|The Crosley 146 from about 1932 is a 9-tube superhet with a
tuned RF amplifier and two IF amplifier stages. It receives only the
broadcast band. The chassis is very complex and features a
sophisticated AVC system with sensitivity control, push-pull class B
output stage, a tuning meter, choke input filter power supply with mercury
vapor rectifier, and both 2.5 and 6.3 volt filament tubes!
The schematic for the model 146 is in Riders Manuals page 3-23, but is NOT on-line on Nostalgia Air. Here is a scan of the schematic from Riders. Any parts references will be to this schematic. It is interesting that my chassis was actually factory stamped 146-1 rather than 146. The 146-1 chassis is used in consoles with two speakers. My chassis is definitely a 146 based on parts values used. Also, my chassis was factory stamped "Senator" on the back The Senator models in RadioMuseum are consoles. I was told by another collector that this particular cabinet style is more rare than others.
The radio had seen minimal servicing in the past - most of the original parts were still in place. I decided to try to reverse all previous repairs to the extent possible.
My antique radio restoration logs
This radio was purchased at the 2011 Charlotte AWA Radio Conference. The cabinet was in good original condition, but with some veneer bubbles (due to failed glue) and finish loss on the top and sides. The cabinet arch support had been secured using small nails! The knobs were original and in good condition. The grille cloth was torn. I always avoid knowingly purchasing a radio that has been restored by a collector, as many take shortcuts such as removing the original capacitors and filters. No repairs were obvious at the time of purchase, and the AC cord was original and in poor condition (possibly preventing someone from "testing" it before sales). The original tube shield was still in place - it is often missing since it must be removed in order to service most of the tubes (if this were missing, I would not have purchased the radio).
One original filter capacitor (parts 23 & 24) had been removed and had not been replaced. The other original filter capacitor (part 54) was still in place, but disconnected. A tubular 16mfd/450 volt capacitor had been installed for part 23 (a 6mfd low voltage capacitor). It appeared to me that someone had attempted to repair the radio but never completed the repairs. That can easily happen due to the complexity of the chassis and difficulty reading the schematic. The replacement capacitor was an older type service replacement, so the attempted repair likely occurred in the distant past.
Capacitor 31 (0.1mfd) had been replaced by a 0.015mfd/1600 volt capacitor - also an older Sprague replacement type.
Several tubes were not branded Crosley and thus were likely replacements
The AC line fuse had been removed (3 amp, I assume it was a fast blow type)
The AC plug was a replacement (rubber).
The bottom cover was missing. Fortunately, the original tube shield was in place!
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 doing any repairs I had to deal with the two potential showstoppers: the open speaker field and open tuning meter. If these could be repaired, I would proceed with repair and restoration. If not, I would probably sell the radio for parts. Fortunately, both issues were resolved!
Before starting repairs 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 tube shields were removed. All non-original parts were removed. The tuning capacitor and dial assembly was removed for cleaning. This radio uses quite a few 8-32 square headed screws. A 7/32" 8-point socket (1/4" drive) is needed to remove them in some cases. Even with the socket, removal was difficult in some cases, as the screw heads are slightly tapered!
The top and sides of the chassis was cleaned with GoJo hand cleaner and 00 steel wool. Since this process may leave small steel wool fragments that can cause problems later, I follow up with a thorough vacuuming and go over everything with a small magnet and masking tape to pick up any stray fragments. I continue to use steel wool as I have yet to find a substitute that does as good a job removing the "gunk".
The tuning capacitor was cleaned in my old Heathkit ultrasonic cleaner followed by soap, water, and toothbrushes. It was then dried using a heat gun. The bearings were then lubricated using distributor cam lubricant (which is similar to the original grease used). Before cleaning, the trimmer micas were removed in order to prevent damage. In order to get the trimmers back to approximately where they were originally set, I first note the position of the trimmer screw on the clock, then count the half turns (and fractions) from that position to fully tight. The mica sheets and trimmer hardware were also cleaned in the ultrasonic cleaner and then dried before reassembly. After reassembly, each trimmer is again turned to fully tight position, then backed off the appropriate number of half turns and fractions. This process will return the trimmers to close to their original positions (later fixed by a full alignment). The rubber tuning capacitor suspension grommets were somewhat stiff and had shrunk. They were replaced with exact replacements available from Renovated Radios - part GLg-Crosley).
