The CD players fitted to older cars are prone to failure, I stripped and cleaned my single CD which helped but never cured the real problem of skipping or failing to recognise a CD. You can purchase a repair manual (£15) for the single CD/Tuner from Startrade in Australia, I don't know anyone who has tried this fix though.

The rest of the Hi-Fi system is of very poor quality in comparison the car, cheap paper coned speakers are fitted in the front door and rear shelf & low power amplifiers used, some models also had an optional 8" sub-woofer in the rear shelf, this was made by Nakamichi but certainly made to a price.

Replacement Head Unit:

This is a nightmare, as you can see from above the standard units are huge and not exactly square making replacement very difficult. The most common replacement is a double DIN unit as it almost fills the hole left when the original head unit is removed, unfortunately most of the double DIN units look more like a Space Invaders game than a car Hi-Fi.

Becker Mexico Pro CD/Tuner

Matching the looks of the existing air-con was my goal here and I managed to find a "black" unit from Becker the only other choice was a s/hand unit like Blaupunkt, but matching the illumination is almost impossible.

The Mexico Pro is very high specification with Single CD, RDS Tuner, 4x20w RMS, F/R & Sub Pre-Outs and the option of adding a 10 disc changer.

I am hoping to change the air-con display to Orange one day, can anyone help with this?

Front Speakers:

As mentioned the speakers fitted are low quality and present a poor stereo image, just straight replacements of the 4" in the front door & 6.5" rear shelf speakers would be a useful upgrade but the low power output is still an issue. Wanting to create a reasonable Hi-Fi system I decided to replace the front speaker system (4" mids in the door & tweeters up above) with the JBL GT Series, 4" midrange (70w RMS)  fitted in the original mountings with a little work making a spacer ring from MDF (fibre-board) as the original speakers are nearer to 4.25" and left an air gap around the 4" JBL midrange drivers. The factory mounting is actually a small bass reflex chamber, removing this chamber would allow a bigger driver to be installed directly into the door, this would entail making a new mounting plate which needs to sealed against the door frame.

Rear Speakers:

Mounted under the rear shelf cover are the 6.5" standard speakers running full range. These where removed to make way for new Infinity Kappa's 2way drivers (150w RMS) and utilised the existing factory grills set into the rear cover.

Sub Woofer:

My TT just had the hole (no bass driver) , mounting depth is an issue here as the fuel tank is directly underneath making the choice of sub a bit limited and I also wanted to keep the driver under the rear cover. After taking some measurements I decided the Rockford Fosgate 8" Punch (350w RMS) would provide the desired amount of bass. A custom mounting ring was made up and sealed to the steel deck, the sub was mounted into this and a dummy 6"x9" grill fixed on the rear cover and painted to match the original rear speaker grills.

The Rockford sub is running "Free-Air" this is not very efficient but creating a sealed enclosure in this location would be a real nasty job. Limiting the sub power to 150w RMS should prevent the driver from hitting the stops and prevent it from destroying itself, the result is passable, little real low bass but plenty from about 50htz upwards.

Amplifiers

Ignoring all the original amps and speaker cables I installed a Kenwood 4x75w RMS amp for the front/rear systems and another Kenwood 2x75w RMS to drive the 8" Rockford Subwoofer. The latest range of Kenwood amps have built in active crossovers allowing me to use the High-Pass (100htz) for the front & rears to limit the amount of bass the smaller drivers would try to put out, the other amp was bridged into mono and used the amp's Low-Pass filter set around 100htz. 

Locating the amps is another problem, for such a big car there is little space that is not taken up with electronics, the only usable space I found was directly above the tank (I had the fuel tank cover removed to measure the sub mounting depth), this allowed the amps to fit (very tight fit) in-between the sub & rear speakers under the metal rear shelf.

Front Crossovers:

The JBL split mid/tweeter combo is already high-passed from the amplifier (100htz) but these little 4" drivers will give up at higher levels trying to create the lower mid bass, a custom crossover was installed to make them high-pass at about 180htz.