After about a year since I introduced myself with an incoming Philco 91H, Code 126 it is finally time to see what I’ve gotten myself into.
As mentioned in my introductory topic I am not new to vintage radios but this is the oldest and first Philco I’ve had in the shop. The information I have found on this site has been extremely helpful and after learning about the bakelite blocks and condenser banks I’m ready to assemble a list of parts needed.
At first look it appears to be unmolested but I have seen a few things that make me think it may have been in the shop sometime in its life. The transformer is HUGE!
My plan is to first replace the electrolytics, check the input transformer for proper continuity before applying any power using a dim-bulb tester.
-> The electrolytic capacitors
- are both 6uf 400v, P/N 4916 in the schematic but are different cans with a 8095 on one and the other, which appears to be copper, the label peeled off at one time - I suspect the shorter silver one is a replacement
- I plan on using 6.8uf 450v as replacements
-> The Bakelite Blocks and Metal-cased condensers
- there are nine of them and will heat to remove the tar but is it recommended to do this with the metal-cased condensers?
- I plan on using safety caps in the one connected to the input lines
-> Line cord
- This looks to be original and in good shape but I think the plug has been replaced, is it SOP to replace line cords?
- What would the original plug look like?
-> Cleaning tuning dial
- It’s quite yellowed but unbroken. I do not see any way to remove it without disassembly of the tuning capacitor so will some gentle cleaning lighten it up.
-> Speaker cloth
- I found a good match at Radio Grill Cloth, #1 looks to be a close match
Well, that’s enough for now. I’m hoping the shadow meter works but that will come much later.
will heat to remove the tar but is it recommended to do this with the metal-cased condensers?
They have a cardboard liner inside so sometimes you can just put the innards out after sniping the gnd wire. Or the tar will glue the cardboard to the tin.
Cord and plug
The last cloth cord I got was from amazom. I think it was listed in the lamp/lighting section. 7' long and abt $7 has a modern polarize plug. You can easily clip it off. The old skool plugs are commonly referred to as acorn plugs. As a side note Philco used cloth cords till '37.
Cleaning tuning dial
I would use Qtips and odorless mineral spirits. Never use water or soap&water. This will remove the print from the dial.
I’m hoping the shadow meter works
Generally the big issue with the sm is the internal coil being open. Easy to measure the coil resistance which should be abt 1k or so. If it's 100k you'll need some 40G magnet wire a 3" 1/4 20 bolt and nut. Oh some sets have a carbon resistor in parallel w/the coil so that needs to be out of the circuit to get an accurate reading. Said resistor is on the chassis not inside the meter housing.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 12-22-2024, 06:46 PM by Radioroslyn.)
All the bakelite blocks have been recapped. I found that using a heat gun and skinny screwdriver allowed me to push everything out easily. Same goes with the condenser cans but removing the block and replacing the caps in the tone control took a bit of trial and error.
So now I have a working audio section and have started working back through the IF and RF sections.
Is there a way to disassemble, without breaking, the volume control to clean it out? It's pretty scratchy.
It does not require taking apart.
Find an opening, any gap that would lead inside, where the resistive element and the wiper are; take the Deoxit F5 (important. Not D5. Never use contact cleaners on pots), which is Fader Lube, and spray inside that gap; then work the wiper. You could repeat it.
Let dry.
Use thereafter.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
When it comes to the cloth covered power cords, if they are not frayed, and are flexible, and if I can bend one without hearing any cracking noises, I reuse them. It's only 120 volts, and there isn't any real amperage being drawn through them, maybe 1.5 amps on a big set, cord was rated for 10 amps when new. If you want a more suitable plug for it keep your eyes open in the second hand stores, or in a junk plie, for a cap style plug on something. I've ended up with them from random pieces of junk, appliances, and old lamps, they sold them in hardware stores for years, probably well into the 1980s.
As for cleaning the dial it really depends on the year, the 1936-38 ones had a water soluble ink on them, on a 1932 model I'm not sure. The one on my Philco 60L was NOT water soluble, neither was the dial on the model 96, I always test them in a spot where it it will not be seen, like the first line on the low end of the dial, around where the eyelets are, a little water on a q tip, if some of it comes off you can always draw it back in again with a fine tip marking pen.
Regards
Arran
Just to make it more confusing here is another model 91 schematic that doesn't show parts with dotted lines in that spot, but shows parts with dotted lines in another spot. https://philcoradio.com/library/index.ph...chematics/ . Does your set have a code number?
Getting back to the power cord I suppose you could add a fuse in series with one leg of the power transformer primary, use a fuse block rated for 120 volts, that you can anchor to the chassis, and not an automotive fuse holder. There was a guy on Y.T that used the latter years ago, he used these clunky plastic inline fuse holders with thick pigtails attached, which were never rated for mains voltage, not to mention they looked stupid. If I ever ran into that in a radio it would be clipped out and tossed.
Regards
Arran
I'm pretty sure that the dotted line I circled in an earlier post signifies that it is applicable to the 226 model which has two speakers. Although not annotated in any of the schematics I have found it would be consistent with the code 221 information I have found.
- As far as cleaning the volume pot. I see no hole or spaces in the case to spray any cleaning solution. There may be a small space between the bakelite and metal can sections where the tabs connect.
- A general question regarding the resistors. I've lifted one leg on many of them for measurement and find that they are all near or outside of the 20% tolerance value. Is it common practice to replace all those "dogbone" and fuse-shaped resistors? I see that many of them are listed as .5 watt with a few at 1 watt. If I do replace them I plan on using 1 watt.
- As mentioned earlier this is the oldest radio and only Philco I have ever worked on so I'm learning a lot. A post by MrFixr55 in another topic explains the operation of the multi-tap wirewound resistor. My reading explains that this is not a candohm but operates similarly. The one question I have about this is about the resistance measurements listed in the schematic. Is this reading from the terminal to the ground lug or between it and the nearest terminal?
Usually the dashed lines connected to components means the part is a substitute in the circuit for specific models. You have to be careful when interpreting this because some dashed lines mean something else, as in showing the power switch physical connection to the volume control. They're both controlled by the same shaft.
Yes, cleaning volume controls can be tricky sometimes. There's usually some tiny gap where the terminals enter the case where you can put a spray straw.
When measuring resistors you can leave them in circuit if one end is connected to a tube element other than the filament. Otherwise, you have a good chance of a false reading. The resistor values in the schematic are the values you should measure when out of the circuit. Some schematics will show a voltage chart or tube socket diagram and resistance measurements may also show you the resistance to ground or B-. Resistance readings on a candohm usually show the resistance between lugs, then you have to show your intelligence by adding up the values to find the total of the entire length. Sometimes the parts list will give you the information..
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