Insulation breaks in the speaker cable were repaired using shrink tubing over individual wires that had breaks, thus retaining the original cable. My repair process is to unwind one wire at a time and install shrink tubing over any breaks. That wire is then wound back onto the cable before the next wire is removed and repaired. Three of the four leads required repairs. The power cord was replaced using reproduction cloth covered AC cord and an old style round AC plug - the original power cord had virtually NO cloth covering remaining, and the plug was a rubber replacement.
A 2 amp fast blow type 3AG fuse was installed in the fuse holder. The schematic called for a 3 amp fuse, which I did not have in stock. I thought I would first try a 2 amp fuse, since this radio was not going to be a daily driver! With 110 volts in, the radio only drew about 65 watts.
Servicing this radio is very difficult. It appears to have been built in layers. Many components are buried beneath the controls or other parts. And one must avoid any damage to the stiff and brittle flexible resistors when making repairs.
The speaker field coil was open. Fortunately, the field coil assembly was attached to the speaker basket with bolts, and was not riveted or welded (these types are really not repairable without extreme expense). The coil was removed and examined. The outer insulation had been disturbed in one area, indicating that someone had perhaps attempted to repair the field coil previously. When I removed the coil I took careful notes so that the parts could be reassembled and wiring reattached exactly as originally found. One potential problem that arises when a field coil is removed is re-centering the voice coil on the magnet core during reassembly. Fortunately, in this case the center core passed through a bracket that fit very tightly around the core. This bracket was attached to the speaker basket and voice coil spider, so that the core would automatically be centered upon reassembly. Most other speakers I have worked with required shimming the voice coil, plus lots of trial and error to ensure that the voice coil is properly centered. And some speaker repair businesses insist on reconing the speaker if the field coil is disturbed.
The outer insulation was removed from the field coil. The wire connections were OK - sometimes one gets lucky and the problem is a break or corrosion at the point where the external wire leads attach to the coil. No such luck here. Next, I connected one lead of my DVM to the inside lead, and probed the outside of the coil with a sharp #11 Exact knife blade connected to my DVM. Sometimes the break is near the outside, and only a small amount of the original winding needs to be removed in order to restore continuity. No such luck here - the break was obviously deep inside the coil or perhaps the lead to the center of the coil was broken. In any case, the coil would have to be rewound.
One problem with a rewind is finding the correct size and amount of magnet wire needed. Checking with a micrometer and my Handbook of Physics and Chemistry, it appeared that the wire gauge was about 38. The coil resistance was supposed to be 2300 ohms. I decided to first attempt to reuse the existing wire by unwinding it until a break was found, repairing the break, then rewinding using the original wire. I chucked a plastic spool which originally held hookup wire (the type sold by Antique Electronic Supply) into my Unimat lathe 3-jaw chuck. The field coil was mounted in a fabricated holder using a large wooden dowel with long self-tapping screws in each end, held by a metal bracket formed from bent up metal strapping. The bracket was screwed down to my work bench. The holder allowed the field coil to rotate freely.
The start of the winding was then attached to the plastic take-up spool and the unwinding process started. I ran the lathe at its slowest speed, and left the belt cover open and my hand on the pulley so I could stop the lathe instantly if there was a tangle or break. It was interesting that during the unwinding process, there were actually several original splices found in the wire! The wire had been stripped, twisted together, soldered, and the joint insulated using what looked like paper tape. All the wire was removed from the field coil, and no breaks were found, so the break was likely in the lead from the center of the coil.
The process was then reversed by chucking the field coil spool in the Unimat lathe, and mounting the supply spool in the fabricated holder. The winding direction had previously been noted, along with which original field lead went to which end of the coil! It is important that the relationship between the field coil, voice coil, and hum bucking coil be maintained. The coil was thus rewound using its original wire. It measured about 2300 ohms when completed, which was correct (hardly surprising since the original wire was used). New wire leads were attached (the originals were very stiff and brittle). The coil was wrapped first with black friction tape. Black vinyl electrical tape was used to secure and insulate the wire connections to the coil. Finally, another layer of friction tape was applied
The coil was reinstalled in the speaker and the connections between the field coil, connection terminal strip, hum bucking coil, and output transformer were restored. As previously mentioned, after reassembly the cone was properly centered and did not drag or scrape on either side of the gap. The speaker was then tested by driving the voice coil from another radio and the field coil from a DC supply consisting of a Variac, 1N4007 diode, and 200mfd/160 volt filter capacitor. The speaker worked properly with the Variac at about 30 volts AC input and there was no further improvement in volume past that point (I did not know the actual voltage across the field coil at this point). The speaker sounded GREAT!
