Philco 43 - Filter Choke - Printable Version
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Philco 43 - Filter Choke - Masonparker - 02-13-2021
The filter choke in the radio is shot. The original choke had an inductance of 100H and a resistance of 2100 ohms. I ordered a replacement choke from Radio Daze part 154E which is 20H at 1666 ohms
First question - looking at the Philco Book - Condensers and More it tells me if I replace the filter choke with an lower inductance I need to increase the associated filter capacitor. Based the attached schematic I think this would be item 47. But how much should I increase the Electrolytic condenser right now i have a 1 8mf.
Second question - I read another post where it said you could replace the choke with a two watt 2100 ohm resistor and also increase the mf's of the condenser. So if i used this method again would this be item 47 and what mf should I use
RE: Philco 43 - Filter Choke - Radioroslyn - 02-13-2021
I wouldn't use a resistor for a rf filter.
A choke will do a much better job. For now I'd leave 47 @ 8mf see what happens depending on what it's trying to do. It's either stopping noise from other circuits from getting into the osc or signals from the osc getting out of the osc. Common practice now days would be to use a small value cap across 47 like a .01 or .005. This most of the time will block the signals from getting out. The choke and large cap stops low frequency (audio,hum, and such) from getting in.
When you get it working and it doesn't want to settle down squealing and behaving badly add some more mfd's there.
RE: Philco 43 - Filter Choke - morzh - 02-13-2021
The capacitor should increase proportionally to the decreasing capacitance. This said, you probably will be OK with 20H, but you do need to increase the resistance a bit so adding 400 Ohm resistor in series with the choke will keep the DC voltages the same way they were intended to be. I would increase the capacitance. I am sure it will work with 8uF, but it is easy to put in 47uF instead so why not.
RE: Philco 43 - Filter Choke - Masonparker - 02-21-2021
The new choke came in added the resistor to get to the 2100 ohm changed the two condensers to 30 mfd (didn't have a 47). Powered up the radio and the hum is gone but no sound. So I started to check voltages. The voltage at the rectifier checked out - F-F was 4.65V and voltage at each plates were 349V and 347V . I check the voltage across the center tap and it was reading 350V on each side. All the filament voltage at all the tubes were good. But I have no voltage at any of the plates. Any thoughts what i should try next???
RE: Philco 43 - Filter Choke - Radioroslyn - 02-21-2021
Is the spkr plugged in? What dc voltage do you have from the 80 filament to the chassis?
RE: Philco 43 - Filter Choke - morzh - 02-21-2021
>>powered up the radio and the hum is gone but no sound
I assume when someone says "no sound" he has the speaker plugged in, else it would not create the question "why"
Just trace the B+ along the way.
See where it stops.
RE: Philco 43 - Filter Choke - Masonparker - 02-22-2021
Speaker was plugged in so that was easy. Found a loose wire and start to get B voltage readings. I attached the readings up to the 1st Det (tube 44) . Then a new problem the wire resistor (item 57) part # 6450 started to heat up and smoke. Unplugged and called it a night. So can you look at the attached reading a let me know what you think and what should a do with the wire resistor. Having a hard time giving up on this the cabinet restoration came out perfect just need the radio now
RE: Philco 43 - Filter Choke - morzh - 02-22-2021
57 smoking, you have a general overload somewhere, as this is the Negative to Chassis: almost all current goes through it.
Check 1st AF for short, socket and all.
Have you checked your tubes?
RE: Philco 43 - Filter Choke - Masonparker - 02-22-2021
What is 57 smoking?? Any advice where to start looking? Could I have shorted out a tube while testing the voltage? The reason I ask is that the smoking started when I was testing the voltage at the grid cap
RE: Philco 43 - Filter Choke - Masonparker - 02-22-2021
I did check all the tube with the tube tester they came up good, but with that yes the tube tester is 80 years old
RE: Philco 43 - Filter Choke - Masonparker - 02-22-2021
I check the 1st audio and found the K terminal was grounded to the chassis ( it was pitched under the bakelite condenser) While tracing this I found the 13,000 ohm resistor (item 60) should be a 3 watt resistor only had a 1/2 watt - So I will replace this when i order a 3 watt highest i have on hand is two watts
RE: Philco 43 - Filter Choke - morzh - 02-22-2021
If the 1st AF K is grounded the 57 should not smoke; in fact there will be no current through it, so whatever it was that made it smoke it was not it.
RE: Philco 43 - Filter Choke - Masonparker - 02-23-2021
Could have the resistor failed and is shorting to ground Only the 245 ohm side was smoking and is still reading good at 246.3
RE: Philco 43 - Filter Choke - Radioroslyn - 02-23-2021
The 185 and 245 ohm resistor are grounded at one end so if you ground the other it relieves any current flow thru it. So no wouldn't cause it to burn up. I would have a look around the 1st audio stage 39/44 tube as the cathode and screen voltage are developed at that string of resistors. Try removing the tube and see if you get the same results. Check for something that maybe shorting the socket at the screen or plate pins. Use an ohm meter to chassis ground. At the plate or screen should see something around 5k-10k and not 5-10 ohms.
RE: Philco 43 - Filter Choke - Masonparker - 03-18-2021
I replaced the 3W resistor and that fix the overheating of item 57 and no more smoking. Radio powers up fine very low hum, slight static as i go up and down the dial but that is it .