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I have a delco unit on my bench out of an 89 firebird without 5-band EQ. Everything works except for the backlight and the clock. The display itself works perfect, but the clock doesn't... I cannot set the time, I can press the SET and SEEK buttons like crazy and just nothing happens. And it says always 1:00, the clock doesn't run... like an old watch with a dead battery... That never happened to me before. The illumination also doesn't work. It dims the display when I switch on the lights but the background illumination behind the faceplate is dead. I swapped the press in bulb in the amp and verified it works and when I give it 12 volt directly it lights up. My test-bench works, I have a couple delco units on my bench and the illumination works on all of them so the culprit must be in this unit. Anyone has a hint what to do? I have rebuilt a few amps and cassete players in these units but this is very strange.
I will take a pic of the radio in a few hours so you guys know what I am dealing with here.
Posting a pic of the radio ( front and back ) is a good idea.
I know there is a transistor (?) in the 85-90 radios that causes the clock to malfunction, but don't know it it would cause the clock to always read 1:00.
Edit: All the issues you describe ( Clock, Seek, Scan, and back-lighting ) are controlled by the middle circuit board,... might just have a bad board.
This is the radio I'm talking about. I've already replaced all six caps for the right and left channel (Fader and bias caps) and all four gain coupling caps because all of them leaked. I measured all traces for continuity, all came out good, there was also no visible acid on the board, just on the contacts from the caps.
Originally Posted by John in RI
Edit: All the issues you describe ( Clock, Seek, Scan, and back-lighting ) are controlled by the middle circuit board,... might just have a bad board.
Interesting... what do you mean by middle circuit board? The board under the radio board?
The clock/constant power and the dim illumination power go to the two pins I've highlighted on your radio picture, below: yellow(clock/constant, 1st/bottom pin), orange(dim illumination, 5th pin up).
And this is the adapter harness I have for installing a late-3rdgen/4thgen radio into my 87. The yellow and orange wires provide the constant power to the clock and the dim illumination power to the radio, as I marked on your picture. And in this picture, I've clocked the connector to the correct position to plug into the radio in your picture, matching the highlights I added to your picture.
So for simple troubleshooting, since those are the functions you're having issues with, is your test harness connecting the appropriate wires to the appropriate pins?
I doubt your radio is from an 89; the reason I say that is because you'll notice that the face-plate shows SEEK UP & SEEK DOWN. The 89 radio should have SEEK and SCAN,...... pretty sure the SEEK UP/DOWN began around 91. ( I COULD BE WRONG ! ) It's possible that the radio is originally from something other than a Firebird.
LAFireboyd; You're kinda' right, but not 'exactly'. That adapters 2 wire plug showing ORANGE and YELLOW would be ORANGE and BROWN on the factory harness. ORANGE = full time power for clock and station memory, but BROWN is a signal wire to indicate the headlights / park lights are on ( DIMs the display ). The variable voltage for the back-lighting runs on the GREY wire on the factory harness.
Another "funny" thing": If you inspect the adapter connector that is plictured close you'll notice that the adapters wire colors are all screwed-up and do not match a factory Thirdgen harness. It's ORANGE wire should actually be BROWN on a factory Thirdgen harness and it's YELLOW wire is where the ORANGE wire is positioned on the factory Thirdgen harness.
Back to the backlighting: might not help with your clock problem, but if this radio was original to a Grand Prix or Bonneville than you *might* need a 4th connector on back to get your back-lighting to work. Some cars used a 4th plug ( 7-PIN) for backlighting. All the radios in the next pic ( Buick, Olds, & Pontiac ) require a 4th plug.
GREY wire = center terminal ( variable backlight voltage )
BLACK = far LEFT terminal looking at back of the plug; LOCKING TAB UP ( backlight ground )
LAFireboyd; You're kinda' right, but not 'exactly'. That adapters 2 wire plug showing ORANGE and YELLOW would be ORANGE and BROWN on the factory harness. ORANGE = full time power for clock and station memory, but BROWN is a signal wire to indicate the headlights / park lights are on ( DIMs the display ). The variable voltage for the back-lighting runs on the GREY wire on the factory harness.
Another "funny" thing": If you inspect the adapter connector that is plictured close you'll notice that the adapters wire colors are all screwed-up and do not match a factory Thirdgen harness. It's ORANGE wire should actually be BROWN on a factory Thirdgen harness and it's YELLOW wire is where the ORANGE wire is positioned on the factory Thirdgen harness.
I almost addressed the wire colors because I knew someone would mention it lol, but to keep my post brief, I highlighted the pin positions in the radio, and the wire positions in the harness, to show how each related to clock power and illumination power. As for those wire colors not matching the car's harness, that's simply how the adapter harness comes.
But yes, the car has orange and brown wires for these features: harness's yellow wire to car's orange; harness's orange wire to the car's brown wire. Besides, it's the wire that carries the current, not the insulation color. So as long as each wire connects to the correct pin, and these do(they're also labeled accordingly, too), then the colors in the adapter harness are irrelevant. What's relevant is that the 4thgen radio works as it's supposed to in my 87 with this adapter harness.
So, again, just pointing out the pin positions to power those functions. Hopefully JC just wasn't getting power to those pins, which would indicate that the problem probably isn't internal.
Thank you all! The radio ist definitely an 89 model but I don't know for sure if it was originally meant to be in a 3rd gen. A buddy took it out of a 89 2.8 V6 parts car.
@LAFireboyd : My test harness is wired correctly. I double checked this yesterday again because I thought it might be a bad solder joint in my home-built harness. I then checked it with a 91 radio and everything works correctly on this unit.
@John in RI : I know these 4th plug units... I had some bad issues with the backlighting on one of these buick units, I saw your pics in an older thread where you had the same problem with non-working back lighting and they helped me a lot. But internally in my actual head unit here there is no sign of another connector that might be needed.
Just to mention, i tested the bulbs with external 12 volt source at the bulb directly and they work. The problem must be between the harness connector and the bulbs. Maybe I have to take apart the radio and trace the issue down by measuring voltage step by step. Maybe the illumination problem and the clock problem are related. I have a friend that wanted to buy this radio from me and now this...
05-17-2021, 09:54 AM
