|The Crosley 124-M "Play-Time" is an 8-tube superhet circuit
radio in a grandfather clock cabinet with an electric clock. As purchased, the radio and clock
were said to work. It receives only the broadcast band.
The radio had seen extensive servicing in the distant past, but no recent restoration judging from the age of the parts used. I decided to attempt to reverse all previous repairs to the extent possible and restore the original above and below chassis appearance. The schematic for this radio can be found on-line at Nostalgia Air.
My antique radio restoration logs
This radio was purchased at the 2012 Charlotte, NC AWA Conference, in the auction. The cabinet was in good original condition, as were the knobs and grille cloth - just the usual wear, dings and scratches. The finish appeared to be oxidized, and very dark, and especially the pressed wood insert in front of the radio and speaker. The radio was sold as working, along with the clock. There was no external evidence that the radio had been restored. Even the line cord and plug were original, and in excellent shape. I always avoid knowingly purchasing a radio that has been restored, as many collectors take shortcuts such as removing the original capacitors and filters.
I have a another example of this radio in my collection with a better cabinet that I had previously restored. This radio was purchased because the wife wanted it to be restored and given to one of our sons (and the price was right at Charlotte!) The last photo in this restoration log shows the original Charlotte cabinet purchased along with the one in my collection for comparison.
All tubes had likely been replaced. Only one tube was a globe type (branded Sylvania), as likely would have been installed originally. Most of the tubes were branded National Union. I am not sure what brand of tube Crosley would have used, but most likely they would have been branded Crosley.
Only two original paper capacitors remained. And it was not 100% certain that these were original, since they did not have Crosley part numbers. But they were the correct early 1930's vintage types.
Most of the bypass capacitors in this radio were originally in two metal clad units, one with two capacitors and the other with four. The dual unit had been removed completely. The quad unit was still in place, but all its lugs had been cut off and tubular capacitors installed, mostly just hanging in space. These replacement capacitors were older units, perhaps circa 1940-1950.
The dual filter capacitor had been replaced by two tubular units under the chassis. The original mounting bracket was still present. This provided a clue as to the size and shape of the original, which was likely a rectangular cardboard-cased unit with wire leads.
Two original resistors had been replaced. Possibly others had also been replaced, but the replacements were the same types as the majority of the resistors (older dogbone types).
My usual restoration procedure is to first make a complete survey of the condition of all components. The survey results guide my restoration strategy. If major and unique components are defective or missing and cannot be restored or replaced, I may elect to sell the radio rather than restore it. I always assume that all paper and electrolytic capacitors are leaky and thus should be replaced (I always "restuff" the original containers if possible). Any mica capacitors are assumed OK until testing proves otherwise.
Before starting any repairs and had to deal with a potential showstopper: the second IF transformer had a open secondary winding. This transformer was quite unique. No trimmers capacitors were used on either the primary or secondary winding. The transformer was removed from the radio for inspection. Here is what is looked like:
I checked where the windings connected to the terminals and scraped and re-soldered the wires - no change. It appears to be some sort of untuned transformer. The IF for the radio is 175 KC. I do not know if this transformer is self-resonant at that frequency, or is simply an untuned transformer. In any case, it would be very difficult to find a replacement. Even if another Crosley 124 parts chassis could be found, it was discovered by reading on Antique Radio Forums that some model 124 radios used a different transformer that DID have trimmers.
With nothing to lose, I thought I would try the same method that I use to repair
open speaker fields: start unwinding the wire until a break is found, fix the
break, and rewind the wire. It first appeared that the GOOD winding was on the outside, naturally. So
I started unwinding it onto a plastic spool mounted in my small Unimat lathe
with the belt removed, turned by hand. My plan was to remove the good primary
winding (which I originally thought was on the outside), unwind the secondary
until a break was found, repair the break, then return both windings to the
original form. But there was a problem - the wire would hang
up on something as I unwound it. THE DARN THING WAS BIFILAR WOUND! AND
WITH TWO DIFFERENT TYPES OF WIRE! One winding was normal enamel wire,
and the other was double cotton covered. I suppose extra insulation is needed,
since one winding has B+ on it and the other one is grounded, and the wires are
side by side and wound at the same time.
