The Philco 40-201 uses a 36-1450 field core speaker. It appears that the DC resistance is 860 ohms and that the current through it is 122ma with a voltage drop of 105 volts. The power dissipation is about 12.8 watts.
What is the impedance of the voice coil? Its DC resistance is not shown on the schematics I have. The OEM speaker is missing so I may need to use a PM replacement until I can get an OEM unit to install. Voice coil impedance may not be much of an issue except for power mismatch if a replacement speaker is way off.
One thing you may want to do is check the primary of your OT. It's common for them to go open. If it is OK then the closest thing you'll find will be a 3.2 ohms replacement. The original is 1.25 ohms.
GL
Terry
OK, thanks for that input. Yes the 3.2 ohm impedance was quite popular in many radios of the late 1940s and the 1950s. I will check the output transformer as you suggested. I just finished taking a lot of pictures of cabinet and chassis. On the 40-201 the output transformer is mounted under the chassis instead of on the speaker, so at least the transformer is still there even though the speaker is long gone. I will have to decide whether to find an OEM speaker & field coil assembly or to substitute a DC choke in the power supply and use a PM speaker. I have several 12" PM speakers on hand that are 8 ohm speakers. There is much to do before I ever get to the point of chassis work. The cabinet will probably consume much of my time until colder weather hits and drives me back into the house instead of the barn.
An ultimate solution might be to use a new output transformer small enough to mount in the existing position designed to operate a 4 ohm or 8 ohm PM speaker. A transformer designed for a push-pull 6V6GT output stage would also work for the push-pull 42 tubes.
All the chassis and tubes were covered with dried mouse pee. I took the time to remove tubes one at a time and cleaned them with a soft brush and water being careful with the lettering. Naturally some of the old painted on lettering did come off, especially on the Loctal Philco OEM tubes in the front end and IF/Audio Detector circuit. The other tubes were somewhat easier to clean and all of them did have etched IDs on either the top of the glass or on the side. I managed to get the pee and debris off of the IF transformers and the electrolytic filter capacitors. The electrolytics are original, so they will have to be replaced first. I did look at the audio output transformer and found that it has already been replaced some time in the past. The transformer that was used is a Stancor A-3823. I will have to look that one up to see what its ratings are. Just looking at the illustration of the underneath of the chassis in Ryder publications, it appears physically smaller than the transformer that Philco used. I did check the replacement audio transformer and it does have continuity plate to plate of the 42 tubes.
This chassis has 4 rubber cushions that are at the corners of the chassis. So far I have not located cushions that look like these in my searches.
I am not sure if the radio originally had an on/off switch using the first push button or not. This radio had a toggle switch that was mounted in the cabinet just at the top of where the speaker baffle is mounted, but is in a vertical hole up through the wood of the horizontal bracing. The switch points downward and is hardly visible unless you really look for it. I found this when the chassis would not come out after all the chassis screws were removed and the two dial plate screws had been removed.
I will post some photographs.
Joe
(This post was last modified: 11-18-2013, 11:04 PM by Joeztech.)
Thank you very much. I was on the right page, but just had not scrolled down far enough. I will be ordering those plus a set of push-buttons. The rubber washers for the tuning capacitor front end area also need replacing. I am so glad that there are people who have created a business supplying such hard to find parts. I even spotted one site that has some grill cloth that is very close to the original pattern of the 40-201 cloth.
I have seen some of your other posts and you do a great job restoring these radios!
Today I spent time cleaning the chassis top side. I used some citrus aroma waterless hand cleaner along with a fine bristle stainless steel wire brush. With the tubes removed I worked on a small section at a time. I took the power transformer top cover off and used the wire brush on it plus some sand paper where the rust was worst. It cleaned up nicely and then I followed it with a black gloss spray epoxy paint. The cover was then put in a toaster oven to speed up the drying process. I noticed that the transformer cover has the Philco name on it and the part number also appears on it. With the transformer cover off the top insulation over the internal windings also has the transformer part number imprinted on it.
The one area of the chassis that did not clean up very well was the area under the dial where the two electrolytic capacitors are mounted plus the area around the two IF transformers. I will order axial lead electrolytics to use in rebuilding the existing electrolytics. Each one is an individual electrolytic with no other sections in the case. That will make rebuilding the capacitors easier.
I also took time to clean the dial knobs by removing them. The hardest ones to remove are the tone and volume control knobs. It takes a little study to realize that the only way they will come off is to loosen the volume and tone controls from the chassis enough to allow enough play to get the knobs off after the outer shaft bracket is removed. Reassembly is somewhat tricky as the tone and volume controls both have to be adjusted so that both work smoothly. I also lubricated the control shafts.
