit controls fader and radio tuner. In pre-94 models fader was controlled separately on the center console and there is a separate tuner unit in the trunk for AM/FM.
To sum, if your Bose amplifier doesn’t work right, you have four options-rebuild it, buy new one at the dealer, buy used or rebuilt one, replace your whole audio system with new amps and radio. Rather than spending a small fortune for new amp at the dealer you would probably go with used one. But used amp might not work for long if at all. 25 years old capacitors are all dried up. Properly rebuilt amps are not cheap and not easy to find. Replacing the whole audio system the right way in W140 will a cost small fortune depending what amps, speakers, and radio you buy. I think the best option is to rebuild original factory Bose amplifier. An aftermarket headunit can also be installed. With proper setup sound system will sound awesome.
94-99 Bose amps are re-designed and don’t fail as often. But they sustain water damage due to leaking antenna seal. Sometimes damages are too severe and amplifier cannot be repaired. 92-93 Bose used amps will have capacitors that are already dry and will not last long, if at all. I know guys who bought few used amplifiers that last few months and fail again. So, as I mentioned before, rebuilding original amplifier is the best option. Contact me for more information.
Below is the video of an amplifier repair progress
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