How to troubleshoot an FM radio.

[neo]

I have a Sony 7f-74DL 11 transistor radio, my favorite fm radio. It worked last year but it was misplaced and lost over the winter, i find it again and try to turn it on and nothing. No sound at all, though the light does work.
Where should i start? I checked the battery voltage and it is exactly what it should be.
4.52 on, 4.60 off, 4.40 with lamp all within tolerance of 4.5 volts.

[RoGeorge]

No sound at all, not even when turning the radio on or off?

Maybe the speaker went open circuit, or some contact for the external speaker connector get oxidized (if it has such a connector), maybe just a broken wire.

[neo]

I clipped my oscilloscope to the speaker and did get some noise on it when turning the lamp on and off, though that is all i get on it.

[IanMacdonald]

Radio faultfinding: Check the obvious like PSU lines and the like, but then proceed to a logical half-split faultfinding technique.

The speaker switch on the headphone socket is a favourite for going o/c especially after storage. Try headphones. If they work, that's your problem. Clean the contacts with WD-40 and working the plug in/out. (avoiding getting it elsewhere, of course)

What you then really need is a signal generator. Try injecting 400Hz into the audio stages. The volume control, if analog, is a suitable injection point. If that works, try injecting IF, and then RF. That way, you can identify which stages the problem is in. Much faster than random poking with a voltmeter.

Note that when injecting signals you need a small capacitor (say 10nF) in series with the sig gen hot lead. Otherwise the sig gen creates a path to ground, altering bias.

If you don't have a sig gen you can 'scope for audio at the detector and possibly for the presence of 10.7MHz IF,  but to check the RF stages that way you'd need a fairly high performance 'scope. Injecting and listening generally works better than measuring, especially as measuring signals depends on the radio being tuned to a station, which is kinda hard to confirm if it's silent!

[Cyberdragon]

Here's a manual for a similar model: https://elektrotanya.com/sony_7f-74w_sm.pdf/download.html Can't get the exact one due to needing accounts or having to pay for it (which is total ).

EDIT: apparently that is just the schematic, but that's all you really need. There is also a voltage check chart.