Getting no sound out of my stereo

Tiny
UDMAN2006
  • 1995 JEEP GRAND CHEROKEE
  • 202,000 MILES

I am getting no sound out of my factory Chrysler Infinity Gold cassette stereo system. The HU illuminates and is receiving power from both the 12V constant and switched circuits. I have a remote amplifier under the driver side rear seat and it too is receiving power. I have checked continuity of the wires leading to the amp and they are intact.

The speakers appear to be capable of functioning as I have hooked a power source to them and have heard the "pop" associated with functionality. I have checked continuity of the leads of the speakers and the connections and they appear intact.

I have checked the fuse :(#10 I believe) which is specific to the radio and it was fine. I swapped out the amplifier with one from the junkyard and the problem persists.

Please note that the power antenna has been snapped off and I cannot determine if the motor is operable or not. I can tell you that no sound is audible from the motor.

I appreciate, in advance, any help you can provide. Much thanks.

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Monday, December 10th, 2012 AT 2:23 PM

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Tiny
CARADIODOC
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Besides the 12 volt feed and ground wires to the amp, it has to receive the turn-on signal from the radio. That's the same wire that feeds the power antenna. With the radio still plugged in, use a jumper wire to connect either power wire to the turn-on wire. If the amp turns on, there is either a relay in the radio that has bad connections or a transistor circuit that has a problem, depending on the model number. The wires to connect are the one farthest away from the key way in the end of the black plug, to one of the two farthest away from the key way in the gray plug. I prefer using the second wire from the end since that's the main power wire and is on a larger fuse. (That's "Acc" to "Ant).

If that works, it might be less expensive to find a used radio in a salvage yard, but sooner or later they all develop the same problem. Once repaired, they're fixed for life because we use beefier parts. The radios for '93 - '95 Jeeps have different mounting ears than most other Chrysler radios. Those ears were also used in the late '90s Avenger but they had orange displays. Also, look for another Infinity radio. All Chrysler radios put out speaker-level output and will run the speakers directly without an amplifier. The Infinity radios put out much less bass, then it is made up in the amplifier for the shape of the vehicle. If you use a standard radio, you'll have too much bass unless you turn it way down.

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Monday, December 10th, 2012 AT 9:10 PM
Tiny
UDMAN2006
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Hello Caradiodoc,

I have tried the same suggestions you provided. When jumping either of the two power wires with the last connection on the black connector, no change occurs.

Please note that I have changed the problem radio with another stock radio from the junk yard and the issue remains.

I am thinking that it's a ground issue and that the inoperable antenna figures into this somehow. I removed the old radio and attempted to operate it externally. I hooked up my charger to the two power pins in the back and used alligator clips to the 1st and 5th pins to hook up a speaker I had laying around to see if it would play. Although no antenna was hooked up to it, I thought I would hear some type of static at the very least. Alas, no sound was forthcoming.

Any other suggestions or directions to provide me? I'm pretty good at following instructions.

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Tuesday, December 11th, 2012 AT 12:15 AM
Tiny
UDMAN2006
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Please note that no sound emanates from the speakers no matter which band nor function I attempt to use i.E. FM/AM or tape. Either there's a ground issue or the amp is not turning on. It might be because of a broken ground since I don't have power to the rear windows nor my horn or some other fuse related matter. I have checked Fuse #s 1, 4, 8, 10 and 24 and they all appear to be intact although I have not put a continuity test to them.

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Tuesday, December 11th, 2012 AT 12:24 AM
Tiny
CARADIODOC
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What happens if you try hooking the salvage yard radio ti the charger and speaker? What's the mode number on both radios?

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Tuesday, December 11th, 2012 AT 1:05 AM
Tiny
UDMAN2006
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I haven't done that yet, but I don't anticipate anything different. The model number of both radios is the same - 4704315. Would a broken wire in the driver side door cause any of this issue? If it were a ground wire?

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Tuesday, December 11th, 2012 AT 5:25 AM
Tiny
CARADIODOC
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No to both. The only wires between the door hinges are two for each speaker. If there's separate dash speakers, the left one would still work even if there was a broken wire to the door speaker.

