If you have general questions about tube radio repair, please refer to Nostalgia Air.
Question from Jason (1951):
I would like to get the radio in my 51 to work, however I have check all the connections, and it is receiving power. But the radio does nothing. I would like to remove it, but I can't see how to remove the dash. Nothing is mentioned in the shop manuals anywhere. I know there has got to be a simple way, but I can't see it.
Reply from Arran:
It is ironic that you want to get the radio out of the dash of your car as I just removed mine yesterday. If your '51 is anything like my '54 the radio has two sections, the control unit and the amplifier unit. The amplifier unit is behind the speaker grille, and the control unit has the dial. These two are connected by a cable running from the control unit to a socket in the amp unit, find this and unplug it. At the back of the chassis for the amp there should be a brace held onto the bottom of the dash with a Phillips screw, remove it. If there is a cardboard cover over the amp chassis you will need to pry it off at the back of the chassis to get to the next part of removal. Feel around the back of the speaker where there should be two sets of 3/8'' nuts, the inner two hold the speaker on, the outer two hold the chassis to the back of the dash which need to be removed. You may need to remove the blower fan on the duct below in order to get the amplifier chassis out, this uses 1/2 inch nuts. Pull the chassis backward and down and it should come out. The control unit, or tuner, is easier to get out then the amplifier chassis. First pull the antenna lead out of its socket on the back of the chassis and disconnect the power wire. Undo the screw at the bottom of the dash that holds the radios brace on. Remove the control knobs from the front of the tuner. Next remove the 7/8 inch nuts behind the knobs and pull the chassis back and down. The radio probably doesn't work because the vibrator power supply isn't functioning.
I have the '52 Imperial in Indianapolis. The previous owner had taken the 14 amp fuse out of the power line to the radio. Yesterday I installed the correct fuse, turned on the radio and all it does is hum. I also noticed that when I checked the fuse after the radio was on, it was better that warm to the touch. Is this normal? Also, what is the next step to get something better than the hum?
The first question that I have to ask is how loud is the hum? Is the hum coming out of the speaker or from behind it? If it is coming from the speaker, and is loud, it probably needs new filter condensers? If it is coming from behind it, and has the sound of a fish tank pump, it may be the vibrator. The vibrator is a mechanical switching device that converts 6 volt dc to pulsating dc so it can be stepped up through a transformer. The vibrator is contained in a metal can plugged into a four pin tube socket on the amplifier chassis behind the speaker. The problem with them is that the contacts wear out from arcing and from the displacement of metal from one contact to the other, rather like electroplating, because the current is polarized. Fortunately there are solid state substitutes available that will plug right into the socket, a device that I have been trying to copy since I don't want to spend $20.00 American on one when it uses under $5.00 worth of parts. The first step would be to take the radio out of the dash and check that the tubes are in the right sockets according to the diagram pasted inside the box. Sometimes, in the case of my radio, the tube numbers are engraved in the chassis next to the tube or on the box just above the tube. The next step would be to have the tubes tested to see that they are in good condition, no weak or shorted tubes, etc. If the tubes are good then you must have either a wiring or component failure which requires a bit more work. But you're right its not normal for the fuse to get that hot and the only thing that would cause that is an excessive current draw. After you take the radio out and check the tubes over I'll give you some more ideas on how to fix it.
I don't know what year the Imperial first used the signal seeking type of radio, but they were available to the industry from 1951 (when Packard fired the Philco boys and started buying Delcos to get that feature). If the 52 Imperial has that feature, a reason for the hum and no other audio might be that the seeker is stuck in the "seek" condition and unable to find a station (for whatever reason). This would be consistent with the excess current drain. A 14 amp fuse suggests that it is a signal seeker type radio - does it have a "local-distant" switch or a "sensitivity" control? How about a foot button? ' But my money would be on a bad rectifier tube from the symptoms, assuming the signal seeker isn't present. Of course, there will be many bad electronics and probably the buffer capacitor is bad also, but the radio would work, however noisily, if that were the only problems. The rectifier tube will be the closest one to the vibrator: make sure it's filament is lit.
Question from Tim (1955):
Does anyone know what type of Buss fuse to use in the '55 Imperial radios? My question is I guess is would it be a special fuse as in 6-volt fuse vs 12-volt fuze or is there such a thing as a 6-volt buss fuse.
A fuse is a fuse. They are rated in amperes of current and are pretty much oblivious to 6 or 12 volts. My approach would to start at 10 amps and see if it will hold. If it blows try a 15 amp. That should be as high as you need to go.
Two things are key to this. One is that the fuse must be the correct strength. For the radio it probably is around 15 to 20 amps. The other thing is that in the '55 Imperial, the fuse is contained in a plastic in-line fuse holder. The holder is designed to take a certain physical size of fuse. It must fit in the holder, and the holder must be able to close correctly. There is a spring inside the holder that allows the ends of the fuse to make contact with the inside of the fuse holder. Usually, the fuse that fits the holder is the one that belongs in it.
It might be possible to fit an incorrect amp fuse in that holder so be careful. An incorrect amp fuse would either blow too easily because the "number" is too low (say a 10 amp fuse instead of a 15 amp fuse), or it wouldn't blow when it should, thus allowing damage to the radio or a possible overheating of the wiring if there was a short. In this case nothing will go wrong unless there is a short. Shorts can happen though, so you need the correct fuse.
My '55 Imperial is in storage, so I can't look at the manual at this moment to tell you what the fuse should be. I am thinking it is 15 amps. First find out the correct amps from the owner's manual or someone on the list, then buy a selection of fuses from your local auto parts and find one with that number that will fit the fuse holder. If the fuse holder is gone (some have been cut out of the line) you should find out the correct fuse, and then buy a fuse holder from the local auto parts store to install in the line. They are still available.
