If you mean the 'original' radio, thats amazing. Still blows my mind that i can't seem to find even a bad picture of one like mine anywhere on the internet. Even looking through all sorts of junkyard pics at the dashes on car-parts.com got none.


Modern is nice and all but i hate the way they look (and don't fit). I even didn't like the donor radio because it had stupid yellow lights (everything else in the truck is the green shade) on the balance *****. Turns out when taking it apart to fix the volume dial they have a slotted LED inside the slider and you can just pull them out. So that part is 'fixed' (as well as the volume ****). So now the donor radio is back to its donation status where CD doesn't work. That still is sort of an issue as i was planning on putting a bluetooth module in the CD left/right line to play off my phone, but it won't play CDs so that won't work yet. Just says ERR when you try and then spits out the CD. It does seem take in and eject CDs fine, the other motors all seem to run when you put power to them, so not sure whats wrong, other than the underwater thing. Again i don't know much about CD players just like i don't know much about radios, but basic electronics i can do.

For fixing the other radio, i haven't really done anything other than continue looking around for any chance of finding the original with no luck. It has had some interesting effects though. I have seen 2 different AM/FM only radios with a face more like mine. One that is clearly like a cassette version without the cassette slot. No Cassette Another that seems to be even more like mine without the CD slot. No CD That one is very interesting as the connector layout looks identical to mine, so there is a good chance its whole radio board is the same as mine... might just have to get it and see if i can fix the radio of the original with it. Still would be a gamble as it could be they are not at all alike inside and technically i don't have any idea why the original radio tuner doesn't tune. Replacing parts at random isn't a great idea, but if they were identical it would at least be possible. And it could also be possible to do some basic voltage tests on identical boards to see if there is something simple wrong that i do understand.

Not sure what to do next, as i am still wanting to 'modernize' the thing a tiny bit with the bluetooth module but a working radio for when too lazy to use the phone is still necessary to me, so both my radios still are only half there. And yeah, i know there are ready made modified version of the donor style with AM/FM cassette and CD usually, but that is a little silly first to pay that much and to add a cassette slot for no reason. Fixing the CD player is probably easier, as i could get a maybe working radio like my donor one off ebay right now and combine the best parts of each. But the original is so unique (it appears) that it almost seems wrong to not try and get that one back to life.

 

It should have a OE part # on it, Try using it to search.

 

Hey, Gorgok.

Last week I forgot to mention to you that the same source also repairs what you might want to keep.

https://www.mnrelectronics.com/factory-radio-repair/

Email them, you might get happy!

 

So I copied them to my phone; now playable via YouTube Music app + BT cassette adapter.

 

Might want to call and speak with this guy to see if your unit can be repaired and/or retrofitted with desired upgrades - He comes to the Chryslers @ Carlisle, PA show & swap meet every year in July (this year on the weekend of July 14th) marketing his services - https://retroradio.biz/radio-restoration/

 

Later on this year i going to pull the dash out and replace just about anything that can give problems and replace the dash ect . So if you still need on i give you mine . It works ok . Seems its cd and cassette. I never use it .

 

I saw a cheap no CD version of my radio on ebay and put a bid on it, winning it at ~30 shipped. And its incredibly clean for something with chips dating from 94. I mean none of the buttons look like they have ever been pressed. And getting it is on a hope of still fixing my original because i can now compare it to this one. And for the most part i think i probably could do some compare/contrast on it, if i knew more of the signal path and such (i really wish datasheets for these chips existed), but need more knowledge first. Anyway, this is the face.

Face of no CD radio

Here are the topside board shots of the original with CD board and the 'new' no CD board. There are lots of differences, unfortunately; it wasn't just some unpopulated chips and such for a board lacking CD features. But, it also looks similar enough on the left to bottom left, where the whole tuner sections are (as best i understand). Now i just need to figure out useful tests to run.

Original board

No CD board

Tuner cans of the two boards seem to be identical. Not sure if just straight out swapping them would be enough to fix the issue, as i don't know how much it relies on the adjustable thingies near it to be tweaked just right... Plus i still don't know if its broken.

No CD tuner(?)

Original tuner(?)

