Tube Time

Recently I completed restoring a Philco 48-225 AM tube radio. This radio was produced by Philco in 1948, and it was one of the first radio models to have a plastic (polystyrene) case instead of a bakelite case.

When I received the radio, the case was pretty scratched and banged up, and there was a big crack on the left side. Inside was a lot of dust and bits of dried leaves. Most of the tubes were missing, and the ones that came with it were the wrong type.

The case cleaned up nicely after a lot of wet sanding with fine-grit sandpaper and polishing with Novus 1, 2, and 3. The gold paint on the speaker grill was flaking off, but I decided to leave it alone. I saw a photo of the same model radio on eBay and someone had ruined the grill by trying to polish it–the gold paint is a very thin layer and it came off in patches.

Using superglue I fixed the crack and sanded it so that it’s barely visible. I hear you can also use a solvent-type glue, but I didn’t have any. The superglue repair is probably fragile so I will have to be gentle.

Turning the radio around, you can see the “All-American Five” tube complement. They are the 7A8 converter, the 14A7 IF amplifier, the 14B6 2nd detector/1st audio AVC, the 50L6GT audio output amplifier, and the 35Z5GT rectifier. All the tubes except for the 35Z5GT are of the Loctal variety. Unfortunately the back cover of the radio is missing.

Here is the underside of the chassis before I restored it. You can see how the paper capacitors are coming apart due to age. These radios were designed to be very low cost and were not supposed to last a very long time. The sectional electrolytic capacitor (the long pale tube on the upper right) in particular did not work at all because the electrolyte had seeped out completely.

I ended up replacing most of the capacitors. For this restoration I pushed the guts out of each capacitor and slipped the new capacitor inside the old one, sealing the ends with wax. This keeps the underside looking authentic.

Notice that there is no power transformer inside this radio. This radio operates directly off the AC line. The filaments for all 5 tubes are wired in series and the voltage ratings add up to the line voltage. The chassis itself is not grounded and it is actually part of the antenna circuit. There is a 150K resistor connecting it to one side of the AC line. The plug is not polarized so it’s quite easy to shock yourself on any exposed metal. It’s not a good idea to plug it straight into a wall socket because of this. If you try to add a 3 conductor line cord with the ground prong connected to the chassis, this will short out the radio’s antenna and the radio won’t work.

The solution is to use an isolation transformer. I have one connected to a Variac that I use to adjust the line voltage. When I first powered up the radio, I ramped the voltage up slowly to make sure there were no problems along the way. I also measured the line voltage and set it to 115V instead of 120V. AC line voltage was a little lower back in 1948. The difference doesn’t sound like much but running at the higher voltage would apply 6.6V to a tube filament rated at 6.3V. This is enough to reduce the life of the tube.

With the radio plugged in to the isolation transformer, the radio “floats” relative to the AC line, and it’s safer to touch exposed metal. It’s still a high voltage circuit so the one-hand rule applies. When the radio is isolated like this, it’s also safe to connect it to pieces of test equipment, such as an oscilloscope. The oscilloscope probe ground actually connects to the ground pin on the oscilloscope’s line cord, so if I had tried to test the radio when it was plugged straight in, I could have caused a short circuit that would have melted my scope probe.

It sounds pretty good now and it adds a vintage touch to the living room decor.

My Wagner fan restoration has progressed well (see previous posts). Recently I finished the final assembly. I took the entire fan apart and cleaned every part. Many of the parts needed to be repainted, and the fan blade needed to be stripped of the paint and polished.

Here are all the pieces laid out. Please click on the photo for detailed Flickr annotations. brittnybadger has taken some really great photos of household appliances in similar “poses.” I wish my photo was as good as one of hers.

The oscillator gearbox looks really interesting. Here it is before I added gearbox grease. It takes the high speed rotation of the fan motor and slows it down using two worm gears, and then drives the crank which rotates the fan from side to side.

There is still some work left to be done. The fan blade is made of steel which was copper plated before being painted. Time has not been kind to the plating. When I stripped the paint, I could see green corrosion and pitting that ruined the plating, so I had little choice but to polish off the rest of the copper plating. I have not yet decided whether to leave the blade steel or to get it copper plated again. Regardless of that I like the look of an unpainted blade.

The headwire which connects the fan motor to the base and the switch also needs to be replaced. The rubber insulation underneath the cloth has gotten brittle and cracked. Similarly, the line cord is not original and I need to do some more research to find out what an original line cord looks like.

