Hi,
I am still a beginner even if I did now 5 radios after my first post and the last one before this was a very beautiful 37-620.Thanks to this forum I learned many things but not enough.
I bought now a beautiful 48-1264 Radio with recorder and collected all the schematics from Philco year book 1948-1949 and I was ready to start the recap of the section 1 but I am not able to find the resistor Bias R100 165 ohms.The radio was without the speaker and I think someone already started to look inside or to sell some components like the speaker. No new components are installed yet.
I am not sure if something is missing ( the resistor) or someone changed the schematic connections? I attached some pictures from section 1.
In case the Resistor is really missing what I can use to replace it? Do you know how many watts it is?
I found the R101 from the code that is a 2 Watts is the R100 the same?
Thank you so much
Camillo
The resistor in the middle of the 1st pic that looks like a shoe lace w/metal ends will be the one that developes the - bias. They are called flexible resistors but don't bend it as it is probably brittle by now and the nichrome wire inside will break.
Hi Terry,
thank you so much I thought it was only a wire.......many things to learn. It is 174 ohms instead of 165 is it ok for a first testing or I need to change it?
Following the schematic that is really with a low quality (Nostalgia org or Philco year 1948 book have same quality) I also found something that is not clear to me in the section 1.
The C102 20uF +B , the resistor R101 and the speaker field are connected on the radio to pin 2 of the rectifier 5AZ4, but in the schematic they go to pin 8. The two blue wires from T100 go to pin 2 and pin 8. What is correct the schematic or the cabling I have on the radio?
When I will understand and identified all the components and the connection on the schematic I will start the recap and testing of the voltages
Thank you so much for your support
Camillo
https://philcoradio.com/library/download...8-1949.pdf
> It is 174 ohms instead of 165 is it ok for a first testing or I need to change it?
Nah your <10%.
>What is correct the schematic or the cabling I have on the radio?
Pins 2 and 8 are at the same + positive in regards to the chassis ground. Do not short the two pins together as there is 5v@2a across them. Using pin 2 or 8 as a high volt point is fine so either wiring is ok as per the schematic.
Hi ,
during a long time search on ebay for the Field coil missing in the Radio that now I installed , I recapped all the radio and found 3 bad Resistor and changed them. At the first switch on verifying the voltages I discovered the lost of voltage (240V) on pin 2 of the 7R7 tube.
Checking the Z302 I discovered no continuity between the blue and the red wire.
I opened the IF and I found 3 ohms instead of the 13 ohms between the blue wire and the firs coil. No continuity between the red wire and the connection between the two coils.( the 10 ohms coil)
I started to unwire the coil and unfortunately it was burned and interrupted at the end of the coil and after many turns the wire must be changed.
I have some questions now.
Because I have 3 ohms between the blue wire and the first connection of the coil this means that also the first coil has some problems? It will be challenge rewinding it has a connection with the C302 capacitor in the middle of the coil....
I was not sure about the position of the coil after the Wax cleaning I checked all the other coils on Z302 . They have continuity and the right ohms.
The coil I unwired is the first thin with many turns 4 parallels and all the other on top. Is it the right one? Because after the fiftieth turn I lost the count what is the right number of turns? What kind of wire I need to buy to rewind the coil?.
I attached a Photo the coil open is the first ring on the bottom near the soldering connector
Thanks
Camillo
Unfortunately the questions you ask there are no documented answer to. The # of turn size of wire ect are all unknowns. Looks like you need to find another transformer or parts chassis. I'd look at some of the other '47-'49 set for the same type of circuit.
GL
Hi Terry,
Thank you so much.
I found that the 47-1230 has the same part number even if in the schematic there are some differences.I am not sure about other models
Any suggestion where I can search it?
Rewinding it is a mission impossible without knowing the number of the turns but only the resistance and the gauge of the wire ( not yet verified)?
Thanks
CAmillo
Hi,
I tried to find the spare Philco 32-4147( IF Coil of Philco 48-1264) but I don't think It will be simple.
I also red some articles on the coils and discovered that for a beginner it can be a possible work to rewind an RF Coil, but when you find an open IF coil if the open part is the Inductor one it is almost impossible. From other posts I learned that in most of the cases ( like mine) they are open at the real beginning and when you unwind it is complex maintain the overall integrity. Second I learned that the wire is in the reality a wire twisted on another core to form and Inductor I suppose?
In this moment due to the open wire I don't have the 240V on the pin 2 of the 7R7 tube ( blue wire IF z302)
On these facts if I will not find a spare can I make some kind of bypass?
Thanks to the great support from this great forum
Camillo
So which primary coil is open top one, bottom one, or both?
Hi,
Sorry I was wrong in the previously post .The bottom one in the pictures I attached before. On the schematic it is open the lower one ( 10 Ohms) with the red wire and the mica capacitor in parallel. The first one in the schematic has a lower resistance 3 ohms instead of 13 ( the one with the blue wire).
Another wrong point I wrote is the voltage on pin 2 of the 7R7 is ok with 240V . I don't have voltage on the other end of the red wire on the pin 6 of the 6K6GT
Thanks
Camillo
Ok you have kinda lost me. Do you have hv on the red wire??
No I don’t have voltage at all on the red wire.
From the continuity point of view it is open between the blue wire and the red of the if z302. opening the can there is continuity between the blue wire and the first section but it is open from the second section and the red wire
Camillo
Ok so we need to find why there isn't hv on the red wire. Check R-314 (open) or C-322 (shorted). Not sure what's going on at pin 6 on the 6K6. It's not showing any connection and there is no internal connection in the tube. It's used as a tie point for something.
Hi Terry,
thank you so much. They are ok I verified them with the meter. The Pin 6 of 6K6Gt is used to connect together the red wire of the IF Z302 with one leg of the C322 and one leg of the R314. I checked the voltage on this point and there is not Voltage at all. The second leg of the C322 goes to the ground and the second leg of the R314. goes to pin 4 of 6K6GT.
This is the reason I checked with the ohms between the red wire and the blue wire of the IF 302 and it was open. I supposed there was an open coil and opened the IF.
You can see the other parts of the post where I described what I did. I tried to find the open coil inside the IF Z302 between the blue wire and the red wire and discovered that the first section from the blue wire and the end of the 13 ohm coil was 3 ohms instead of 13, but the section of the second 10 ohms coil and the red wire was open.
This is the reason why I tried to find the open wire and now I have to rebuild it
Thanks for any suggestion
Camillo
Ok so it would seem to me that you need to measure the resistance or r-314. It's either very high or open... Once that is sorted you should have hv on the red wire. OBTW one side should have hv on it now (pin 4) and the red wire side doesn't. This also assumes that pin 4 of the 6K6 has hv on too, it should and pin 3 on both 6K6's.
There is some good news coming...