Magnavox 480P AM/FM tube radio

[mjennens]

I picked up a nice looking Magnavox 480P radio that has at least one problem. The AM works very well, but the FM makes no sound at all. I'm a newbie to these things, but it's really nice and I'd like to see it turned into a fully funtional AM/FM mono radio. Any ideas where I might start to look to get the FM to work?

It's a model 480P. It also had a turntable/record player that I don't really want to do anything with.

http:s287.photobucket.com/albums/ll1...%20Info%20Tags

http://s287.photobucket.com/albums/l...Compressed.jpg

[Jeffhs]

Originally Posted by mjennens

I picked up a nice looking Magnavox 480P radio that has at least one problem. The AM works very well, but the FM makes no sound at all. I'm a newbie to these things, but it's really nice and I'd like to see it turned into a fully funtional AM/FM mono radio. Any ideas where I might start to look to get the FM to work?

It's a model 480P. It also had a turntable/record player that I don't really want to do anything with.

http:s287.photobucket.com/albums/ll1...%20Info%20Tags

http://s287.photobucket.com/albums/l...Compressed.jpg

I had a Magnavox radio exactly like yours years ago, a thrift-store find. Chassis only, no cabinet or speaker. Had to rewire the speaker socket, as this particular radio apparently used a field-coil speaker rather than a PM (permanent magnet) one. It was well worth it. I used the radio for some time in the basement of my former home in suburban Cleveland using an old cheap car-stereo speaker but it worked very well, getting every major FM station in Cleveland, just using a 6-foot length of wire on the FM antenna terminal.

Yours should work just as well on both bands. Be sure you have some kind of antenna on the FM antenna terminal strip on the rear apron of the chassis, even if it's just a length of wire; if you try to pick up anything on FM with this receiver without an antenna, it just won't work unless you are within spitting distance of the stations, and even then I wouldn't count on hearing too much. As I said, you don't need much of an antenna in most areas; even a pair of rabbit ears will work in near-suburban environments. I don't know how many local FM stations you have in Bismarck, but you should hear at least one or two if the radio is working at all.

If your set still won't work on FM even with an antenna, I'd test the tubes in the signal circuits and replace any weak ones. The tubes in the radio are probably 60 years old or more (many of these oldies still have their original tubes), and the radio itself likely dates back to 1947 or 1948, especially if there is a position on the function switch marked "TV" as yours has. This would indicate that the chassis is very likely from an early three-way entertainment center, with AM/FM radio, phonograph and a television receiver.

Clean the controls while you're at it, especially the function switch. Your loss of FM signal could be due to something as simple as a dirty contact on that switch; if you can make the signal cut in and out by wiggling the switch around, it's either dirty or worn out.

I would also replace the capacitors. In a radio of this vintage, many of the caps are either bad or going bad, particularly in the power supply. The three-section electrolytic in the power supply of this receiver, indeed in all radios 60+ years old, is probably on its last legs if it hasn't failed already; replace it with a fresh one as soon as possible. A defective capacitor could be the cause of your FM problems as well; check the caps in and around the tuner under the chassis, but be sure you have a schematic diagram first. In a radio of this vintage, again, there are probably dozens of capacitors that should have been replaced by now.

IIRC, your Magnavox radio has a small tube on the chassis that looks like a full-size metal tube which was squashed by a steamroller. This will be a 6H6, again IIRC (I'm going by what I remember my own Magnavox chassis looking like) which was used in this chassis as an FM discriminator; if it gets weak or goes bad altogether, you can lose the reception on the entire FM band, although the AM will continue to work as if nothing has happened. I don't recall offhand if there are any modern substitutes for this tube, although you can check with Antique Electronic Supply, as they have rare, hard-to-find tubes and parts for all types of antique and vintage radios.

Good luck. Once you get that radio working, you should have a fine example of early high fidelity that will continue to play for years. These old sets were built like tanks, so if you get it going, you will have a receiver that will run rings around today's plastic headphone stereos, boom boxes and the like. This particular Magnavox should sound very good as well, even with a so-so speaker, as it has a push-pull audio output stage. You won't be disappointed with the sound. These older radios and combination units, not to mention those fabulous 3-way color console TV units with AM/FM/stereo FM and phonograph (especially Magnavox's Astro-Sonic stereo theater with 25" TV and Total Remote Control from the mid-1960s, which controlled everything on the set by means of a small hand unit and had a system of cams, gears, motors, belts . . . to control it all that was, or could have been, a serviceman's worst nightmare) set a standard for outstanding sound quality that most of today's offshore-built stereo systems and portable full-size boom boxes would be hard-pressed to equal, let alone surpass. Magnavox (the original Magnavox Company of Fort Wayne, Indiana) was a leader in the high-fidelity field for many years second only, IMHO, to Zenith, when the latter was building its own TVs and stereo consoles, etc. in Chicago. When these companies were taken over by offshore interests some years ago, we saw the end of an era the likes of which we will, unfortunately, never see again.

[mjennens]

Thanks Jeff,
Can you give me any info on testing the tubes? I remember going to a local "Western Auto" store with my dad to test the tubes from our TV when I was a kid, but that was long ago... Anyway.....
I have the speaker that came with the radio. It's quite the speaker, and it does appear to be a field coil speaker. I've also been told so on another posting. It all came in the cabinet, but the cabinet was in very bad shape. If I can get this thing working, I'd like to build a new cabinet for it. I'd also like to figure out how to wire an RCA jack to work with the jack for the TV. Any ideas on that?
Not a lot of FM stations in Bismarck, probably about 12, some stronger than others. I'm a Cleveland (Eastlake) native myself. Go Browns!!!