The tuning meter coil was open. The meter mechanism was first removed from the outer metal shield by pulling on the leads and attachment clip. The meter movement is held inside the cover/shield only by friction, but can be difficult to remove. Once apart, the coil was exposed. The wire leads were first unsoldered from eyelets on a terminal board and removed, hoping that there was a break where the leads attach to the coil. Checking the coil at each end, there was no continuity. I then tried to probe the coil for continuity from the outside using an Exacto #11 knife blade, hoping that the break would be near the outside. In that case, it could be restored with minimal loss of turns. But no luck! So I was faced with rewinding the coil.
Before the coil could be rewound, the meter mechanism had to be removed from the center of the plastic coil spool - I was not comfortable spinning the delicate meter mechanism at high speed! There is a single screw holding everything together. The screw goes first through a terminal board, then through the plastic coil spool, through a piece of fish paper insulation, a horseshoe magnet, into the metal base of the mechanism. HINT: note the position of the horseshoe magnet - it needs to be returned to the original position! In my case, not knowing there was a magnet there, it moved during disassembly and I was forced to find its correct position by trial and error later (the pointer should be to the far left looking down toward the coil winding at rest). The meter movement can then be gently pulled from the center of the coil spool. In so doing I disturbed the pointer adjustment and was faced with a VERY difficult set of adjustments once reassembled, in order for the meter pointer to move freely.
All the existing wire was removed from the spool by use of a sharp Exacto knife with #11 blade. I measured the wire using a micrometer, and it appeared to be about #40 gauge. Fortunately, I had a small spool of #40 wire in stock (purchased from Antique Electronic Supply, although I don't think they stock it any more). I did not know the correct resistance of the coil, so I decided to simply note how much wire was originally on the spool and duplicate that as close as possible.
I was able to chuck the flat projection of the plastic coil spool into the 3-jaw chuck of my Unimat lathe directly. I used the same holder for the wire supply spool as I used when the speaker field coil was rewound. I was not able to determine the winding direction, so I decided to just wind the coil and later reverse the leads if the meter deflected in the wrong direction. There was a small hole in the coil spool for the start of the winding. I then simply wound the spool until full (to the approximate level as originally found). The meter was then reassembled and tested using a battery. A 1.5 volt battery would deflect the meter about 25%. At this point I did not know if the meter would work properly in the radio. I did know that the polarity was now incorrect, and that I would have to reverse the leads when the meter was reinstalled in the radio. If the meter was too sensitive, I planned on adding a shunt resistor if necessary.
The combined tone control (part 14) and power switch (part 16) was of the Allen-Bradley Bradleyometer type, which is difficult to repair or clean. These controls have a unique appearance, and thus it is critical to restore them if possible. My process for restoring them is as follows:
The volume control (part 13) measured about 3.5meg (spec was 3 meg) but was hopelessly worn and would have been scratchy in use. I could tell by measuring the resistance as the control was rotated - the meter jumped all over the place and did not move smoothly (I use an old Knight analog VTVM for testing volume controls, noting how the pointer moves as the resistance is increased from minimum to maximum resistance - it should be smooth with no jumps). I removed the back cover and gave it a quick shot of control cleaner. This only made things worse - the control now measured 7.5meg! It was obvious that the thin carbon layer (on a paper base) was badly worn. This type of construction really cannot be cleaned up. The original control was large and distinctive - bakelite - so I did not want to simply stick in a new replacement control. So I decided to try and rebuild the original unit.
I found that a new IRC Q-type control would just fit inside if the existing wiper, brass bushing, and resistance element could be removed. The control had a D-type shaft that would accept the original knob. It would have to be cut to length afterward. I removed the C-clip retaining the original shaft and wiper. The brass bushing was then drilled out using a succession of drill bits in a small drill press. Some of the bakelite was also removed, leaving a 1/2" hole in the center. Some bakelite projections inside the control were also removed to provide as much space as possible for the new control. The original wiper contacts were cut short, leaving a minimal amount of metal. The remnants were cleaned and tinned, and short buss wires were attached to each. A NOS IRC Q13-139 control was fitted inside (2meg, audio taper), and the buss wire leads soldered to its lugs. An original nut held the new control in place. The new control's threaded bushing was just long enough to allow a nut to be attached once mounted in the chassis. It was necessary to increase the diameter of the center hole to just over 1/2", and to chamfer the edges, in order to clear the new control's bushing shoulder and provide the maximum bushing projection length.
