Alpine 7525 car stereo

[Philpc]

I have an Alpine 7525 stereo that looks perfect in our 87 Volvo 250. It has stopped powering on and am wondering what type of component would be shot to cause this. It's not the car as another stereo works fine in the car. And there is an in line fuse that I tested and it's fine And I also bench tested the unit by connecting wires directly to a car battery and still didn't power on.
So any ideas of what to address are appreciated
thanks

[Andrew F. Ali]

Re: Alpine 7525 car stereo

look at the underside of the circuit board for any burnt out copper tracing. You would have to do some dismantling, though. Trace the +12V entry point on the board and see where it is lost. If your system is one with the three connections: +12V to Battery, 12V V on/off and Gnd. Check the 12Von/off line and it will go to a transistor than could be open circuit.

[Philpc]

Re: Alpine 7525 car stereo

Haven't gotten that far but upon opening the unit I see 2 suspicious looking capacitors; I assume the two with "goo" at their base are shot. Is that correct? It's the first time I've seen any like that.Here's picture.
When I look them up on the schematics they are in the pre-amp/amp part of the system so makes me wonder if they're the culprit.
The screwdriver points to the "stuff".Any help is appreciated.

thanks

[stj]

Re: Alpine 7525 car stereo

that's glue, and those are related to the speaker outputs.

what's the part number on the amp chip?

[tibimakai]

Re: Alpine 7525 car stereo

It may have internal surface mount fuse also.
You will need to take good quality pictures of the internals to get more help.

[budm]

Re: Alpine 7525 car stereo

How about posting the schematic you have?

[Philpc]

Re: Alpine 7525 car stereo

Will scan that part of the schematics.But for now I have a more immediate problem. How do I get this particular screw between the board and case out?. It will not budge and I have found at least one holding the tape player on the board that is troublesome. If I can't get these out the rest is moot.
thanks again

[momaka]

Re: Alpine 7525 car stereo

Try posting a picture of the entire unit. There may be another fuse or fuses inside the stereo. The pictures would also give us an idea of where to tell you to look for signs of trouble.

[Philpc]

Re: Alpine 7525 car stereo

Here are some pics. Will post the schematic after I get my scanner working(having a problem with windows drivers.ugh!)
thanks again for any help

[momaka]

Re: Alpine 7525 car stereo

Sorry to be such a downer, but the pictures are still from a bit too close so it's hard to tell how the boards connect and where power comes from.

On the second picture, IMG_0300[1].jpg, there's possibly a thermal fuse - TH001. Measure its resistance to see if it's good. Should be very low - a few Ohms, if even that (depends on how low your multimeter can read too). Post back what results you get.

Q811 (second to last pictures) also appears to have been running a bit warm - though it could be just the way the shadows appeared in the picture. And there still should be a fuse somewhere on the board. I doubt that little thermal fuse is all the board has. Perhaps there is also an enable/sleep signal on the harness? Check with the schematic.

And check all solder joints thoroughly.

[stj]

Re: Alpine 7525 car stereo

this is probably the same base pcb.
start with pages 6a/b