Radio Repaired

Hi Folks,

Since I have used this forum quite a bit since purchasing my Disco 2 I thought it a good idea to add updates on any successful repairs I have made which may help somebody else in the future.

I bought the car with a broken radio head unit. It came with a R990 Highline stereo with cd changer and amp. The car had two leaks and signs of a spill for the stupidly placed cup holders. I guessed it was a blown head unit due to some form of liquid ingress. I tried to buy a replacement unit or even send it for repair but it would have been just as cheap to buy a totally new head unit.

I checked all the usual suspect fuses etc to no avail, but to cut a long story shorter, when I had finally given up and resigned myself to buying a new unit, I turned the car on one morning and heard a strange noise coming from the A frame speakers. I pressed the button and the radio came on looking for the code. Once inserted it worked!!!!!

Two days later it died but at least I knew the dam thing wasn't dead. I finally set to work on the complete circuit and I found and repaired the problem, so heres what I did;

First I printed out the relevant sections from the workshop manual. I fashioned two plastic inserts from the cover of a binder to remove the radio. Using a multimeter I started at the battery and did continuity test along each part of the circuit from the battery right through to the head unit. All links and fuses were ok so it could only be the head unit. I removed the switch and then the four screws to take off the face plate and the top of the unit. I suspected the switch or power input. I rigged up a dc power supply using a 12v dc supply. I made two spade connectors to connect to the purple power input and the black earth. I then started to measure the voltages at the switch but to be honest could not make sense of them.

I decided to take a closer look at the circuit so I took off the front printed circuit board by un-soldering it. I saw no signs of burns or problems here. I removed four screws to release the cassette player nothing look out of place on this circuit. I then removed the remaining screws, solder clips and removed the mother board. When I flipped it over the was some noticeable efflorescence around a integrated circuit (small black chip) and this white crusty stuff extended across to the two thermistors another two chip like things with three pins attached to two black cooling fins. I cleaned off the surface using an old dry toothbrush. Upon close examination I could see that two of the pins on the chip were attached by solder. This seemed out of place for this circuit so using a soldering iron I melted this link and removed the excess with a solder sucker. A smaller chip on the board as well as one of the thermistors looked like the solder was in poor condition so I brushed these with new solder just to make sure.

I re assembled the unit and connected it in the car and it worked perfectly. I reinstalled it and it is still working now two weeks later.

All in all it took about four hours to trace the circuits and then test the head unit. I choose to test the circuits in the car first as they would have been easier to fix. Once I knew it was the head unit then I started in there. Working on these circuits is usually quite tricky and involves a lot of luck. I don't know precisely what the cause was. The solder between the pins or loose solder in the circuits. My guess is that is was the solder bridge between the pins that caused other parts of the circuit to overheat hence the white efflorescence on the chips.

I have worked with electronics a little in the past so I was no stranger to the components but to be honest a little investigation and common sense will get you a long way. If the unit appears to be dead then you have nothing to loose by tinkering with it.

Regards

With my limited ability in the electronics side of things that counts as pretty brave, and to succeed with a DIY job is always satisfying, it helps to know as an amateur that there is such a thing as a 'solder sucker', one for Santa's list methinks!!

And it still working.

Does anybody know how to add an aux input jack onto this unit? It is a standard factory Alpine head unit with no RCA inlets at the rear. I know the radio repair guys in the UK advertise this addition as a service.

I believe that I can do this myself however, I am uncertain of the wiring. Any advice, schematics or wiring diagrams would be welcome.

I am hoping that I can solder the wiring internally and add the auxiliary jack to the fascia of the head unit.

Regards

This is a lot more impressive than my only repair so far, spray painting the centre caps on the alloys :focus:

Hi Folks,

Still trying to get information on the wiring when adding an auxillary jack socket to the head unit so I can connect my phone to it and play my music directly.

All I need is a wiring diagram as to where the wires should be connected internally. Has anybody had theirs fitted with this modification and if so could you help.

Any advice is much appreciated.

Regards

I just managed to fix my radio too although I suspect it hadn't had as much of a soaking as irish4x4's. All mine took, was the dismantling and then a soft brass wire brush on the circuit board at the L hand side - just where the big power transistors (?) are. There was a little corrosion and some build up of gunk between some tiny circuit board tracks but they cleaned up nicely and the radio powered up first go!
As for wiring in an Aux socket, it doesn't look too bad a job to do in the future. A useful wiring diagram is at Connector. I'm just not sure how channel R +ve and -ve and channel L +vs and -ve and an Earth translate to the three connectors on a 3.5mm stereo jack. Presumably L and R -ve's connect to Earth.... I'll give it a bash!

cromar said:

I just managed to fix my radio too although I suspect it hadn't had as much of a soaking as irish4x4's. All mine took, was the dismantling and then a soft brass wire brush on the circuit board at the L hand side - just where the big power transistors (?) are. There was a little corrosion and some build up of gunk between some tiny circuit board tracks but they cleaned up nicely and the radio powered up first go!
As for wiring in an Aux socket, it doesn't look too bad a job to do in the future. A useful wiring diagram is at Connector. I'm just not sure how channel R +ve and -ve and channel L +vs and -ve and an Earth translate to the three connectors on a 3.5mm stereo jack. Presumably L and R -ve's connect to Earth.... I'll give it a bash!

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I'm wishing I took my knackered one apart now,I found a replacement on Ebay and luckily it works ok(my old one had water ingress from front sunroof leakage)