Step 13: Troubleshooting and enjoyment
My radio doesn't quite work right!
It hums! If you replaced the filter caps, there's a chance you have a weak rectifier tube or a bad audio amp tube.
It's deaf! Make sure your antenna is ok and wired properly. Try turning the radio. The antenna is directional. If that doesn't solve it you may have a weak tube.
It doesn't play very loud before it sounds fuzzy. You may have a weak audio amp tube. Peek inside the cabinet while the radio is on (remember not to touch any metal so you dont get shocked!) If you have a tube that has a deep violet or deep blue glow inside the glass while it's powered up it may be a worn audio amp tube. Note the position of the tube on the chassis, UNPLUG the radio, get the tube out and look up it's number on the web. If the tube comes up as being an audio amp tube it probably needs replacing . A common audio amp tube on AA5 radios is the 50L6 and the 35L6. They are cheap and easy to get from tube vendors.
I get a raspy buzzing noise between stations. Electric eye lamps (lamps that turn off during the day automatically) have been known to create nasty noise on AM. Check on a known good AM radio to see if you get the same noise. If you do, your culprit is not the radio itself.
Radio sounds good at first then begins to sound distorted as time passes. You may have an out of spec resistor. While the radio is on, peek inside the cabinet being careful not to touch any metal so you don't get shocked. Look for a tube who's metal structure inside is glowing orange or red like its gonna melt. I'm not referring to the heater filaments as those are supposed to glow orange. If the tube structure itself is glowing from heat you may have a bias problem which is more than likely in the audio amp circuit of the radio. Obviously you can't perform this visual check on all metal tubes. Either way, it's time to get out the schematic and meter.
Following these same instructions I have resuscitated several old tube radios. The AA5 was built for simplicity thus there isn't much to go wrong and they are forgiving. Once your radio is up and running, enjoy it. Use it every so often. Just like an antique car, its bad to have it sit unused. Fire it up every now and then and show off your work!
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