Results 1 to 6 of 6

Thread: Radio Head Unit (EU 1991) Repair

  1. #1
    Join Date
    Jan 2018
    Location
    Near Stuttgart, Germany
    Posts
    246
    Blog Entries
    25

    Lightbulb Radio Head Unit (EU 1991) Repair

    A direct message via the the German Motortalk forum reached me. A distressed NSX driver was reporting about trouble with his radio head unit. The volume was unusually low, noise was generated when changing the volume and another repair approach had already failed.
    We talked a bit over the chat and since radios that haven't fully failed yet can often be repaired, decided to ship the unit. When it arrived I had a quick look inside and found an interesting graffiti that even the owner was not aware of, so It's source might stay a mystery.

    Click image for larger version. 

Name:	PXL_20220629_090537479s.jpg 
Views:	589 
Size:	94.7 KB 
ID:	14647

    The first assumption was that leaking capacitors and destroyed PCB traces where the reason for the issue and once repaired would provide a fully working radio. Fortunately or unfortunately, through a previous (and well executed) repair, the radio already gained new capacitors and multiple repaired traces.

    Click image for larger version. 

Name:	PXL_20220629_091744728s.jpg 
Views:	520 
Size:	145.9 KB 
ID:	14648


    This proved, on one hand, that the radio did suffer from leaking capacitors but also that it couldn't be the reason for the current issue – the search continued. All previously added repair bridges were connected correctly and the problem occurred on all audio sources (CD, Cassette, Radio) in exactly the same way. The potential reason therefore had to be near the end of the audio processing chain.

    A check of the power supply for the last amplifiers before the speaker output (IC205 and IC206) yielded no results as the 10 V were absolutely stable (a problem detected in a another repair). Replacing the volume, tone and power supply PCB brought no change either. Out of suspicion, the four larger capacitors used to decouple IC205 and 206, were de-soldered and checked. One of them was a little off so all four where replace. No improvement whatsoever.

    While working on the PCB, an interesting component came into focus - an analogue multiplexing chip named MC14066B, called IC304. He's probably responsible for the audio source selection. If he would be defective, all sources of audio would be affected. Installing a replacement from a broken radio PCB still made the same low and distorted sound appear - no luck again.

    Right next to it is IC303, a four channel OP amplifier named JRC2060. While not 100 % sure what he was supposed to do, measurements where very strange. Correct voltage supply, correct input signal but almost no output .. .. after his replacement, loud and full static noise could finally be heard (the sleeves of the capacitors nearby took a bit of beating due to the hot air soldering but nothing serious).

    Click image for larger version. 

Name:	PXL_20220629_164418037s.jpg 
Views:	523 
Size:	173.9 KB 
ID:	14649


    Click image for larger version. 

Name:	PXL_20220629_173256088s.jpg 
Views:	554 
Size:	148.6 KB 
ID:	14650

    Informing the owner, and he was just as happy as me to hear the the unit was finally fixed. Typical for such endeavours, finding the issue is the tricky part, not so much the repair itself.
    Final test were all fine and the volume button that needed to be removed when testing with a replacement PCB was secured with thread locker to avoid a strange look of the radio front if the knob gets loose.

    Click image for larger version. 

Name:	PXL_20220629_175533547s.jpg 
Views:	478 
Size:	106.7 KB 
ID:	14651

    A significant amount of time went into the analysis but the gained knowledge should come in handy for future repairs. The exchanged ICs (MC14066B and JRC2060) are still available, via the usual channels, btw.
    Last edited by Heineken; 04-07-2022 at 06:46 PM. Reason: Added missing picture
    1997 JDM Custom Order AT VIN 1400005 - Stock
    Heineken's Garage

  2. #2

    Default

    Quote Originally Posted by Heineken View Post

    Click image for larger version. 

Name:	PXL_20220629_090537479s.jpg 
Views:	589 
Size:	94.7 KB 
ID:	14647
    As the date format is UK and month is in English, I'm guessing it got repaired here in the UK. I wonder if it's one that Sudesh in Northern Ireland did?

    Somebody on here must know!
    2005 NA2 NSX, Berlina Black with full red leather interior.
    2016 NC1 NSX, Casino White Pearl with red semi-aniline leather and alcantara.

  3. #3
    Join Date
    Jan 2018
    Location
    Near Stuttgart, Germany
    Posts
    246
    Blog Entries
    25

    Default

    Could be the case - nice analysis. The owner who bought the car around that year wasn't aware of it.
    1997 JDM Custom Order AT VIN 1400005 - Stock
    Heineken's Garage

  4. #4
    Join Date
    Apr 2004
    Location
    West Sussex
    Posts
    4,534

    Default

    I don't think Sudesh ever fixed anything like that. He just cleaned things and took 100's of photos!

    English spelling but European style number one maybe?

  5. #5
    Join Date
    Sep 2008
    Location
    Bucks, UK
    Posts
    2,231
    Blog Entries
    2683

    Default

    Quote Originally Posted by Heineken View Post
    ....
    ........
    ............
    A significant amount of time went into the analysis but the gained knowledge should come in handy for future repairs. The exchanged ICs (MC14066B and JRC2060) are still available, via the usual channels, btw.

    Timely post as just received another head unit for the refurbishment and while someone already serviced it, not in great shape.

    Very poor soldering method used and not cleaned thoroughly as seen in the above photo.

    This one is going to take a long time.....

    Different circuit board spec and can't even see the parts # on the IC but good to know these components are still available.

    Thank you for sharing.

    Kaz

  6. #6
    Join Date
    Jan 2018
    Location
    Near Stuttgart, Germany
    Posts
    246
    Blog Entries
    25

    Default

    Wow, just when I thought I had already seen PCBs in a bad state .. at least the affected area seem to be away from the non-standard parts.
    1997 JDM Custom Order AT VIN 1400005 - Stock
    Heineken's Garage

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •