Sony CFM-D1 doesn't work.

[panchoskywalker]

Hello, I have this sony radio that keep bringing me problems. I've opened it and cleaned a few times but the radio still fail.

What can I do?

PS: Cassette is playing on this video but the problem is with the radio, cassette works fine. The problem is the radio keep losing signal and most of the times it just doesn't catch anything. Opening the antenna doesn't change anything.

 

[MaxwellsEq]

If opening the antenna does nothing, there may be a faulty connection between it and the main circuit board.

 

[AnalogSteph]

Is the problem affected by wiggling the function switch (tape / radio) or the bandswitch?

I would want to measure what's going on at pin 28 of IC101 and whether the 4.1 V voltage out of Q105 is nice and stable.

There is not too much that could go wrong in the audio path itself, although it might still be that C18 has leaked and corroded off one of its legs, or there's a hairline crack in the board or a bad solder joint on one of the ICs.

Arm yourself with the service manual and study it if you haven't already.

 

[panchoskywalker]

If opening the antenna does nothing, there may be a faulty connection between it and the main circuit board.

Sometimes it helps but sometimes it doesn't, most the time the signal comes ans goes.

 

[panchoskywalker]

Is the problem affected by wiggling the function switch (tape / radio) or the bandswitch?

I would want to measure what's going on at pin 28 of IC101 and whether the 4.1 V voltage out of Q105 is nice and stable.
View attachment 315144
There is not too much that could go wrong in the audio path itself, although it might still be that C18 has leaked and corroded off one of its legs, or there's a hairline crack in the board or a bad solder joint on one of the ICs.

Arm yourself with the service manual and study it if you haven't already.

Wiggling the volume and the bandwidth function (FM/SW1/SW) affects the problem but most of the times signal comes and goes even if I don't touch it.

 

[panchoskywalker]

The problem seems to be the antenna because when I removed it, it works much better. The origin of the problem is that the feet where the antenna is supposed to be screwed in is broken so I have to rebuild it with poxipol but there's a spring I don't understand how it goes.

I've found a vide on YT that shows the spring but it seem to be flat while the one I have is not.

Does this spring has any important function?

 

[AnalogSteph]

The green arrow is pointing at the wrong spot - the antenna connection is the hole there on the right-hand side, right underneath the screw head. You can still see the imprint of the spring in the solder.

The spring in the YT video is not flat either, there is clearly a kink in it in the 3rd dimension. It needs to go between the two holes as seen in the video, with the 3D part going into the case back. There's one larger and one smaller post, which should be reflected in the spring as well, so there's only so many options.

I think the case back is bowing out slightly, so the antenna fixing screw is not parallel to PCB mounting screws, and they had to make up for that.

The spring itself is merely a contact spring... you could basically use a piece of wire instead but it would suck for disassembly.

 

[panchoskywalker]

You're right about the antenna connection, it's the hole, I realized after posting the picture. The spring makes the connection between the antenna and the pcb. At the end I managed to fix the spring on the case back with poxipol and rebuild the antenna screw as well.

It seems to works fine but I'll probably have to do it again as it will probably brake because of the strength I apply when I move the antenna one side and the other.

 

[zam11]

can you send the picture of the antenna for this model like how it connects to the spring. I have the same radio but have lost the whole antenna

 

[zam11]

tried using different wires instead of the antenna it's working but the the volume output is too low even using external speakers using the 3.5mm audio jack. Either its something wrong with the amplifier or the audio jack has gone bad causing hindrance?? Can someone help Plz

 

[AnalogSteph]

but the the volume output is too low even using external speakers using the 3.5mm audio jack.

Just to confirm, these are external active speakers, right? That's a BTL mono output with one half of the amplifier driving the ground side via a 82 ohm resistor and the other half the left channel, so even an 8 ohm speaker would see considerable attenuation.

If it's not the normally closed switch in the earphone socket that's causing you trouble and needs some contact cleaner (or the tape/radio switch), you will have to get measuring. Minimum with a multimeter, ideally with some kind of signal tracer (basically some sort of small active speaker with a coupling capacitor in the input to keep any kind of DC off). Make sure the buffer circuit and the amp IC get their supply voltages and check for any abnormalities. Keep an eye out for any mechanical damage (cracked PCBs) as well.

This unit is also over 25 years old now, so finding some dead electrolytic caps is not out of the question. You can try bridging suspect ones in the signal path with a small spare one.

Do you hear a normal level of scratchiness in the volume pot? If not, that would narrow down the area.

Seems like you got somebody else's defective parts donor.