There's no ground wire in the two connectors. The antenna shield, (the outer braided shield in the wire), will provide a ground but it's not a good one. There will be a flat braided ground strap or a black wire bolted to the back of the radio, or a black wire clipped to a stamped terminal on the back of the housing. If the ground was missing, the radio would be dead, including the display.

Lets go back to the basics. Measure the voltage on the "Ant" wire. There should be 12 volts there when the ignition switch and radio are turned on. If there is, find that same color wire at the amp and check for the same voltage there.

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Tuesday, December 11th, 2012 AT 6:25 AM
Tiny
UDMAN2006
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Ok, so it appears the both of the radios are bad. I jumped the power and the remote connections and the left side speaker and the front tweeters came alive. I then tried it on the salvage radio and the same situation.

Now this solves the great mystery, but I need to know my options. What would it cost to repair the radios at your shop or is it something I can accomplish with my limited soldering skills?

Additionally, I am concerned about the poor sound quality from the other speakers. As I moved the balance control to isolate the rear speakers, no sound could be heard emanating from the rear speakers and only faintly from the passenger front speaker. The tweeters in the front dash did not appear to be fully operational either. Is this a product of the radio issue i.E. Some of the channels going bad?

Appreciate all your help!

J

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Tuesday, December 11th, 2012 AT 6:59 PM
Tiny
CARADIODOC
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Well, the good news is there is no relay or turn-on circuitry in your radio. The switched 12 volts at the power antenna terminal comes straight off the power switch. I've repaired hundreds of arced switches years ago, but never one on your model. I'd find it odd for two of them to be causing a problem, let alone one.

There is a fuse resistor at the end of the 12 volt line after that supply has fed the output I.C.S and the other circuitry. My suspicion is something is shorted on the turn-on circuit in or to the amp and it burned that fuse resistor open. That would do the same thing to the replacement radio, which would explain why they both have the same problem.

Do these tests in the diagram below. Measure the continuity between the switched ignition wire and terminal 5 in the round cd changer socket. Don't ask me how they came up with that numbering but I drew the picture with pretty red and black meter leads to avoid confusion. You should find 0 ohms with the power switch turned on, plus the small normal resistance in the meter leads. This part of the circuit should be good, otherwise the radio wouldn't play at all.

Next, measure from pin 5 to the power antenna terminal as shown with the nifty blue meter lead. You should read 1.2 ohms plus the meter lead resistance. If it reads open, that fuse resistor is burned open. If that's the case, go to the black plug in the vehicle and read the resistance between that wire and ground. It should read very high or open. If it reads a relatively low value, read it again after you unplug the connector from the amplifier. If it still reads low, that wire has rubbed through the insulation and is shorted to the body. Gotta fix that. If it reads open now, something in the amp is shorted.

I don't have service manuals for most of the amplifiers but there's a good chance I can figure out the problem and fix it. It would be easier though to try to find another one in a salvage yard. If you're anywhere between Ohio and southern Georgia, there is a real nice chain of yards called "Pull-A-Part" where you pay your buck, throw your tool box in one of their wheel barrows, and you can spend all day there. I bought a lot of Chrysler amps from them including one to replace mine in my '93 Dynasty with only 4,200 miles. The turn-on circuitry failed on it too, I suspect from constantly disconnecting and reconnecting the battery. Those amps only cost me 18 bucks each. Finding one for my Dynasty was real hard because only about one car in a hundred came with the premium sound system. The Infinity system in your Jeep was real common so amps should be easy to find.

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Wednesday, December 12th, 2012 AT 12:57 AM
Tiny
UDMAN2006
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Hi Caradiodoc,

First of all, thank you for all your help. I assumed we had found the problem and it was two defective radios - what's the odds of that. Now, it appears what I always suspected - a short some where.

I am clear on all your instructions except as to how you want me to check the black wire. I assume you mean to check the ground wire connected separately to the large bolt on the back of the radio. I also assume that you want me to test continuity by touching one of the multimeter leads to that wire once disconnected from the back of the radio and the other lead to some known ground point i.E. The negative battery cable or seat bolt. If this is correct, please advise and I will do so straight away.

