Today at Atelier Kaz - ex-Honda R&D, F1, Indy/CART engineer

The owner told me that the passenger side foot well speaker as well as
the centre one were dead for quite a while and on the way to my place,
he started to hear cracking noise from the left side door speaker.

So, started to check the status of the existing AMPs.




The door AMP.

It’s the later spec one with several updates.
On the bench, there was no noise at all and the gain control was
also fine.




Removed the capacitors and while there was tiny leakage,
there was no damages to the track so there is a chance that
the cracking noise was actually caused by the capacitor leakage
inside the audio head unit itself.
Will replace all AMP capacitors with up-rated ones any way because
they will leak eventually.





The foot well bass AMP.

This is the one driving the foot well speaker as well as the centre one.
To my surprise, the AMP inside the speaker box was the original design one.
It was still using the green coloured capacitors.




Bose made at least three revisions for the foot well AMP on our NSX
so I was expecting to see the 2nd generation one but the
date stamped on the foot well speaker was from 1991 that is
way too old considering the year model of this NSX.

May be previous owner replaced it in the past???


Any way, on the bench, it was properly dead.

Not even the switching noise was heard and just few 10mA current flow.





There were lots of capacitor leakages and because they were left for many years,
the acid managed to run down below the coil area.




I had to remove one of them for inspection and cleaning.



Removed all of the acid as much as possible and then started the repair.



All capacitors replaced, bench tested it and checked the gain control.

It operated fine and now the sound is back.


Will apply the thermal compound below each FETs, hot melt glue,
conformal coating followed by at least 2Hrs of testing before
installing it back to the car.



Wanted to carry on working on the door AMP but found out that
the package from Japan arrived at my local depot so instead of
waiting for the delivery on Monday, decided to collect it to save
some time.

Hope to finish the AMP service in the near future.


Time to work on the engine again.


Kaz