|With the attachment nut still in place, the new control was secured to the old control's case using dabs of epoxy over its flattened locating tabs. The original metal back cover was then secured in place using a dab of epoxy to the metal back of the new control, since the depth of the new control kept the back cover from completely seating (originally held in place by bent over tabs). The new control was supposedly 2 megohms, but actually measured 1.8 megs. In the original radio, there was a 1 megohm resistor (part 82) from the wiper to ground. It had drifted to about 1.8 megohms. It was left in place, since the replacement potentiometer was lower resistance than the original (at full volume, the original parts would measure 750K. With the new parts, the measurement would be 900K).|
All original paper capacitors were rebuilt in their original cases using modern 630 volt axial film capacitors in order to maintain the original under-chassis appearance. I reseal the original cardboard tubes using rosin salvaged from RCA catacombs (it melts at a low temperature and will not damage the replacement capacitors). I collect original branded wax/paper capacitors (Zenith, Philco, RCA/GE) for use when the originals are missing or have been replaced. Most of the capacitors in this radio were of the Dubilier CUB type. Most of them were dual units, with a center mounting ring that is common to both capacitors. Here is the procedure I use for restuffing these capacitors. One original CUB capacitor had been replaced (part 31). I did not know its original voltage rating - voltage rating is not listed on the schematic in Riders. But the highest marked voltage found in the radio was 400 volts. It was replaced using a dud 0.1mfd/400 volt CUB capacitor from my spare dud capacitor stocks, restuffed with a 0.1mfd 630 volt film capacitor.
In order to restuff the dual 0.1mfd units, it is critical that the replacement capacitors be small enough to fit inside the original case end to end. Many 0.1mfd 630 volt film capacitors sold by Antique Electronic Supply and Radio Daze are much too long. I was able to buy suitable capacitors from Mark Oppat while at the Charlotte AWA Radio Conference. These were made by Richey Capacitor Inc. (Taiwan), type PEMT, and are only 11/16" long. To restuff the dual CUB capacitors, I first remove the original contents and unsolder and remove the common ground braid which is soldered to the mounting ring. I then drill a 1/16" hole in the mounting ring and route the ends of two replacement capacitors through the hole. The metal end caps are then attached to the projecting leads as documented here, and the cardboard covers installed. Once the capacitor has been sealed using rosin and tested, the common leads are soldered to the center ring and then excess wire cut off.
The power supply input filter capacitor (part 54) was removed and restuffed. The original was 12mfd (voltage unknown, but under load the B+ voltage at that point is 350 volts). It was restuffed using a new 15mfd 450 volt electrolytic I had in stock. Since the power supply filter is choke input, the slightly larger filter capacitor should not matter that much. The capacitor can was chucked in my Unimat lathe and its case scored about 1" from the bottom. The cut was then completed using a hobby razor saw and the edges cleaned up using an Exacto knife. The original contents were then removed and the capacitor case cleaned inside and out. The insulation on the center positive terminal was crumbling and the stud was loose - I simply did not trust it. So I removed the center stud, external terminal, and insulation. All of this was replaced by a long 6-32 screw with ground lugs on each end - one for the new capacitor inside, and one for the external connections outside. Suitable insulation was fabricated using plastic bushings, spaghetti insulation, and fiber washers. The negative lead of the new capacitor was extended, insulated, and then routed though a small hole drilled into the capacitor base and wrapped around the screw base, thus making contact with the chassis. The two halves of the case were then joined together using a plumbing 3/4" PVC pipe coupling wrapped with masking tape, and epoxied to each section. The masking tape is needed since the couplings are slightly too small in diameter. It also should make it possible to disassemble the capacitor in the future should that be necessary.
