I have a truck I inherited from my late brother, and he was big into car audio, having worked in the 1980s as a professional installer for a while. He installed an Alpine CDA-7838 Receiver/CD player in it, but it's got some issues. I do electronics repair work, so I'm just hoping to get pointed in the right direction since I have little experience with these. This is a unit with a removable faceplate. In general, it works fine, but it has some glitches.
Sometimes if I go over a bump, the whole unit will reset, and I'll lose all the radio station and time settings. I've checked the power supply, ground, and plug connections, and they seem to be clean and tight.
The lighting of the control buttons is flaky. Sometimes the buttons are lit. Sometimes they aren't. According to the manual, there are no controls for the lighting, so it seems like they should always be on.
Are there any known issues with Alpine units of this era? I'm thinking cracked solder joints. Should I look first in the main unit, or in the faceplate?
Sometimes if I go over a bump, the whole unit will reset, and I'll lose all the radio station and time settings. I've checked the power supply, ground, and plug connections, and they seem to be clean and tight.
The lighting of the control buttons is flaky. Sometimes the buttons are lit. Sometimes they aren't. According to the manual, there are no controls for the lighting, so it seems like they should always be on.
Are there any known issues with Alpine units of this era? I'm thinking cracked solder joints. Should I look first in the main unit, or in the faceplate?
I haven't tried it on the bench yet, partly because I almost exclusively work on things that run on 120VAC, so I don't have a setup in place to power a car stereo on the bench. And I'd need a connector to plug into the unit, a connector I don't have. I could rig something up, but that would be likely to get disconnected itself if I bumped the unit hard enough to replicate the problem. It needs a pretty hard bump to reset.
I tried that in the car a few days ago, and it didn't lose memory. But I'm not sure I bumped it hard enough. As is often the case with intermittent stuff, it seems to require just the right set of circumstances to go wrong. I moved the wires all around, too, and that didn't cause it to lose power or reset.
There is also the case of the illumination of the control buttons. That's not linked to bumps. It goes on and off at random.
There is also the case of the illumination of the control buttons. That's not linked to bumps. It goes on and off at random.
Is there a ribbon cable between the head unit main board and the faceplate or is it connected with metal contacts?
I'd try heating and cooling the internal components (CD mechanism removed) to see if you can find an area of the board that causes it to reset. You could also try twisting the body of the head unit to see if that makes a difference.
I'd try heating and cooling the internal components (CD mechanism removed) to see if you can find an area of the board that causes it to reset. You could also try twisting the body of the head unit to see if that makes a difference.
I have an update. I decided to take off part of the dashboard and trace the ground connection. I felt like it wasn't mechanically the best setup, so I ran a new ground wire and ring terminal secured with an external tooth lockwasher for good bite. Thus far, no more resets, so I think I may have solved that problem.
The faceplate mates to the head unit with gold-plated metal contacts. The contacts look to be in like-new condition. I swabbed them with DeOxit. But I'm still getting the control backlights coming in and out. (The main display always works.)
The faceplate backlights will go on and off with the car parked running on battery, and they go on/off on a long cycle. They'll be on steadily for a couple of minutes, then go out for a minute or two. A couple of times, I've gotten them to come back on by tapping on the faceplate, but it doesn't always work. The backlights are not that huge a deal, but it makes it hard to use it at night.
The faceplate mates to the head unit with gold-plated metal contacts. The contacts look to be in like-new condition. I swabbed them with DeOxit. But I'm still getting the control backlights coming in and out. (The main display always works.)
The faceplate backlights will go on and off with the car parked running on battery, and they go on/off on a long cycle. They'll be on steadily for a couple of minutes, then go out for a minute or two. A couple of times, I've gotten them to come back on by tapping on the faceplate, but it doesn't always work. The backlights are not that huge a deal, but it makes it hard to use it at night.
Most all of the Japanese manufacturers produce service manuals for all of their products. Many can be found for free (virtually no one here is willing to pay for one) but I couldn't find a free one for this piece.
https://www.servicemanuals.net/en/ALPINE-CDA7838-Service-Manual
This ^^ is likely a scan (non-searchable). An original may be available from Alpine or PacParts.
https://www.servicemanuals.net/en/ALPINE-CDA7838-Service-Manual
This ^^ is likely a scan (non-searchable). An original may be available from Alpine or PacParts.
Alpine basically laughed at me when I sent them a service manual request, so I bit the bullet and bought it.
Looks like the pilot lamps may in fact be small incandescent lamps that operate from the same +8V supply as some of the LED indicators. All of these pilot lamps and indicator LEDs go dark at the same time, so that points to a problem with that common supply.
The LCD backlighting is powered from a different faceplate contact, and it is not affected by this problem. All these lighting circuits share a common ground.
Maybe a first thing to do would be to open the faceplate and see if I see any cracked solder joints, starting with where the contacts join the PCB. That's a common spot for cracks in lots of gear.
Also, interestingly, the service manual is honest about the power output: 16W/channel into 4 Ohms (4 channels). Alpine's marketing was 40W "max" per channel. I suspected that was nonsense, but I thought consumer regulatory agencies had cracked down on bogus power specs like that by the 1990s.
Looks like the pilot lamps may in fact be small incandescent lamps that operate from the same +8V supply as some of the LED indicators. All of these pilot lamps and indicator LEDs go dark at the same time, so that points to a problem with that common supply.
The LCD backlighting is powered from a different faceplate contact, and it is not affected by this problem. All these lighting circuits share a common ground.
Maybe a first thing to do would be to open the faceplate and see if I see any cracked solder joints, starting with where the contacts join the PCB. That's a common spot for cracks in lots of gear.
Also, interestingly, the service manual is honest about the power output: 16W/channel into 4 Ohms (4 channels). Alpine's marketing was 40W "max" per channel. I suspected that was nonsense, but I thought consumer regulatory agencies had cracked down on bogus power specs like that by the 1990s.
I will look at the ribbon cable if I have to go into the head. According to the schematic, there is also a 24 Ohm 2W resistor in series with the supply node for these lights, dropping 12V to 8V. As I'm sure you know, the heat can cook solder pads, and/or the weight of a larger resistor can crack solder joints if not carefully mounted. The 12V supply involved also operates other circuits, and there is no indication they are operating intermittently.
May be a few days until I can get inside.
May be a few days until I can get inside.