So I then started unwinding BOTH windings at once onto a spool, planning to continue until I found a break, repair the break, and then rewind. I did not have to go very far until a break was found. It was repaired, and the wire returned to the transformer. Once rewound and tested, I applied rosin salvaged from servicing RCA Radiola Superhet catacombs to seal the winding (the windings had some sort of wax coating on them originally).
So it looks like the last showstopper to restoration had been removed. Since very little wire was disturbed, it will hopefully work OK. I suppose the purpose of the bifilar winding is to create a very close coupling and broad response (there are no trimmers used).
At this point I made BEFORE photos of the chassis bottom. I use these photos to ensure that replacement parts and wiring are placed as close as possible to their original positions. Some radios are subject to problems (such as oscillation) if wiring is re-routed or lead dress is not the same as the original..
All tubes and the tube shield was removed. The tuning capacitor and dial assembly was removed for cleaning. All non-original parts were then removed and additional photos taken.
The volume control on this radio was original. It shunted the antenna coil primary on one side and the other side varied the bias on the RF and IF stages. In order to provide smooth control of volume in such non-AVC sets, the controls often have three different types of resistance wire. Unfortunately, the control measured open. The usual failure mode is a defective weld or joint between two different wire sizes.
This control was repaired by inserting a paper thin sliver of brass about 1/8"x3/8" (material normally used for model railroad construction) between the two sections of the resistance wire that had previously been joined. The wiper and resistance wire were then cleaned using lacquer thinner and a Q-tip. The repair was successful - the control measured about 4.5K ohms (specifications were 5K) and the resistance varied smoothly as the control was rotated. This was fortunate, since there is really no suitable replacement for this type of control. About the only substitute would be a 5K linear taper potentiometer with switch, or even better, a control with reverse audio taper. These are VERY difficult to find. My old IRC Control Catalogue does show a 10K reverse taper control existed. About the only likely source of one of these would be Mark Oppat.
The power switch was mounted on the back of the control. It was a conventional bat-handled switch operated by an arm attached to the rear of the volume control shaft. The switch was bad - it measured high or infinite resistance, likely due to dirt and corrosion. It did NOT respond to repeated cleaning with contact cleaner, and operation. When I attempted to remove the switch from its mounting bracket, the entire threaded bushing and operating arm separated from the switch body! It was replaced using a bat-handled switch from my parts bin. A slot was cut in the handle to allow clearance by the operating arm. I used a Dremel tool with a cut-off disc, following by smoothing and shaping using files until operation was smooth. The replacement looked somewhat like the original, and worked the same way.
I had restored several of these non-self-starting Hammond clocks before. Hammond Manufacturing eventually became the Hammond Organ Company (not to be confused with the Hammond Transformer Company of Canada). The Hammond Organ used similar synchronous motor technology to spin the organ's tone wheels, which produced the organ tones. My most recent restoration using a similar clock was in an Erla model 271A. To start the clock after a power outage, one must push in on a rear knob and spin counterclockwise, and the speed of the spin is critical! If power fails, the clock must be restarted and reset!
At the auction, the clock was stated as working, and it did. Although starting it was difficult. Once started, it continued to run. I suspected that the mechanism needed cleaning and lubrication. In some cases the motor capsule must be rebuilt - a task for an experienced clock repair shop, since the bushings are likely worn and have to be replaced!
The clock was completely disassembled, and all parts cleaned in lacquer thinner. To keep track of all the various parts, I took photos as the mechanism was disassembled, kept the parts in order through the cleaning process, and made careful notes. Below are the steps of the movement disassembly.