The tuning capacitor assembly needed lubrication, so I did that while the knobs were off. I did not want to turn it until the lubrication was renewed.
Most of the rust is now gone and I will do some additional cleaning of the chassis top when I get the Electrolytic capacitors off for rebuilding. The mice had built a nest underneath the dial and control/push-button assembly and in front of the tuning capacitor. They chewed completely through the wires to/from the tuning capacitor and the push-button preset coils. I will be ordering some hook-up wire in multiple colors to take care of that. I will be looking for some wire with identical colors if at all possible. Solid color wire is fairly easy to find, but not the wire that has a base color plus a stripe. Some homework lies ahead on that.
Do you have the field core speaker you mentioned for this 40-201?
I will order electolytics tomorrow and an 860 ohm wirewound resistor to sub for the field core for now. That will keep the voltages the same as when equipped with the field core.
I will be removing the electrolytics for stuffing with new parts tomorrow. That will give me a chance to also remove the IF transformers and finish the chassis cleaning, then spray with silver color paint to protect it.
Yup, seeing your latest reply triggered my memory...yes, I did look for, and did indeed find, the 12 inch speaker I said that I had. The field measures 803 ohms, the voice coil, around 4.5 ohms. There is a crack in the cone, easily repairable with fabric glue. Yours for the cost of shipping if you want it. Let me know.
Today I removed C78 and C77. C78 was a Cornell Dublier replacement from some time in the past. Whoever installed it put the screw head of the hardware on the mounting clamp against the left side of the bracket that supports the control and push-button assembly. Because of that I found it very difficult to remove C78. I finally clipped the leads going to the volume and tone control and removed the control assembly. Mice had already chewed the wires going to the push-button coils. The bottom end of C78 had a cardboard sleeve between the can surface and the inside of the holding bracket.
I cut C78 and C77 open using a tubing cutter after removal from the chassis. C77 was the original Philco wet type capacitor. C78 had a large nut and washer on its bottom and the plastic threaded stud broke off as I was unscrewing the nut. I will have to use some epoxy to glue it back together. The internal parts of C78 were embedded in a hard wax or tar material. I had to use a hair drier to soften it enough to get the capacitor element out. I used a 3 inch long deck screw to pull it out.
C77 was completely dried out when I opened it up. I did find that a 1 inch PVC tube fit snugly inside this electrolytic's can, so that will be used to provide strength when the capacitor shell is put back together with a new axial lead electrolytic inside. The + and - leads will be brought out through the hole left in the bottom part of the old capacitor shell when it is remounted in the chassis.
I cleaned off the chassis where the two electrolytics and the control bracket had been. New rubber grommets will be needed for the control assembly mounting to the chassis when it goes back together.
(This post was last modified: 11-21-2013, 07:03 PM by Joeztech.)
Here is a picture of the chassis after C79 and C77 were removed and the chassis was cleaned with a wire brush and some waterless hand cleaner with pumice in it.
Today I took the remaining IF transformer off the chassis. I took the internal parts out and put new wires of the right color code on using stranded 22AWG wire of 600V insulation. I need to attach similar wire to the other IF transformer that I repaired. Unfortunately I did not have the wire when I reassembled it. So, I will have to attach new leads near the bottom somewhat inside the shield and use some heat shrink tubing to keep them insulated.
After I got the last IF transformer off I took more pictures and removed the tuning capacitor. I also removed the one trimmer cap that has its stud above the chassis. There was considerable corrosion in the chassis metal at that spot due to the mouse pee. With all these parts off, I scrubbed the rest of that end of the chassis once more with waterless hand cleaner with pumice in it using the find stainless steel wire brush. It cleaned up pretty well.
There is some remaining corrosion where the mounting clamp for C78 was located. I may go ahead and drill out the rivets that hold the clamp on and clean the chassis there too. If that is out of the way, the only other thing still left in place would be the power transformer. I may go ahead and remove it too. That way I can completely clean the top of the chassis in preparation for spray paint.
This radio chassis has an ink stamped ID on it saying:
Model 40-201 (the 1 is almost eroded away)
Code 122
And there is stamped into the chassis metal U87162, which I assume is the serial number of the radio.
In the photographs you can see the area where the tuning capacitor was mounted. That area is cleanest.
This chassis has a jack on the back to plug in a phonograph plus a toggle switch next to it. This appears to be a factory option, not an add-on done later. The bakelite plastic around the jack actually says Phonograph Pickup and is a 1/4" phone jack type that interrupts one set of contacts and makes another. Since that is the case, I wonder why the switch. I need to trace this out and see what they really did to the circuitry.
(This post was last modified: 11-23-2013, 01:45 PM by Joeztech.)
