The 1990 300zx 2+2 is one of the few cars in the world ever to have a center channel (they changed the DIN to a crap-holder in 1991). From an acoustics standpoint… it’s probably a bad idea.  But, it’s novel and I’ve decided to keep it.  To restore the amplifier for the central channel , you’ll have to remove the unit. This can be done by following directions for removing the head unit. There are plenty of guides out there for doing this, so I won’t re-write those guides.

Once the head unit is exposed, you will see the classic Bose speaker cloth covering the DIN below the cassette player. Remove the 2 screws on each side of the center speaker channel, and unplug the connector from the back. This black box contains a small speaker and an amplifier.

Using a 5mm socket, remove the screws on the top of the unit. At this point you can crack open the unit to see the small speaker and amplifier. The amplifier is unlike other amplifiers found in Bose-equipped vehicles. It only has one IC chip compared to the two found on most of  their automotive amplifiers. There are a few quirks that I can’t really place reason behind on the unit. The enclosure is unsealed, nor ported; it has vents for the heatsinks. I’m not sure how great a downward-firing speaker in an unsealed enclosure can be tuned.  I’m not going to question it, I’m just going to refurbish it.

Upon inspecting the amp, 8 electrolytic capacitors can be seen. There are 4 shiny green small cylindrical capacitors, and 4 larger blue cylindrical capacitors. I used Parts Express to order my parts. Its easier to use than Digikey. Here is what is needed to replace the electrolytic capacitors:

• 4.7uF  x1
• 47uF  x3
• 100uF x2
• 220uF x1
• 1000uF x1

For all of these, I’ve opted for 50v and 105*c tolerances. You can look on the sides of the caps to find what Bose installed, but keep in mind what I said earlier about the 16v caps they used. Using 50v for all of them made the ordering process easier. It did cost about 10 cents more, though.

Remove the goop by heating it with a heat gun or space heater. I used a combo of a pocket knife, needle nose pliers, and snips. Heat the solder and suck it up with a solder sucker. Be sure to note the polarity of the caps as they are removed.