Please note that I have installed a salvage amp in place of the original amp as I thought it might be the problem as well. As such, I would find it quite odds-defying if both of the amps were defective - the same odds-defying chance that both radios had the same defect.

If there was a short some where, wouldn't the fuse blow or some noise indicative of this be heard upon connecting the radio or amp?

I'll get the other readings while I await your reply.

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Wednesday, December 12th, 2012 AT 2:19 AM
Tiny
CARADIODOC
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Don't worry about the ground wire. It has to be okay, otherwise the radio wouldn't even turn on.

If there is a short on the power antenna line, a fuse DID blow. That's the 1.2 ohm fuse resistor inside the radio. It is way at the end of the circuitry so even when it blows, the 12 volts will still get to the rest of the radio. The only place the voltage will be missing is at the power antenna terminal. That wouldn't even be noticed if the radios were used in a vehicle without a remote amp or power antenna.

If I recall correctly, you found no voltage at the power antenna terminal. I can't tell you how many times I've gone down the wrong road when troubleshooting a tv because I got an incorrect voltage or resistance reading, usually from a poor contact with the meter probe. That's why I'm having you do these resistance checks. They're just to double-check the previous findings and verify we're on the right track. We know the power switch has to be good because the radio turns on. If you don't get a near 0 ohm reading on the first test, we have to figure out what you're doing wrong before we move on to the second test.

I'm hoping you tell me you find an open circuit on the second test on both radios. If you do, the third test will determine if the wire or the amp is the problem.

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Wednesday, December 12th, 2012 AT 3:16 AM
Tiny
UDMAN2006
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Ok Caradiodoc,

I performed your aforementioned tests with the vehicle running and the radio connected to the wire harnesses. I inserted a wire into the pin hole number five and back probed the switched power wire with a piece of metal. I then checked continuity between those points and had none.

I then back probed the antenna wire and found complete continuity between pin connection #5 and the antenna wire. I then checked continuity between the black wire (while it was still attached to the radio) and ground and found a reading of 030. I did not test it again with the amp disconnected as of yet. I will do so tomorrow and perform any further tests as you direct.

Thanks again. I remain.

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Wednesday, December 12th, 2012 AT 5:52 AM
Tiny
CARADIODOC
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Whoa. Hold on. You can't do continuity checks with power applied to the circuit. Remove the radio from the car and unplug all the connectors. Forget about that ground wire. It's fine. With the radio on the bench, just measure the resistance between pin 5 in the round jack to the other two points. To the "Ign" terminal in the gray plug should read nearly 0 ohms when you turn on the radio's power switch. To the "power antenna" terminal it should read close to 0 ohms all the time, regardless of whether the power switch is on or off. That last measurement is the most important one to tell us where to go next.

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Wednesday, December 12th, 2012 AT 10:39 AM
Tiny
UDMAN2006
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Hi Caradiodoc,

Continuity exists between pin 5 and the remote/antenna wire. No continuity at all between the ACC/switched circuit and pin #5; the reading is very high. The testing was consistent across both radios.

Where do we go from here?

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Wednesday, December 12th, 2012 AT 7:37 PM
Tiny
CARADIODOC
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That would indicate both power switches are bad.

AGGGHHH! Stupid me. No wonder I can't remember working on one of these radios. What I was looking at as the power switch is not a switch. It's that relay I mentioned a while back. Those commonly develop bad solder connections. Of the over 200 radios I have here I don't have one like yours to look at so I have to do this from memory. There were three things I ran into very often. I think where I messed up is by having you jump the switched ignition wire to the power antenna wire. That would indeed bypass the relay and turn on the amp or power antenna, but there's additional circuitry that turns on electronically, not through that relay. Everything might have worked if you jumped those wires AND turned on the power switch. Can't say for sure though because the timing of those two things might be critical, and I never tried it.

