AM works fine. Problem is that FM doesn't do antything. Radio does not have a visible FM antenna, but does have two screw connectors at back for an antenna. What kind of antenna might a FM radio have. I don't see the loop on power cord that Similar vintage Zeniths have. There is a wire goong from the speaker feild coil (a .20 type cap to isolate) to the antenna teminals. This was unhooked, but I suspect it went to the AM ground ant term and was used to ground the remote speaker. Could this be FM antenna related? I tried 300ohm coax and ribbon as FM antenna, but still totally dead, not even any pops or snaps. I suspect the FM coil is out, but would like to hook up reasonable antenna before I get into heavy de-bugging. Channel very quiet with only a slight 60 cycle buzz a max volume, so my guess is dead at fron end. Most of my radio book are older than FM, so I don't have much to go on for guidance. Help??
No rectifier is listed. Does your radio use selenium rectifiers? If selenium (Voltage drop goes up over time) replace with silicon diodes.
The only oscillator/mixer tube listed is 6BE6. This tube barly operates at FM frequencies. Try another 6BE6.
Call Sam's at 800-428-7267. Talking to someone sometimes is better than looking at an index.
Norm
:I have a magnavox 8 tube radio chairside that is i Suspect mid50's in vintage(6V6,12AX7, 6AL5, 6AV6, 6BA6, 6BA6, 6BE6, AND A 6BA6). Has broadcast and FM (80-108 MC) bands. There is no model on it, but the chassis says CR226.
:Can't find that chassis in Rider's or SAM's or at Antique Radio Supply. Any clues on where to go for Schematic?
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:AM works fine. Problem is that FM doesn't do antything. Radio does not have a visible FM antenna, but does have two screw connectors at back for an antenna. What kind of antenna might a FM radio have. I don't see the loop on power cord that Similar vintage Zeniths have. There is a wire goong from the speaker feild coil (a .20 type cap to isolate) to the antenna teminals. This was unhooked, but I suspect it went to the AM ground ant term and was used to ground the remote speaker. Could this be FM antenna related? I tried 300ohm coax and ribbon as FM antenna, but still totally dead, not even any pops or snaps. I suspect the FM coil is out, but would like to hook up reasonable antenna before I get into heavy de-bugging. Channel very quiet with only a slight 60 cycle buzz a max volume, so my guess is dead at fron end. Most of my radio book are older than FM, so I don't have much to go on for guidance. Help??
:AM works fine. Problem is that FM doesn't do antything. Radio does not have a visible FM antenna, but does have two screw connectors at back for an antenna. What kind of antenna might a FM radio have.
Fm antennas can be any kind of conductor -- closed loop, open short wires, anything. Line cord inductive coupling. Capacitor coupling. Doesn't much matter until you get a precise match to a proper balanced outdoor antenna feed. You will get SOME kind of FM signal, especially these days with so many FM transmitters around almost any sized community.
:There is a wire goong from the speaker feild coil (a .20 type cap to isolate) to the antenna teminals.
No, this radio cannot POSSIBLY have a field coil; not with miniature tubes! You mean, I suppose, the voice coil circuit.
:I tried 300ohm coax and ribbon as FM antenna, but still totally dead, not even any pops or snaps.
I am not sure if this radio has a ratio detector or a limiter-discriminator; I would probably assume the former. Therefore, you would not necessarily get a lot of interchannel pink noise. With a limiter-discriminator detector, between stations you'll get a monstrous amount of hash noise. If there is NO noise, and no audible station signals, then the FM section is simply dead. You shouldn't worry about an antenna; get the thing working and then optimize the reception. I am assuming here that you are not 300 miles from the nearest FM transmitter!
:I suspect the FM coil is out...
Why assume that? Why not assume that any one of the FM components is dead, starting with tubes that might be used (mostly) in the FM section?
:Channel very quiet with only a slight 60 cycle buzz a max volume, so my guess is dead at fron end.
Again, assumption is not called for. You could have a broken connection in the IF, or the local oscillator.
Usually all the tubes would work in both the FM and the AM circuitry, with the exception of the detector and POSSIBLY the FM oscillator. Change the tubes; if you have identical ones duplicated in different sockets, switch them around. Check the tubes. Use a scope to see if there is a signal at the output of the IF amp, going into the FM detector. Check back from the audio output of the FM detector to the front end, using a scope, to see where the signal goes dead. If you cannot do that, then find someone to help -- hams and electronics buffs everywhere will have a scope and many might be willing to help.
STEVE WALDEE
retired broadcast station chief engineer