help with factory 1992 radio/EQ

Discussion in 'Audio + Electronics' started by unruhjonny, Mar 21, 2020.

  1. unruhjonny

    unruhjonny Newbie

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    Help!

    (quick version)

    I have an issue and I don't know for sure the cause;

    My stereo's five band equalizer deosn't show anything other than the end range settings.

    Can someon help me figure out if this is an equalizer issue, or stereo/wiring issue?


    (longer version)

    I aspire to keep my truck appearing bone stock, and to that end I actually had a very successful pick 'n pull run;
    I purchased all the following as replacements:
    - Radio
    - cassette w/ 5 band equalizer
    - hvac
    I bought units that appear to be dead ringers of the ones currently in the truck;
    I think that the sun from the last number of years of street parking under my cousin's ownership caused all the grey buttons to start to delaminate - they look rather awful.

    Anyway, I had thought that the equalizer in the truck had a issue because only the far end settings could be adjusted;
    but(!) I do have a speaker problem - most of the time the passenger side speakers don't function right now - they occasionally cut in, but then will cut back out;
    I have figured that this was purely a speaker problem, as everything is factory issue in the truck at the moment.

    I plugged in the replacement units, and it looks exactly the same as the factory units;

    Am I missing something?

    Is what I'm seeing an indication of a wiring/speaker issue??
    (I sure am glad I didn't pull my dash apart to replace these before I saw this)

    [​IMG]

    Help!
     
    Last edited: Mar 21, 2020
  2. unruhjonny

    unruhjonny Newbie

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    So does nobody know what to make of this then?
     
  3. Eveready

    Eveready I'm Awesome

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    Two things can crap out on old electronics (well more than two but these two especially) . Capacitors (electrolytic) and potentiometers (sliders) . Replacements with similar values for the first and a nice bath in DeOxit contact cleaner will sometimes get the pots to work better. I suspect the latter is your problem with the EQ. The pot has been used most in its mid-range and is more worn and oxidized there. It functions at the extreme because it has not had as much use or wear there. Try getting a can of DeOxit (no I have no stock in the company) and see if that works. I did have some success once using it with a GMT 400 radio that refused to tune or change volume. Good Luck. There are some aftermarket radios that look exactly like the original if that is what you must have. Prepare to spend money if you go that route.
     
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  4. DerekTheGreat

    DerekTheGreat I'm Awesome

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    What pots? That means Potentiometer where my mind comes from, think JBL L150A, those things had pots for the midrange and tweeter- dials which were subject to corrosion and could definitely be helped by DeOxit. These digital things? At best you could do what I did with my old Nintendo controllers; get the apart such that you peeled the buttons off the circuit board, clean the black pad things and the area they make contact with using rubbing alcohol. I doubt that'll cure the display issue on the equalizer.

    You could indeed try to replace the capacitors, too much work for my lazy ass. I'd rather just try swapping in a new amp/brain section (the thing just above and in front of the gas pedal) and see if that makes the rest of the stuff work. Make sure it comes from another truck factory equipped with an equalizer. Bonus if you get one from '92 and up- they play better with lower impedance speakers.

    Having the wrong amp section already in place could be the issue with the equalizer- I've heard there are two types- one made for the Bass/Treble radios and one made for the five band equalizer units. I've never tried mixing and matching to see what happens but other members have said that if you stab a Bass/Treble unit into a five band equalizer set up, you'll only be able to control two of the five bands...
     
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  5. unruhjonny

    unruhjonny Newbie

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    I was laying awake this morning, wondering if the radio controller (aka "brain") might indeed be the issue;
    here's why:
    1) I have not known speakers to simply cut out, if they are wired, even blown speakers will make noise, it will be an aweful rendition of the intended noise, but it will make some noise in the least
    2) it's as though the EQ simply isn't receiving information from the computer to set those bandwidths.

    I will reach out to my cousin to see if by chance he swapped the radio controller, then dig a bit more on how to properly diagnose this.

    PS - I was prompted to come here by a facebook group, but it seems like activity isn't what I had hoped;
    are there any busier forums for our trucks?
    Just curious.
     
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  6. man-a-fre

    man-a-fre Newbie

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    Has the amp box (cdm)ever been changed? If so it may have been replaced with one that was not intended for a eq. I did this and my eq lit up the same as yours,i got a known eq cdm and everything worked great all lit up properly.I believe your cdm amp is for a non eq system.
     
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  7. unruhjonny

    unruhjonny Newbie

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    /\ might you have a part number for the correct versus wrong one?
     
  8. man-a-fre

    man-a-fre Newbie

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    Man,Theres alot of different part numbers that will work and alot that wont without removing mine i cant see the part number but ebay will have a few part numbers sorted out for you.You could also google k1500 cdm or something like that for info.I am pretty sure that is your problem though because mine did the same thing just the 2 outer lights on eq lit up with non eq cdm.
     
    Last edited: Mar 23, 2020
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  9. DavidAlan

    DavidAlan Newbie

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    https://www.google.com/search?q=cas...1.69i57j33.31846j1j8&sourceid=chrome&ie=UTF-8

    Iam kind of a guy who researches before buying or work with what I have,the truck I drive is also a 1992 ,but where I live,its being being piece mealed back together,I dont have that radio in my truck,but I looked up on the internet and found all sort of stuff for it,I have huge data base on chevy trucks,over the years have driven from 1967 to 1992 ,I believe there is no dumb question or answer when it comes to our babies,there are many companies out there that will gladly help you rebuild your radio orr anything else for that matter.
     
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  10. PlayingWithTBI

    PlayingWithTBI Desert Old Guy

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    If you find one, let us know. I'm a member in 4 forums and find this one to be the most active and germane to our GMT400s. There's a lot of useful info here, just spend some time looking around in this site, pretty much everything is here, just gotta find it...
     
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