Car radio stopped working

[eccerr0r]

Strange... With the hot weather, suddenly my car's broadcast receiver stopped working. It had been working fine. I hear noise only when I turn up the volume all the way. I can "tune" but the noise silencer silences the noise after a second...

Cassette player still works.

Antenna failure, frontend RF amplifier failure, dunno yet, I haven't pulled the head unit from the vehicle yet...

Hmm.

[stj]

Re: Car radio stopped working

maybe there is nothing on air?
or your antenna is unplugged or damaged

[eccerr0r]

Re: Car radio stopped working

Damn. wasn't as simple as a disconnected antenna. Wonder if this 1995 radio has electronic or switch switching of audio vs cassette...

Wonder how much effort I should try to fix this or find another one from a boneyard.

[eccerr0r]

Re: Car radio stopped working

Ugh. Custom components, this is going nowhere fast. Some people have reported reflowing repairing the radios but I chalk that up to dumb luck... heck I wonder if I buttoned the radio back up without doing anything, it'd start working again...

[petehall347]

Re: Car radio stopped working

check antenna connections . might have corrosion where it connects to the body .

[eccerr0r]

Re: Car radio stopped working

AM works, FM does not work. Tuner problem. Has COB's. Probably lost cause.

[eccerr0r]

Re: Car radio stopped working

Thinking for now I should jury rig a line-in so I can at least use the PA, but probably will need to replace. Now figuring out where to tap in...

[stj]

Re: Car radio stopped working

is it DIN format, or some custom face shape?

[eccerr0r]

Re: Car radio stopped working

Almost DIN but not quite... About 1.5 DIN. Front face is not part of the panel, at least, but the unit is attached at the front so the mounting kit needs to have that adapter else nowhere to attach it to the vehicle.

[redwire]

Re: Car radio stopped working

Does it have an active antenna? I have seen these get water in them and then croak.

[RJARRRPCGP]

Re: Car radio stopped working

AM works, FM does not work. Tuner problem. Has COB's. Probably lost cause.

I don't think I saw the term COB before when used with a radio. What's that?

I can think of COF, for chip-on-film, which can be miserable!

[eccerr0r]

Re: Car radio stopped working

Same as the usual definition - chip on board, one of the daughterboards has two dies (dice?) black epoxied onto the board itself...

... if someone thinks of sanding off tops of ICs, try identifying ICs that are epoxied on the board!

Active antenna? Don't know, don't think I have an RF preamp. The troubleshooting guide in the service manual says "exchange radio" ...

[stj]

Re: Car radio stopped working

so does it have a real antenna, or is it using the screen heater or a tiny fin?

[eccerr0r]

Re: Car radio stopped working

Real antenna. Not even a power antenna, just a real antenna.
I don't think I'd be getting AM stations if the antenna was borked, so I have to rule out the antenna...

[petehall347]

Re: Car radio stopped working

you might get AM ok even with marginal antenna .. i have been in plenty of cars that only get AM because of it . FM likes a ground connection . well thats what i find .

[redwire]

Re: Car radio stopped working

Active antenna pre-amps can get water in or a bad connection on power, and almost a total loss of FM signal. AM makes it through anything.
Or the coax can get water in it, try ohmmeter it.
In the shop we just poked a jumper on the antenna jack to see what happens.
People put in aftermarket radios and the antenna stops working mysteriously. They forget to keep power to the antenna or bias-tee, which the stock radio provided.

In car radios, I find it's almost always broken solder joints. Tapping the pc boards to flush that out. Unless lightning/static zapped the front-end hard, but there's usually a gas-tube there.

[eccerr0r]

Re: Car radio stopped working

Most curious. Tuned to a known FM station I poked the antenna wire with a metal wire and... well... still dead.

... however I hear popping...

HMM...

[eccerr0r]

Re: Car radio stopped working

Well, today's debug session was kind of annoying.

I had broken the power output lead in my bench PSU, and was wondering why my radio didn't work at all on my bench. Finally tried shorting the output cable expecting the current to go up... it didn't. Alligator clip wire was found to be broken.

So I needed to resolder. My 100W solder gun is now taking forever to heat up... well, guess what, I need a new tip for it. Grr. Well, I just let it heat up however slowly it does and finally was able to resolder the alligator clip to the wire.

Now my radio powers up on the bench. With the pinout in hand I probed the pins... Glad I have a 300MHz scope (or too lazy to get the frequency counter set up) and confirmed the local oscillator is dead or at least it doesn't trigger the rest of the PLL circuit to work properly. Since the LO is on the COB TEMIC module, debug stops here, need to locate another TEMIC module to repair the radio.

[eccerr0r]

Re: Car radio stopped working

COB Hell.

Yes there's more components on the other side, though covered by the shield.

[stj]

Re: Car radio stopped working

pull the shield.
just from that picture i think it may recover just with a good fluxing and a re-heat of each joint.
though from experience with sattelite tuners i would test the semiconductors - they are probably on the edge of there rating