Can anyone tell me how to bench test an am/fm radio?

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Can anyone tell me how to bench test an am/fm radio?

Postby 1p3bp » Sun Sep 10, 2017 3:56 am

I've bought an AM/FM radio off of Ebay for my 86 Reliant because it matches the one that came with it. I took the original out and had a radio shop repair it. It sat there for a month and I went to check on it. He said he couldn't fix it and gave it back to me in pieces and a newer Chrysler radio cd player which the cd player took forever to load and now has totally stopped working. I want to put the AM/FM back in I got off of Ebay but I would like to test it first before I tear the dash apart. I have a spare Optima battery in my Charger that's not currently being used. I've got the original rear speakers out of the Reliant. Now I just need to know how to hook it up to properly test it without causing damage to anything. I remember my original one's screen was going crazy but I believe the stations worked.
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Re: Can anyone tell me how to bench test an am/fm radio?

Postby Kwagon2 » Sun Sep 10, 2017 5:34 pm

Hi
Me Again.....I've tested a few of these after I patch 'em up and see if my repair worked ....I replace all of the electrolytic capacitors and they usually come back to life ...except for the radio from my Reliant ....couldn't save that one. You said you have the '86 Electrical manual ...there should be a wiring diagram showing the pin out of the connectors on the back of the radio
The eighties radios used a black and a gray connector both are seven pin ....just hook them up as per diagram . The 12 volt feeds etc. are identified with "X" designations in the manual so if you observe the pin out you shouldn't go wrong. I have a spare antenna mast that I plug in to the radio being tested , I run a grounding jumper between the "shell" or housing of the antenna (where it would normally be in contact with the car body) to the radio housing grounding stud and then to the battery negative. That's what I do .....
I've repaired a few erratic displays by simply re-soldering the connections to the circuit board .
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Re: Can anyone tell me how to bench test an am/fm radio?

Postby 1p3bp » Mon Sep 11, 2017 3:31 am

Oh I might need some more instruction on hooking it up and now I'm not sure if the Ebay one I got is the same as my 86 Reliant. My original AM/FM 86 Reliant radio has The Ebay one I got looks identical but the gray connector only has 4 pins. I'm guessing it was in a car with a mono speaker. If I remember right the gray connector is for the speakers. My 86 has 4 speakers which I just replaced with Metra OEM in the dash and Sound Extreme in the rear. It's been awhile but if I remember correctly the only thing wrong with my original 86 Reliant radio was the screen was wacky. I think I remember that it lit up but the numbers were going crazy. I believe the stations actually worked you just couldn't see where you were. So I've got it apart and I've got the screen board apart. I need to know what to look for that would cause the screen to do that if it's something that can be repaired. I remember I had screen that wasn't working on my Ford Ranger cd player and I took the screen board off and noticed that two of the LCD pins passing through the board had come off their solder so I soldered them back and it worked. Now on this 86 Reliant LCD screen board it looks very similar to the Ranger radio I worked on. There is 5 pins on the top of the LCD screen that don't have any solder on them at all but they also don't look like they're going to any circuit. So I'm not sure if that's how they are suppose to be. Any suggestions on what to check to repair the screen?
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Re: Can anyone tell me how to bench test an am/fm radio?

Postby Kwagon2 » Mon Sep 11, 2017 1:41 pm

Hi
I'm not sure about the radio you got from ebay...( is the model identification tag still on it?) Generally what I've seen is all electronically tuned Chrysler radios with a single gray connector (monaural) use six wires...two for the speaker and the other four for the supply and lighting control feeds.
On the circuit board of your Reliant radio check all of the pins coming from the top of the Vacuum Florescent display (its not LCD) to the board look for tiny hairline cracks right at the pin itself or look for a solder connection that has a grey crystalline look to it , thats a "cold" solder joint , resolder stuff like that. Also check the terminals where the ribbon connector comes into the board for the same thing. That's where I've found problems. The five terminals that have no solder on them and no circuit trace to them are normal....
If that doesn't do the trick then maybe the display driver is sick and requires replacement ....but parts??
So far I haven't been able to locate any parts as the chips are all proprietary as they have Chrysler part numbers on them so all that most likely went away when Huntsville closed. But I'm still looking.....
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Re: Can anyone tell me how to bench test an am/fm radio?

Postby 1p3bp » Mon Sep 11, 2017 8:03 pm

I was able to test the Ebay radio I got with a battery and I see the display is good as well as all the buttons. It does only have 4 pins on the gray connector though. It has the Chrysler sticker on top but the number is faded away. I have the old rear speakers out of my Reliant but the terminals are not marked positive or negative so how do I know which wire to connect where? And where to do I connect on the black connector and gray connector to use a speaker to test for sound? I'm wondering if I can swap out displays from this Ebay radio to my original since I know it's working right.
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Re: Can anyone tell me how to bench test an am/fm radio?

Postby Kwagon2 » Tue Sep 12, 2017 12:13 pm

HI
Speaker polarity is a relative thing and used for making sure the speakers are "in phase" meaning the cone moves out or in in unison etc. You can check speaker polarity by momentarily touching the terminals with a 1.5 volt battery and watching the speaker cone movement....once observed mark terminals accordingly.
So now I'm a bit confused...this ebay radio has both the gray and the black connector? Either way you'll need the pin out wiring diagram to hook it up.
As far as switching the displays ...I can't say if that would work , I've never played that kind of mix and match , the components would all have to be identical and removal from the donor radio would need to be done carefully .
However..... instead of going through the soldering and de-solding process on the components and risking damage to them something that could be tried is to check the part number on the front of the whole display board itself , if the "assembly" part number is the same (usually printed on the top edge of the board) chances are you might be able to just replace the entire board ....just a thought ...if it doesn't work I was never here.....
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Re: Can anyone tell me how to bench test an am/fm radio?

Postby 1p3bp » Tue Sep 12, 2017 3:44 pm

Well I went to test my original radio and since it was missing the cover I had it turned upside down. When I hooked up battery power to the gray connector something burned and started smoking. I think it's gone for good. Plus I took apart the ebay radio and although they look identical on the outside everything is different inside. I looked to see what pins weren't there on the ebay radio and it's the panel return pins and the mute pin. So it might work in my Reliant but I'm guessing only the rear speakers would work.
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