You'll need to remove both covers, then remove four screws to allow you to lift the cassette mechanism out. Two screws on each side of the radio must be removed, then you can pry out the metal plate that sits right above the cassette mechanism. Once that plate is removed, you'll see the solder side of the circuit board. My sad drawing shows approximately where the relay sits. If there's numbers on the board, it's "K701". Look at the two left terminals to see if either one has a black ring around it like I tried to show with the red arrow. If either one looks bad, resolder both of them. If the cassette player became unplugged, you can leave it out and just plug the rest of the radio into the vehicle to try it.

That problem will cause no sound, even in vehicles that don't use a remote amp, and no switched power to the antenna or amp, but the rest of the radio may still tune stations, and the display will light up and the cassette player may still run. I can't remember for sure.

Next, look in the area of the blue arrow. There are about two dozen connections that become overheated and have to be resoldered but this is easier said than done. The new solder with its flux will not flow smoothly to make a nice shiny connection. I used to use solder wick, a special braided wire with flux in it, to remove the old solder, then the new solder flowed better. You have to be careful to not overheat those connections because most of them are for transistors. Transistors hate heat. If your soldering iron is adjustable, turn the temperature up high so you can get in and get it over with quickly. People think a lower temperature is safer but in fact, you have to sit on the connections longer to get the solder to flow smoothly, and that gives the heat time to migrate into the transistor.

Those intermittent connections cause the third problem. Some of them are in the memory circuit. They turn on two transistors in the "reset" circuit. Integrated circuits and their larger microprocessors have thousands of transistors built in that start out in random, disorganized states. They must be "reset" to their starting point as soon as power is applied. That means that reset circuit only operates when the radio is plugged in or when the battery is reconnected. It will not operate again for many years when the battery is disconnected and reconnected for some other service. The two transistors involved are only capable of passing a tiny fraction of an amp or they will overheat, but in this function they have to pass about 100 times what they're capable of, but only for a fraction of a second. It's like passing your hand through a torch flame. You can do that without injury if you're fast enough.

When the bad connections develop around that blue arrow, that circuitry can turn on and off intermittently multiple times per second as you're driving on rough roads. That mimics disconnecting and reconnecting the car's battery repeatedly, and each time it's reconnected, there's that surge of current through those transistors. Each time they heat up a little more with no time to cool down, and eventually they explode. Look on the other side of the board for "Q821" and "Q822". Hope you like green. That's what I used to show their locations. Each transistor is a small black cylinder with a flat spot and three leads. If all you see are the three wires sticking up, they've exploded. Generic replacements are not expensive. If these had failed, the radio would not turn on at all. You'd have no display, but it seems to me the cassette player would still run. It's hard not to get replacement transistors that are a lot beefier and hold up to those repeated surges better, and if someone replaced them already, they could look different. There's a lot of different shapes and sizes but they'll all have three leads.

As a side note not related to your radio, there is a newer model that had a 100 percent failure rate of that reset circuit. Since it's not needed once the microprocessor is running, it can fail and no one will ever know it until the battery is disconnected for some other service or it runs dead. Mechanics often have to disconnect the battery, then they get blamed unfairly for causing the radio to be dead. The problem actually occurred months or years earlier but only shows up when the battery is reconnected. I compare that to a starter motor falling off the engine while you're driving. You'll never know it until after you stop and try to restart the engine.

Anyhow, start with those tests. The fact that you have continuity from pin 5 to the power antenna wire proves the fusible resistors are okay and nothing is shorted in the amp or the wire going to it. I was thinking about relay connections but I failed to see all of that relay on the schematic diagram. I think I'll blame that on my aging eyes.

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Thursday, December 13th, 2012 AT 4:21 AM
Tiny
CARADIODOC
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Sorry. Dandy drawing didn't get included.

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Thursday, December 13th, 2012 AT 4:27 AM
Tiny
UDMAN2006
  • MEMBER

Alright Caradiodoc, I will attempt the brain surgery you suggest. Understand, however, that I have gotten another bone yard special and will be trying that one out today. This newest addition is one of those "good" Mitsubishi radios you spoke of earlier.