Finally, I need to make some safety upgrades. I have already added a fuse in the base that will prevent shorts in the motor windings from causing a fire. I still need to add a grounding wire since the case is metal and could shock people if one of the motor windings touches it.

During the restoration process of my antique Wagner fan, I found that the bearings are a lot different than the Emerson 28646 I restored. This particular fan has a bearing on the front and one on the rear of the motor housing, and each bearing has an oil sump, some small holes to allow the oil leaking from the front and rear of the bearing to trickle down into the sump, and a wool wick that uses capillary action to “pump” oil out of the sump and bring it back up onto the bearing surface. Here’s a picture that shows how it all works:

In the picture, the oil sump is the lump protruding from the bottom of the round bearing housing. You can see the small hole that allows oil to drain back into the sump. On the inside of the bearing, there is an ovoid hole that lets the wool wick contact the rotating shaft and apply oil sucked up from the sump. You can click on the picture to see the Flickr annotations. Here is what the wool wick looks like:

The small round washer acts as a plug to keep the wool wick inside the bearing, and the hole is where you add oil. The wick itself is made of several strands of worsted wool yarn that have been tied with string. Originally this was a black lump of grease when I first pulled it out of the bearing, but I was able to clean it up by soaking it in laundry detergent. A greasy oil wick prevents it from working, and my Wagner’s front bearing was bone dry when I first took it apart. If you’re doing a restoration and you need to replace the wick, you must use real wool. Synthetic fibers apparently do not have same degree of capillary action. Wool wicking is also the material of choice for steam locomotive bearings.

The wick fits in the hole on the top of the bearing.

Here is a photo showing the assembled bearing (minus the washer).

I used a pencil to pack the wick into the bearing. It is now ready for oiling. I am using the 3-in-1 SAE 20 oil that is meant specifically for motors. It does not smell so strongly as the multipurpose 3-in-1 oil. In this picture below, you can see the wick soaked with oil on the fan after final assembly:

Add oil about 10 drops at a time and allow it to soak in for an hour. Do this again until the part of the wick you can see is saturated. If you add too much oil then it could spill out of the top, so you don’t want to add more oil than the wick can hold. It’s important to make sure the wick never goes dry so that your bearing will always be properly oiled.

At the electronics flea market, I found another antique desk fan. This one is a Wagner 9″ oscillator, series M, model 5260, model L53A68. I am not certain when it was manufactured: my guess is the early 1940s.

On the rear of the fan you can see the oscillator gearbox:

Here is a closeup of the fan’s nameplate. It has everything except for the date of manufacture.

This fan is in reasonably good condition, compared to the Emerson that I restored before. There is very little rust which makes the restoration job much, much easier.

So you’ve obtained an antique desk fan, and you want clean it up and restore it, but you just can’t seem to figure out how to get the blades off. Based on a number of email inquiries, here are instructions for removing the blades from certain Emerson antique desk fans. You will need some basic tools, including an Allen wrench, a flashlight, and a wrench appropriate to removing the cage.

Before you begin, you’ll need to remove the cage so you have easy access to the fan blades. Usually that means you need to undo the four bolts holding the cage assembly to the front of the motor casing.
Next, you need to examine the rotor of your Emerson’s motor using a flashlight. Look for a “blind” hole drilled into the side of the rotor. These are drilled by the manufacturer to remove some metal and balance the motor.

Once you’ve found the hole, insert the Allen wrench through one of the vent holes in the motor casing and into the balancing hole on the rotor.

The next photo shows a closeup of the Allen wrench inserted into the balancing hole.

When you do this, be very careful not to damage any of the stator windings. They are very fragile and protected only with a layer of cloth tape.

Once you’ve got the Allen wrench in position, grasp the fan blade by the blade hub (commonly called the “spider”). Yes, the blades will provide more leverage, but they bend pretty easily, and once you’ve bent a fan blade, it will never be the same again.

The threads fastening the wheel hub to the rotor are left-handed, so you need to spin the hub clockwise to unscrew it. The hub on my fan had frozen onto the rotor, and no amount of physical force would get it turning. I trickled some penetrating oil down the hub so it could get into the threads and free things up, but even after that I had to heat up the hub spindle with a heat gun. The heated metal expanded and broke the threads loose. It made a terrible squealing noise when I unscrewed it.

And the blades are off! You’ll want to clean up the threads at this point to remove any crud or rust, and add some oil to make it easy to remove the blades next time.