There did not appear to be any pivot holes with excess wear that would prevent the gear train from working correctly - lucky! If heavily worn, or if the pivot holes are oblong in shape or much larger than the pivots, the gears may jam. The pivot holes can be replaced by a clock repairer, but special equipment is needed as well as the appropriate replacement bushings that fit the gear pivots (or can be sized to fit). The movement was quite dirty and caked with hardened and oxidized grease or oil. The pivot holes in the plates were cleaned with wooden toothpicks and/or pipe cleaner soaked in lacquer thinner. The movement was then reassembled and the pivots lubricated with proper synthetic clock oil.
Once assembled, the clock started and continued to run, but appeared to run slowly (which I assumed impossible for a synchronous motor). Left to run, it did not keep time and eventually stopped. I attributed this to an assembly error - I must have installed one of the gears incorrectly. The clock was dismantled and reassembled using the photos (this time I printed them, vs. viewing them on the camera!) The clock then started, ran, and kept time when tested overnight.
I did not mess with the motor capsule - just some lubrication on the front shaft and bushing.
Two original dogbone resistors were out of tolerance by more than 30%, and two measured open circuit. Two were 1/4 watt size, and two were 1 watt size. In two cases (1 meg, and 15K, 1 watt) I had a NOS replacement available that was in tolerance. I collect NOS as well as used dogbone resistors just for this purpose, and buy all I can find on eBay and at swap meets. In two other cases, I did not have a replacement available that was in tolerance. In this case I will find a replacement that is the correct size and has the correct measured value (within 20% tolerance) but not the correct markings! I then repaint the resistor with the value required using hobby enamel paint.
The cathode bias resistor for the 47 output tubes had been replaced by a newer 5 watt wire wound resistor. The original was a large flexible resistor, value 220 ohms (one other flexible resistor was used in the radio, which was good). I found a good wire wound flexible resistor in my junk box that measured 206 ohms and installed that instead. Later, I decided to use the original resistor (which was good) that was installed in the Crosley I previously restored. The 750 ohm B+ dropping resistor had been replaced by an old style tubular carbon resistor. I assume the original would have been a dogbone type. I replaced it with a 750 ohm 1 watt dogbone resistor that measured 880 ohms. The same resistor had also been replaced in my first restoration, so I did not have an original example.
Most of the bypass capacitors in the radio are in two metal cased units with either 2 or 4 capacitors inside. Having restored about four of these 124 chassis, I have found that there are several variations, and none may match the published schematic (the values are almost impossible to read anyway)! You have to restore what you find in the radio. One metal cased capacitor originally held four 0.1mfd capacitors (another example I restored had three 0.24mfd capacitors). This capacitor was still in place (riveted to the chassis and hidden under the second IF transformer), but its lugs had been cut off and four tubular paper capacitors installed in its place:
The metal capacitor was removed from the chassis and its contents removed, retaining the original terminal boards and insulation. This capacitor is installed UNDER the audio interstage transformer, so one must be careful when drilling out the rivets not to damage the transformer! There is no way to retrieve the other end of the rivets without partially removing the transformer. Doing so would likely result in damage to the insulation on the transformer leads, which are VERY fragile. I simply left the remnants inside the transformer, which is potted in tar. The capacitor case and insulation were then soaked in paint thinner and cleaned with old toothbrushes.
One original terminal lug remained. I reconstructed the three clipped off terminal lugs using older type ground lugs having long lugs. The long ends of the ground lugs were inserted through the extant slots in the terminal boards. The terminal boards and ground lugs were then attached to the case using epoxy. Once the epoxy hardened, new 0.1mfd 630 volt film capacitors were installed. One end of each replacement capacitor was soldered to each ground lug on the inside, and the other end soldered to the metal case. The capacitor was then filled with melted rosin/wax salvaged from servicing 1924 RCA Superheterodyne catacombs in order to stabilize the contents. This wax melts at a low temperature and will not damage components.