I also found frayed and broken wires in the harness that runs between the doors. I took out the old harness and replaced it with one from the boneyard. The donor car was a Grand Cherokee Limited from the same year. When I installed it the tweeters came alive with more power than before and the right rear speaker works. Unfortunately, the previously operable driver side front speaker and the windows failed to work. Not sure if this is a by-product of using different wire harness for different models.

I am going to repair the old harness - two black wires in the harness were frayed and partially cut - and reinstall it. The same issue is appearing on the passenger side as well.

Even if the problem exists in the radio, wire harnesses or some combination thereof, I will be attempting the brain surgery just because. LOL.

I'll keep you posted on my progress.

John

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Saturday, December 15th, 2012 AT 2:40 PM
Tiny
UDMAN2006
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Ok Caradiodoc,

I hooked up the Misubishi radio from the salvage yard and it illuminated, but did not power the speakers. Unlike the others, however, the display would change from clock to station frequency with a symbol indicating it was in tape mode. Also unlike the others, I have power at the antenna connection.

Using a jumper wire, I can get the other radios to power the tweeters, but not the speakers. I believe the speakers aren't powering because of the issue with the wires in the door.

I do believe I have the misfortune of finding two radios with internal issues. I don't believe its entirely the wiring. I am not sure if the Mitsubishi radio is also defective since it's acting differently than the others.

Any further help would be greatly appreciated.

John

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Saturday, December 15th, 2012 AT 7:04 PM
Tiny
CARADIODOC
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(I'm just leaving to help a friend out-of-town troubleshoot an intermittent electrical problem so I'll be gone for quite a while).

If you have the cd / cassette combo, the only thing that I can think of that would cause it to have no sound is intermittent FM. Once fixed, that is fixed for life, but you will still have sound on AM, tape, and cd.

Given the variety of problems, I wonder if a pair of wires shorted together between the door hinges is causing a protection circuit to kick in. Some radios have a speaker protection circuit that detects a speaker wire shorted to ground and will shut the audio output system down to protect the output ICs. One inexpensive cassette radio will display "SPKR" instead of the clock, and the shorted wire will partially bypass the protection circuit so you'll have no sound from the good channels and weak sound from the speaker with the shorted wire. Some of the higher-end radios just shut the entire audio system down, and some just turn off the affected channel.

I never really got involved with shorted wiring because other mechanics handled stuff like that. I just got handed radios to take home to fix, and there's no shorted wires on my test benches. You might try disconnecting the harnesses from the "A" pillar by the hinges, then turn the radio off and back on to see if the other speakers come back to life.

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Saturday, December 15th, 2012 AT 10:10 PM
Tiny
NCC74656-A
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Sorry to resurrect an old thread, but I am having a similar issue.

Got a 1998 GC to replace my 1993, and found the radio only works on the fromt left speakers. After some "fiddling", I got the front right to work, but it will go out of I turn up the volume.

The front harness is stock and connected. The HU is stock (CD/Cass). The wires to the front right seem to be intact, but there was a Pioneer speaker there. My first test was to replace it with an infinity speaker from my 1993. Both speakers exhibit the exact same issues, so I'm ruling out a bad speaker.

When the front right goes out, it gets very distorted with increased volume, then the audio shuts down completely on that speaker only (front left stats playing).

Add to this the rear speakers which I haven't tried replacing yet, but I suspect the issue might be the amp, and failing PA transistors in it.

I would like some expert guidance. Since the front left speaker is working, I'm assuming (yes, I know) that the amp is getting power, and the head unit is keying it on. If I unplug it, I hear a power-down whine from the amp. Also, if I plug it in while the radio is powered, often the missing audio on the front right will return (hence my belief that a PA is failing). I have not had time to ring out the wires to confirm continuity, nor to check the amp voltages.

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Tuesday, July 28th, 2015 AT 5:57 PM
Tiny
NCC74656-A
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Sorry for the typos in the above post. Fromt=front // "of I turn up the volume" should be IF I turn it up.

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Tuesday, July 28th, 2015 AT 5:59 PM

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