Question from Tim (1956):
Can anyone tell me why my Radio gets hot after about 30 min of running time. I just had it gone through and paid alot of money. I have it on the bench hooked up to a battery. Fuse lead to positive side of battery and grounded to negative side of battery. I know they get warm but when is to warm? I dont want to put in car until I know if this is normal.
A 1956 radio is supposed to get quite warm. Pre 60's car radios have about 8 tubes in them as this is before transistors were used. The tubes each have a heating element in them to heat the electrons. It is like having the heat from eight light bulbs trapped in a metal box. If it worked okay for 30 minutes and it is what I described here, it is working fine.
Tube radios get warm, on hot days they get kinda hot. You say your running it on the bench, is it flat on the bench? If you don't have it standing off the bench with air flow ALL the way around every side, it not going to get proper cooling and will heat up beyond normal. Normal is around 40F-80F above ambient air temp.
If you are looking for spare tubes, you are throwing you money away as car radios don't usually have enough hours on the clock to wear tubes out.
In the case of a vintage car you won't be using the car very much and the radio even less. In the case of the set in my car the tubes were all original and all tested like brand new. Nine times out of ten when you have a problem with a tube radio tubes are the last thing wrong with it.
Question from Jay (1962):
The radio in our '62 stopped working a few weeks ago, and I'm growing weary of self entertainment behind the rectangular wheel.
It's time to overhaul the radio. The tuning is gummed up from years of accumulated dust & dirt, causing the auto seeking function to only travel intermittently and in one direction. The speaker cone is cracked and it's got a bad rattle, and the dial indicator is faded and could use a swipe of fluorescent paint.
A few years ago someone had mentioned how to "clean" the internal mechanical workings, but I don't remember the solvent that was recommended. Whatever it was, brake cleaner, carburetor cleaner or electrical contact cleaner, it was to be sprayed on liberally and allowed to dry.
Does anybody know what I can use to clean my radio? (I do have a spare radio to test any theories)
I would assume that I would have to re-lubricate after such a cleaning.
Does anybody have any ideas that to help in cleaning/overhauling a '62 AM radio? Good sources for speaker re-coning?
Please be careful what you use to clean electronic parts. Even when it is designed to clean electronic parts some cleaners will eat the circuit boards, plastic parts, rubber, etc. I learned a long time ago to never use anything with any petroleum product, ingredient, or base. We have a radio station and are always cleaning equipment so we have a hell of a lot of experience. We eventually found a spray cleaner carried by radio shack that would not hurt plastic, rubber, or any other parts and it did not leave a film. It is called "Tronic Kleen". Once you have cleaned the parts you will need a lubricant for moving parts... that I cannot help you with
If you run out of cleaning ideas, I have two extra working radios, that I picked up a while back and finally got around to making sure they work. I'm asking $90.00 ea. plus shipping.
Question from Paul (1962):
Can anyone share any information on what may be the cause of a problem I am experiencing with the radio in my 62? The radio works. However the Loc/Dist buttons, as well as the floor button, when depressed, cause the radio to shut off. I have to turn it off via the volume knob, then on again to have it play. There seems to be something wrong with the scanning component.
Reply from John:
If the radio dial is moving when the loc-dist buttons are pressed, it is likely the antenna isn't raised high enough. If raised all the way & the dial moves, may be a bad tube. I had this with a 61 Chrysler, some of the tubes have 2 stages & the 2nd stage control the search tuner.
Tip from Arron on Imitation Tube Radios:
There are look alike radios but most are for Ford or Chebby. As far as I know there are none for Chryslers or Imperials. They aren't cheap either, the last ones that I saw advertised were going for $350 or more. They may have some for Plymouths or Dodges but I haven't run across any of those either. As for the late fifties Chrysler radios, to my knowledge, they did still have tubes in them at that point. As far as I know Imperials used tube radios up until 1963 or so but they may have been hybrid sets with a tube front end and a solid state audio output stage. They were excellent radios in their day and, once they are functioning properly, their selectivity and sensitivity is hard to beat with modern equipment. The only downside is that they are only mono but no car had stereo FM until the late sixties or so. By far the most practical way, if you don't want to bother restoring the old radio, is to get a modern unit, with remote control, and install it in the glove box. You may have to punch holes in the glove box liner to install it but that is a minor project compared to modernizing the original radio. The glove box is liner is only cardboard and replacements can be had for under twenty dollars, under ten if you make your own. Any stereo shop can supply you with a decent car stereo for under $300 and they come with a remote and CD player. Having the original radio gutted and modernized will cost between $400 and $600 and you don't even get a tape deck or CD player with it! My suggestion would be to repair the original tube radio and give it a chance. It may surprise many of you to learn that there are audiophiles out there who will search heaven and earth for the right tube amp and the right tubes. Guitarists are willing to pay thousands of dollars for a brand new tube amp over a solid state one. Why do they do this? Because the sound is so much different from run of the mill contemporary sound systems. If you don't want to deal with the tube radio right now that's fine, but don't destroy it for someone else down the road. It's very easy and cheap to replace a glove box liner, but it can be difficult to find another factory radio if you want to make the cat original. New factory pattern glove box liners are still being made, factory pattern tube radios are not. If you butcher a glove box you can easily get another. Once you gut an original radio and modernize it will never be original again. For me all this is just too high a price to pay for having the radio come on instantly rather then waiting for it to warm up.