anybody own am tube radio

When I was a kid, I used to listen to my grandfather's AM tube radio. It was a breadbox sized Philco, I believe vintage 1940s. It had excellent reception and excellent sound due to a big old 6x9 inch speaker on the bottom. I would like to get me a am tube radio. I see lots on ebay in various conditions, a lot pretty cheap. But I know nothing about them, what is good and what is not. Where can I learn more?

I used to listen to a Grundig that my dad got when he was stationed in Germany. It had a rich tone to it. This is why diehard audiophiles insist on tube amps.

As for which to buy, look in your local yellow pages, you may be surprised to find a dealer who sells vintage radios.
If you do find one go there, hang out and listen to what he mave have and bend his/her ear as to what you should look for. /ubbthreads/images/graemlins/tongue.gif

Most of the tone difference is related to how a Vacuum tube Audio amplifiers handle overload. Basically you can beat them to a bloody pulp, and you are unlikely to damage them, and unlike solid state amps, it really doesn't mess up the sound quality very much. Most vacuum tube amps that were rated for say 20 watts RMS output could in fact delivery 200 watts peak without either damaging themselves, or producing the really gross distortion you'd get from most transistor amps.
Unless you run a transistor amplifier in class A operation, some level of distortion is unavoidable because of the inherent non-linear characteristics between 0 and .6 volts.
(If you run class A, you never get down that low, the device is always 'on'). Technical and economic considerations preclude the making of 100 watt class A amplifiers for anyone who cannot afford his own biz jet!

If you want sound quality, generally you are going to want a tube radio with push-pull output, and nothing smaller than a pair of 6V6's running class B (that will give you about 15 watts), 6L6GC's will give you about 30 watts. After that you start looking at big power tubes like 811's.
IN any case look for a power transformer, and a pair of identical tubes next to a second transformer (audio output transformer).

If you find a 50C5 and a 35W4, you are looking at a classic 'All America 5', serviceable yes, Hi-Fi, forget it. The main claim to fame with the All America Five was that it didn't need a power transformer (which made it cheap to build). Most 4 and 5 tube radios are All America Fives, or a variation. (The Variation is often the 35W4 rectifier is replaced by a solid state rectifier, and the 35V drop is provided by a combination of dial lights and/or Glo-bar droppiing resistor. For example the Heath Kit Low end shortwave radios like the GR91 are exactly this variation of the All America Five design and added an Isolation transformer for safety. The bad news is the sloppy hobbyist who worked on an All America Five was likely to get a shocking surprise, if he wasn't electrocuted! Generally one side of the chassis was connected to the line cord, so if you were lucky, it was connected to the neutral, if you weren't, well... (and these are much older than polarized plugs!)..

Purists will insist on class A, but class A has a maximum theoretical efficiency of 25% (and the desire for ulta linearity and practical consideration generally limit it to 20% or so, so for any reasonable power output, you are actually buying an electric heater for the room.

If you over drive a vacuum tube amp , they become non-linear, but unlike solid state amps, they won't 'flat top' which produces horrendous distortion products, and or blows the fuses to protect the transistors. Most transistors won't tolerate even short term gross overloads. By contrast, there are vacuum tubes that were actually designed to take short term overloads of 100000% (yes a 1000x overload, such as an Eimac 4PR1000A). Most garden variety tubes will tolerate 1000% overloads for a fraction of a second without any damage at all.

Ones you buy used at this point usually need some work. The electroyltics in the power supply have generally had it, and many of the other caps are suspect. These are analog devices, and drift with time, so it is usally necessary to re-align the front end and IF strip. On an AM radio you can generally do it by ear. On an FM radio, you are going to need an oscilloscope and a sweep generator. Most are in fact 'stagger' tuned to provide the required bandwidth for FM.

I've got my Grandparents old Crosley 66TA AM/Shortwave like this one. It still works, hums pretty good - I'd like to find some tubes & caps so I can replace them all. Maybe that would quiet the hum...

yep, got an old 50's AM/FM tube amp console w/record player

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geepondy said:
Where can I learn more?

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Type "antique radio" into Google and you will find a wealth of information. Also, there are a few books on antique radio currently in print - try Amazon.

Please be aware that these were manufactured without much regard for safety. As stated above, many have the opportunity for hot chassis, especially if the manufacturer saved money/space by omitting an isolation transformer. Further, the old caps may not only be weak, they may fail via internal short circuit and burn. So don't leave an un-restored radio plugged in. I have even heard of 1930's radios that had heir "dropping resistor" in the line cord, all of which are probably unsafe by now if they ever were safe.

Even if the radio doesn't have any major problems, persons unfamiliar with this equipment should stay out of the inards since they use high voltage which can be present even after the line cord is disconnected.

I would suggest getting a professionally restored radio, preferrably one with a transformer, a new polarized line plug, and replaced capacitors.

I'm basing my warnings on what I've learned in the last six months. I found a 1951 Zenith Transoceanic and I have been working on restoring it. When I first found it, I plugged it right in the wall and started to fiddle with the tubes to see if reseating them would start it up. Little did I know that this action probably blew one or more of the tubes because of the idiosyncrasies of this particular circuitry. Furthermore, I mistakenly assumed that the chassis was neutral - and it's damned fortunate I didn't get a nasty shock for my ingnorance. It was as dumb as grabbing hold of the black wire in the wall! Anyway, God protects drunks and fools so I lived to do the proper research on how to service these radios relatively safely. This includes use of an outboard isolation transformer, a Variac to reform caps, replacement of electrolytic and paper caps, safety caps across the line and line to ground, etc. It's a whole new world and a lot of fun but it is pretty dangerous without a fair bit of knowledge under one's belt.