|Restuffed Input Filter Capacitor (part 54)
Restuffed Dual 0.1mfd Dubilier Cub Capacitor
Restuffed 0.1mfd Dubilier Cub Capacitor
One original filter capacitor (parts 23 & 24) had been removed and not replaced. I had no idea what it looked like, or even where it was originally mounted under the chassis. I did find the remnants of its lugs at some point, and there was a slight shadow on a vertical bracket near the filter choke where the capacitor may have been mounted. The bracket accepts a screw that holds the bottom cover in place (which was missing). This information provided at least a hint as to the size and location of the capacitor. Inquiries and searches on Antique Radio Forums, Radiomuseum.org and the news group rec.antiques.radio+phono plus Google searches turned up no information. I was able to contact several collectors who had restored this chassis but they did not remember any details about the capacitor. So my only choice was to fabricate something that could possibly be similar to the original. I fabricated a cardboard case measuring 3.5" long x 1" x 1.5" from "shirt cardboard" painted with Aluminum enamel. This size would fit under the chassis and not interfere with existing wiring or other components. The original capacitor was 12mfd (high voltage) and 6mfd (low voltage). I used a 15mfd/450 volt capacitor for the high voltage, and a 10mfd/50 volt for the low voltage. Ground lugs were attached for terminals. A mounting bracket was fabricated from thin metal. A paper label was created using a scan of the logo from a Cornell-Dubilier filter capacitor. The original wiring was reconnected to the lugs, which indicated that the chosen location must have been approximately correct.
The oscillator coil padder capacitor (part 33) was a Sprague .0015mfd/400 volt unit marked with a Crosley part number. It was different in appearance from all the other capacitors in the set, and I hoped it would be good! But no luck - it was VERY leaky. Unlike the other capacitors, which were sealed with wax, this one was sealed with TAR! I first tried to melt the tar out of each end, but the innards would not budge. I had to somehow be able to restuff this capacitor without destroying the cover. Next I tried to heat it up using a heat gun on high heat. I was able to first remove the label, but with some damage. Next I unwound the thick paper which made up the cover - it was similar to the gray fish paper sold by Antique Electronic Supply. I removed the contents and as much tar as possible using paint thinner. This capacitor was an ordinary foil-paper capacitor - nothing fancy. There was a small fiber strip with small holes inside which guided the radial leads of the capacitor. This was reused to form the bend in the leads of a 0.0015mfd/630 volt film capacitor. The capacitor was then wound with strips cut from paper towels, until the thickness of the assembly was approximately the same as the original capacitor. The leads were then passed through extant holes in the cover, the cover would around the assembly and glued back together with service cement. Once dry, the cover was held in a vice to form the original oval shape of the capacitor, and the ends were filled with melted rosin. The original label was then reattached.
All resistors were either 1/4 watt dogbone types or flexible wirewound units. Several of the flexible wirewound resistors had outer cases that had broken. The insulation was very stiff and fragile, and would break if any pressure was applied. However, all of the resistors were still good. These were repaired by covering the break and reinforcing the cover with two layers of shrink tubing.
There were 8 dogbone resistors that were hopelessly out of tolerance - some as much as 100%. All were 1/4 or 1/3 watt. I found NOS replacements for several of these in my parts stock that were actually in tolerance. For the others I needed, I found replacements in my parts stock that had drifted in value to within 0-15% of the needed value. I collect all the NOS and used dogbone resistors I can find just for this purpose, and never throw a dogbone resistor away. These resistors were then repainted to the needed values using hobby model paint. For example, one resistor I needed was 150K. I found a 100K resistor that had drifted to 160K. This as repainted by painting the end GREEN.
The cabinet needed a good vacuuming inside and then cleaning on the outside with GoJo and 00 steel wool. This was followed up using Old English Scratch Cover which did cover some scratches and dings. The loose veneer and some delamination was glued and clamped. I could not find anything close to the original grille cloth from my usual supplier, grillecloth.com. Plus, because of the size needed (16" x 12") a large piece would have been required. I found something suitable in my stock and used that.
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 came to life immediately and worked. It was then aligned. The radio is quite sensitive and also has good tone. The sensitivity control works well. The tuning meter functioned properly, but needs a strong signal in order to get any significant downward deflection when tuning. But my antenna was a simple 20' length of wire strung across my basement ceiling, and in addition I am located in a rural area. There are no strong AM stations nearby. I suspect that the radio was designed for a long outdoor antenna and ground to work properly. This was confirmed during alignment, when a strong signal from the signal generator would dip the tuning meter strongly.
I found that is was not possible to monitor the AVC action other than by observing the tuning meter. Even a modern DVM connected to the AVC line would kill reception totally. This is likely due to the way the circuit is configured. The RF and IF amplifier tube cathodes are connected to B+ through resistors, and thus are at a high positive voltage. The AVC voltage fed to the grids is also positive, but at a lower voltage than the cathodes. Any load on the AVC line, even 10 megohms, will reduce the grid voltage significantly and thus cut off the RF and IF amplifier tubes.