The other metal cased capacitor, which held two capacitors (0.1 and 0.5mfd), was missing and had been replaced by two tacked in tubular capacitors. This capacitor was originally mounted on the inside rear chassis. I did not have an exact type dud for restuffing. However, I did have a two-lug metal cased capacitor with the correct mounting centers. But its lugs protruded from the side rather than the end. I wished to maintain the original appearance (no visible tacked in components), so this capacitor was used, even though connecting leads and components to the lugs (which now faced downward) was difficult. The capacitor was prepared in much the same was as the other metal capacitor, and restuffed using 0.1 and 0.47mfd 630 volt film capacitors.
Two (likely) original paper tubular capacitors were still in place. Each of these was restuffed using 630 volt film capacitors. One of the capacitors was a Dubilier Cub type, which are difficult to restuff since they have a wooden dowel down the middle! Here is my method of restuffing Dubilier Cub capacitors. The other capacitor, the tone control capacitor (.05mfd, 400 volts, Sprague) was restuffed using this method.
The original filter capacitor had been removed and replaced by two tubular electrolytics. But the mounting bracket for the original capacitor was still in place. This clue indicated the location of the original capacitor, as well as two of its three dimensions! I searched in vain on the internet for a photo of a Crosley 124 with the original filter still in place. There were several different versions of the 124 chassis. I have seen examples that used normal aluminum screw based electrolytics above chassis. My chassis had the holes for mounting these capacitors, but the holes showed no signs of ever being used. The original capacitor held an 8mfd and 6mfd electrolytic. The voltage rating is not documented, but would have to be at least 400 volts. The original capacitor likely had wire leads, and was definitely rectangular in shape. It was probably a cardboard cased unit.
Using the extant mounting bracket for dimensions, I formed a cardboard case using thin cardboard from the back of a writing tablet. Two 10mfd 450 volt electrolytics were mounted inside, and wire leads attached and routed through a hole in the cardboard case. The cardboard case was assembled using carpenters wood glue and rubber band clamps. The finished case was then painted using aluminum enamel. A label was fabricated using the correct Crosley part number and values. The Cornell Dubilier brand and logo was used, since one of the original capacitors was a CD brand Here is the result (the clamp is original):
A new #41 pilot lamp bulb was fitted. The visible shouldered tubes (80, and both 47s) were replaced by globe types 280 and 247, since this chassis would be swapped into my better condition cabinet and become the keeper. The tube shield hides the other tubes, which were not globe types.
The cabinet only needed a good vacuuming inside and then cleaning on the outside with GoJo and 00 steel wool. It turned out definitely presentable, but not as good as my keeper cabinet.
Once the radio chassis was reassembled and the tubes installed, power was brought up slowly using a variac. AC power consumption was monitored using a watt meter, and a DVM monitored the B+. The radio powered up and worked immediately. The radio was then aligned. The radio performs well, is quite sensitive and has very good tone. The rebuilt volume and tone controls works smoothly.
I was able to successfully reverse all previous repairs and restore the likely original appearance of the radio under the chassis. Of course, I did not know the exact appearance of some of the original parts. I have yet to find photos of an original under-chassis view of the Crosley 124 before any repairs or restoration. The replacement filter capacitor was the correct size for two dimensions, but the third (length) was just a guess.
This chassis and other components of this radio were swapped into my better condition cabinet, and would become my keeper. The original Charlotte cabinet and the chassis from my own original 124M would be given away to one of our sons, or else sold. The Charlotte chassis was more original than my first Play-Time: the audio driver transformer and volume controls were original. The cord on the clock had the attached socket for plugging in the radio. The Charlotte example had an original Crosley "Tennaboard" antenna installed on the inside of the cabinet. This was moved to the keeper cabinet. The ST type 47 and 80 tubes from the Charlotte chassis were installed in the give-away/sell chassis. The clocks were also swapped between units (both were working, but the keeper had the attached socket for plugging in the radio). While both radios and clocks worked, my "keeper" chassis sounded much better and the original volume control operated more smoothly. The original audio driver transformer in my keeper sounds infinitely better than the other chassis, which was fitted with a Stancor A-73C transformer. Due to much lower primary inductance of the A-73C, distortion is noticeable.
Keeper - My Cabinet
Keeper - My Cabinet