How to diagnose an old receiver?

[EvilYoda]

So I picked up a Scott 320R today for $20 - he said it wasn't working but I figured it was worth a shot. If nothing else, I liked the knobs and chassis for other applications. That said, I brought it up and sure enough, no sound.

The unit lights up when turned on, the fuses look to be intact. Nothing from speakers A or B or headphone. There are switches for Speakers A and Speakers B - when I turn them off while the unit is running, I hear a sound from the speakers so it seems like there's still a signal getting to them. Nothing from FM, AM, or the aux input.

I pulled the top off to see if there was anything obvious but I can't find anything. Not that I really know what to look for, I've never done this sort of thing.

Any suggestions on what to try? I've never tried diagnosing something like this. Thanks.

[Tekko]

Could be oxides in the switches and in the dc protection relays if there are any.

Get ahold of a schematic.

[firechief]

When you tune around in AM or FM do the needles move at all? It may be nessisary to hook a short piece of wire to the antenna terminals, but you should get some indication that the radio section is still alive. Also pictures of the inside would help. The manual is readaly avaiable for free on the web, so If you really want to get into it, you could download it and post just the schematic here. Next step after that involves a voltmeter, so try to get hold of one. Also, with the unit on stick your ear right next to the speaker to listen for hiss. Report back.

[kevinahcc20]

Keep in mind if this is your 1st outing that when plugged in there will be line voltage present in the power entry, fusing, and power transformer and potentially high DC voltages in the power supply (even when unplugged). You should consult the information on this site regarding safe work practices before proceeding.

[DF96]

Unless you are an expert on old radios you won't get far without a service sheet. Even the experts prefer to work from one, if available. A quick Google suggests that a sheet is available for this radio.

[sregor]

service manual available at elektrotanya SCOTT 320R 320RL 330R 330RL SCH Service Manual free download, schematics, eeprom, repair info for electronics wait for the Get Manual link to appear to the right of the picture of the manual - avoid the ad links.
Check for obvious tape monitor switches, shorting jacks in tape out. Clean and work switches and controls - volume and selector. Next step would be to check power supply voltages. How far you want to take it depends on your tech savvy and confidence. Good luck.