The PHILCO Phorum
model 48 464 - Printable Version

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model 48 464 - retired2020 - 11-19-2023

I am having trouble restoring the model 48 464  

I have done the following

recapped
All tubes good 
tested resistance and  voltage readings  as per schematics form John F Ryder publication all good 

I get lots of noise ie static but do not  receive  stations .

Any suggestions ?
Thanks

RE: model 48 464 - morzh - 11-19-2023

Have you performed the alignment procedure?
Do you have a SG?

You need to try to align, and if it does not, see if there is an open RF coil somewhere.
You need to put a signal through, from Antenna to the Speaker.

Noise/static is good. It means your tubes are mostly OK, your power/filters are OK.

RE: model 48 464 - Radioroslyn - 11-19-2023

For those of you following at home here's the info: https://philcoradio.com/library/download/service%20info/yearbooks/1948-1949/split/Part16-Philco%20Home%20Radio%20Yearbook%201948-1949.pdf

I picked up the same set a yr or so ago but it was the am/fm model and it was missing a chunk out of it's side. It was on the table that said FREE and it was 3:00am so I didn't give a good going over. It also came w/a model 84 which was a mouse house but had a good spkr...

RE: model 48 464 - retired2020 - 11-20-2023

Thanks for suggestion 

Yes I have a rf signal generator and it also has an audio generator.
Tried the alignment procedure but could not get any signal after the first step. i then noticed that there are trouble shooting procedures for the radio as per attached. section 1 measuring voltage checked out 
section2 revealed no signal . I checked the resisters since the caps and tubes are good and R203 reads 586 K verses the parts  list of 470 K and R204 read 233K vs 130 ohms Its gets weirder .The next step for section 3 shows  in figure 3 C307 (.05mf) connecting from pin 5 on the 50 A5 to pin 3 on the 7b7  it does not show this on the schemo. the current wiring is pin 2 of the 50 with a .02 mf connected to pin 5 of the 7b7.

I am very carful when replacing caps .I don't remove the old leads from the pin  entirely. I cut the lead from the old cap and connect to that lead so i dont wire to the wrong pin. What  controls the figure 3 or the schemo?  

Also  the rf coils do have continuity and seem ok

RE: model 48 464 - Radioroslyn - 11-20-2023

I'm surprised that if the cathode resistor on the 50a5 measures 233K that you would have any audio at all. Do you have the proper voltages coming from the power supply (110vdc & 92vdc) more or less?

RE: model 48 464 - retired2020 - 11-20-2023

yes the voltages are correct When i tested for them I used a Variac to ensure the the line voltage was 117 volts as per the testing protocol .

RE: model 48 464 - Radioroslyn - 11-21-2023

Ok so if you measure the dc voltage from the cathode of the 50A5 (+) and B- to the negative meter lead. Should see about 6vdc there if the resistor is 130 ohms. If it's 233K it's going to be a whole lot more like 30 or 40v. This will cause the tube not to conduct. Replace w/a 1 or 2 w replacement.

RE: model 48 464 - retired2020 - 11-26-2023

I rechecked the BC & Sw oscillator more carefully with a magnifying glass. Sure enough one of the  hair thin wires to one of the  posts was disconnected I reconnected and now get two to three AM stations which isn't too bad since i am in a basement with no exterior antenna. Additionally  i checked R203 ,650 k vs 470 k on schemo R204 was 257vs 130 on schemo . I replaced both and reception is much better . Still trying to realign but cant get alignment signals to the radio. 

You have been tremendously helpful  to this newbie !