Typical Tube circuits produce harmonic distortion in the even harmonics, which creates a warm sound.

Typical Bipolar transistor circuits produce odd harmonic distortion which is edgy sounding, like brass, as it squares up the waveforms.

MOSFETs can be used in a fashion to produce even harmonics for warm sounding distortion like tubes.


BTW, you can also build your own tube radio, from scratch or using one of the many kits available. Here is one place to poke around:

http://www.crystalradio.net/#tuberadiosection

i have approx 50
everything from a crosly pup to a scott 800.
and thats not counting tv sets and tubes.
here is imho the best site for vintage electronics.
http://antiqueradios.com/cgi-bin/forums/index.cgi
and the same for vintage stereo gear.
http://65.219.61.150/forums/

I have a GE plastic case tabletop model that was likely produced in the late 1940's. The tuning dial glass is damaged, but in good condition otherwise. The sound really is a combination of a larger speaker than common portable radios and the distortion created by the tubes. For some reason the distortion from tubes makes the sound kind of mellow. The story of acquiring it is kind of different.

Around 14 years ago my mother's aunt was selling her country homestead to move into the city. I found a couple of old tabletop radios in the stuff being gathered together for customary the rummage sale she was having prior to moving. I took them with the intent of restoring them, but the terrible condition of the radios just stopped me from doing the work. A couple of years later, my employer's father had died and my employer was involved with cleaning up the estate. The father had owned a radio repair shop for years and had a stockpile of mil-surplus tubes, many older glass tubes, service manuals and test equipment. I discovered the a batch of this stuff in our dumpster at work and promptly rescued it. I found out that a lot of other items had already been tossed out, but the remaining equipment would be saved for me. Among the equipment was a portable tube-tester that needed all the paper capacitors replaced. A year or so later, my next-door neighbor had cleaned his garage and set up a very small rummage sale with the stuff he didn't want. I bought the GE radio I use now from him for 50 cents. I checked each tube with my tester, found 4 out of 5 were weak, and had multiple replacements on hand to repair. I cleaned and polished the case, and the radio gets regular use listening to talk radio and football games to this day.

The 2 old radios from my great-aunt's estate are still in pieces in a box. Even the wires are rotted in them - major rehab needed.

I probably should point out that the high end tube receivers, like the Drake's, Collins, National's and Hammerlund cannot be materially improved on technically. (most of the Hallicrafters receivers weren't nearly as good). National and Hammerlund are history, but Drake is still alive in Miamisburg Ohio (The Grundig Satellite 800 is actually a Drake Design), and Collins is Rockwell Collins these days, and very active in the Avionics and inflight entertainment business.

The latest can be made a lot smaller and lighter, but by the early 1950's the performance was already limited by atmospheric noise, not electronics! Even by today's standards the shape factors in the IF strip of these receivers are excellent.
The result is 40+ Year old Collins A , S and military receivers command prices that are probably higher than they were when they were new! Once these things are cleaned up, re-aligned, and caps replaced, they are literally goods as new. The best deals out there are probably in the Drake 2 series (2A,2B and 2C), but if you want an attention getter, find yourself a Drake 1A.

Once upon a time WA3CEM....

What a great discussion on the ol' fire bottles. I've had a couple of those "All American 5" radios and I remember those weird filament voltage ratings that had to add up to 115v. And of course the filaments were in series to achieve this, so if one tube lost it's filament the whole string went out. Then it was time to pull out the VOM (remember VTVMs?) to find out which one was the culprit.

I also remember getting many shocks from the chassis. A hot-chassis radio has one leg of the AC power tied directly to chassis ground, and back in the days before polarized outlets and plugs were popular, it was really easy to plug it in the wrong way and have a chassis that was at 115v!

I've always been impressed by the way a tube can handle an overload better than a P-N junction. I remember breadboarding an AM-band oscillator with something like a 6V6, and I decided to see how much power I could crank out of it. I was able to run that tube's plate current up to the point where the plate was glowing red hot, and it still worked! /ubbthreads/images/graemlins/cool.gif I probably wiped out AM radio reception for a half-mile with that little experiment.

My Aunt and Uncle owned a "Radio and TV" store in a small town (Huntington, Indiana, "Huntington Radio & TV") and I remember visiting the "store" often in the late 50's and early 60's.

I restored a beautiful, floor standing radio that I still have, along with a Philco "table model" that my aunt left me.

At one time I collected and restored older "tube types", but my wife didn't like, the amount of room that they seemed to fill!!

Still have an old "wooden cased" tube tester!

jeffb

Hey, thanks you guys for the heads up on electrocuting myself! I have my parents 1950s era first new radio they ever bought in storage, and been meaning to haul it out and try to restore it. It looks great, but doesn't work so good. I'll look youse up when I do!

daloosh

daloosh - "The Human Torch"! /ubbthreads/images/graemlins/grin.gif (Hopefuly NOT!!)

tube radios sound more better in my opion

ZZZZTTTT!!!!!! SPSPSCCCSAZZTTTSSKTTT!!!!!
mmm. electrocutin' bad.

I always loved the Fantastic Four as a kid, but the bad reviews this new movie has got has scared me offa spending my hard earned cash to see it. Also, my wife refuses to come with me. Well, at least that's one less ticket I have to buy! LOL!

daloosh

Tube radios have a nicer, warmer sound.

They also have AC hum, require high voltage DC, chew up lots of AC power, and can heat a small room in the winter!

OT - but, I heard Batman was good?!

My grandparents used to have a Telefunken radio. I have no idea what happened to it.

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greenLED said:
My grandparents used to have a Telefunken radio. I have no idea what happened to it.

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Sounds like a song from "Parliment" (you know the folks who did "Maggot Brain"!)

Do you think "Telefunken" is German?