Now now i have 3 old radios, yay! (I know there is probably something wrong with me, heh) And seeing how clean this sucker is i have had another thought. What if i were to intercept the AM left/right channels instead of the CD left/right and just stick the mod into this radio? Its as pretty if not prettier than the original. Its also kinda quirky, and so far all the googling on fixing FM has been not too great sounding even with very similar boards. End result would ideally be that hitting the AM/FM button would flip from bluetooth to FM instead... Just would need to figure out where to do it (i assume it would be before a mux chip). More pondering to do, this being a very back burner project and all more for fun than actual necessity (i did fix the donor radio enough to be my radio a while back after all).

 

That radio you got was probably pulled and replaced with a nice aftermarket unit 6 months after the original owner got it.

 

Here is the picture of my radio in the truck. Mine has the cassette and CD. There are some with car-part.com

 

Bunch of progress, and mostly a success. There is still a noise from the bluetooth signal at higher volumes that i'm not sure how to kill. Basically as long as the module is powered the input cable is enough of an antenna that it picks something up even when the cable isn't plugged into the module. And powering the module separately didn't seem to help either... I haven't tested it on a drive yet, with the background 'hum' of the Cummins, so not sure if i really need to dig deeper.

First i traced out a bunch of the board to try and narrow down where 'sound' was coming from and going to until i hit some chips. Starting from the outputs and the output amps it was simple enough to hit the first real IC, which all have custom names annoyingly. But enough googling makes it appear to be a TDA7314, an audio processor for balance/fade and EQ stuff, and the pins matched datasheet to my board. That got me more pins to trace for stereo inputs. Those pins went off to an IC i think is a TDA1591, a stereo decoder that does AM mono to stereo also. Which is one of those things i didn't even think about, AM is sometimes mono... So my latest plan of stuffing stereo in on the AM lines sort of fell apart there. But i had already traced some of the AM tuner (LA1137N) side out too, just slighly confused on the single 'out' line which made more sense now. Used paint as my awesome drawing tool. One of the faces of the board is mirrored to make lining up the two sides easier.


With this knowledge in hand i wired up the module output directly to the output of the stereo decoder thing, and put 5V on the mute pin of the AM tuner to make it shut up always. I stole power from the AM tuner ~9V supply, which only is on while the AM range is selected. And it was horrible. All the volume from the phone and the radio and it would make some recognizable noise, but barely and badly. Sucks to only be able to test in the car, but out it came again.


I read the datasheet on the stereo decoder again and saw a test circuit where they had Aux inputs. Read some more and they mentioned using the chip auxiliary inputs for cassette etc. I looked more closely at the board and sure enough it was almost wired for aux inputs already. There were 2 47k ohm (based on the datasheet) resistor spots not populated on a path to that blank silk screened box on the top side (probably for a ribbon cable to a CD/cassette in another model). I got some resistors, plopped them in, rewired the module to the ribbon cable spots and it was much better, but very quiet and there is still some noise. I didn't want the volume to be drastically different from bluetooth to FM so flipping through would be annoying/scary so i figured whats the worst that could happen if i changed the resistor values. Half was better, half of that much better but the phone volume still has to be maxed, and half of that (4.7k) lets me set the phone volume down some and fine tune to match the FM. But for some reason the mute no longer seems to work?


Just remove this, no more AM sounds. Then i can remove the 5V off the mute too. Still bluetooth noise at higher volumes, only really noticeable between tracks obviously, but kinda annoying.


More poking around, testing various things, i end up changing the ground point for the power which helps a ton. Also changed the source point a little just to be closer to the ground (they share a cap now i think). Removed the direct solder audio source for a socket that came with the module just for neatness. Moved the module itself outside the radio in the hopes of less noise (didn't really help) but no longer plan to put it back inside anyway. There is still bluetooth noise on the AM side, more when its using data, noticeable when playing music at 0 phone volume or between tracks. Need to test in drive and see if its good enough or do i need to learn more about RF noise on analog audio sources. Or maybe i need to add those 220nF caps inline on the audio source like the datasheet said (though the board wasn't wired up for them, assumed they weren't that important).


Here is the datasheet test board. The two 220nf caps right at the aux in might help? Might just put them in anyway since i doubt it can be worse. But then again my resistor values are 1/10th of what they have to sound right.