[Jeffhs]

Originally Posted by mjennens

Thanks Jeff,
Can you give me any info on testing the tubes? I remember going to a local "Western Auto" store with my dad to test the tubes from our TV when I was a kid, but that was long ago... Anyway.....
I have the speaker that came with the radio. It's quite the speaker, and it does appear to be a field coil speaker. I've also been told so on another posting. It all came in the cabinet, but the cabinet was in very bad shape. If I can get this thing working, I'd like to build a new cabinet for it. I'd also like to figure out how to wire an RCA jack to work with the jack for the TV. Any ideas on that?
Not a lot of FM stations in Bismarck, probably about 12, some stronger than others. I'm a Cleveland (Eastlake) native myself. Go Browns!!!

Hmmm. I don't know what to tell you as far as tube testing goes, as the drugstore tube tester disappeared decades ago; with everything being solid state these days, the need for tube testers is nowhere near as pressing as it once was, although there are a few circuits that still rely on tubes (mainly high-power amateur radio and broadcast power amplifiers). I've been experimenting with electronics for 40+ years and am an amateur radio operator, but it has literally been years since I saw a tube tester. The last one I remember is an old (1950s or perhaps earlier vintage) Eico 625-04 tester my dad had. This tester probably dates before the '50s as it had, IIRC, a type 80 rectifier tube in its power supply.

I looked up Bismarck's FM stations on RadioStationWorld (www.radiostationworld.com) and found only about twelve FM stations, as you stated. Since the city is in North Dakota, though, I would imagine you can get stations from Montana and even Canada on a good day. Here where I live in northeast Ohio, a mile or so from the south shore of Lake Erie, I can hear all Cleveland stations, Detroit, Michigan and Windsor, Ontario stations, as well as several from Leamington and Chatham, Ontario; in fact, earlier this morning I was listening on my Zenith MJ1035 to CIDR-FM 93.9 "The River" in Windsor, Ontario, which also serves the Detroit area. This station was known as CKLW-FM until perhaps a year or so ago.

I lived in suburban Cleveland for 43 years before moving to Fairport Harbor in November 1999. The details of why I moved are off-topic for this thread, but I will say that the main reason I moved here is that I always wanted to live in a small town (our population here is 3,220 as of 2006) after having grown up in the suburbs (I also lived in an inner-ring Cleveland suburb called Cleveland Heights from 1972 until 1975). After finding out I had to move in late 1999, again skipping the details, I moved to my current location in November of that year, and have been here ever since.

The radio reception here on AM and FM is excellent, but the television reception leaves an awful lot to be desired. I can get decent reception with an antenna on only four UHF stations (the ABC, CBS and FOX stations in Cleveland, all VHF, are fair to poor at best with rabbit ears), and the Cleveland NBC affiliate on channel 3 doesn't reach here at all; for these reasons, most folks here either have Time-Warner cable service or DirecTV or Dish Network satellite. I guess it must be the terrain features of this area or something between here and Parma, Ohio (a southwestern suburb of Cleveland), where all of the Cleveland TV transmitters, analog and digital (seven analog channels, 3-5-8-19-25-43-61) are located, that makes TV reception on antennas so bad. Another crazy thing that happened in Cleveland regarding the city's CBS television affiliate was when that affiliation was moved from its longtime home on channel 8 (42 years) to a UHF station (channel 19), the latter channel being where Cleveland's CBS has been since the early '90s. (The station didn't even have a local newscast until it had been with CBS about five years.) The details of that switch are a story in themselves (and off-topic, again, for this thread), so I won't go into them here. However, I am wondering how the TV stations in North Dakota are doing as far as the digital transition next year is concerned. Your state is wide open, probably with a lot of land separating homes from one another, so analog TV reception there could be a problem. I don't know how digital will work out there, unless you have cable or satellite service available. My best guess is you do, as there probably aren't that many local TV stations in the Bismarck area.

Nice to meet someone originally from northeast Ohio on AK. There are many folks here who live in the area, such as dr*audio, fsjonsey, myself, et al. so this area is well represented here.

[radiotvnut]

If you can find a basic emission type tube tester, such as an Allied (Knight) or Heathkit, it should serve your purpose. You might try the older TV shops in your area. They might just have something you could buy real cheap. Also, I've seen tube testers at ham fest and antique radio swap meets. There's always epay, but, the prices on there have gotten way out of hand. There's no way I'd pay in excess of $100 for a basic tube tester. The first one I had was a Knight 600A and I think I gave $20 for it in perfect condition.

[sampson159]

i just picked up the same unit with an fm problem too! mine came from a convent out of philadelphia. has a turtable that works and a reilly nice cabinet,however,owner said fm didnt work.haven t got into it yet. i will keep you posted!!

[Chad Hauris]

I think I'd go for new caps first and then some voltage testing before suspecting tubes necessarily...sometimes an electrolytic can have just enough leakage to cause an abnormally high current draw and cut off power to a certain stage yet not get hot or cause hum.

[sprman55]

Hi ok first do you resistance checks then check all tubes .See what you find doing that.Then recap it.after recaping check all voltages and dont forget to check all resistors to.Many times you will find a weak or bad tube and a resistor thats not reading right.Get the service info on it if you dont allready have it.Angelo

[sampson159]

my fm works!!! believe it or not,the knob was misaligned! previous owner said that it didnt work and he had it checked out at some repair shop.well,it works and i cant be happier. turntable was out of time. it works well now.this turned out good for me.strange how this unit came from a convent and exclusivley used by nuns,but all presets were rock and heavy rock.nuns just wanna have fun!

[sampson159]

here is my magnavox-all electronics work as they should and i havent got to the
small amount of work on the cabinet yet