Hello All,
I it looks like just one diode used for FM detection in this radio. How is this done? Maybe I'm wrong, but that's what it looks like:

http://techpreservation.dyndns.org/schematics/49/49_Philco_48-472_1-87.djvu

I cannot find this schematic here. Is this also known as another model?

Thanks,

Dave

Hello Again,
The FM and AM detector tube in this radio is a 14X7. Also, I don't understand why spaces I have typed disappear. I typed "is used" and it got sent as "isused". I don't remember typing "I" at the beginning of the first sentence, but there it is. Sorry about that.

Dave
:Hello All,
: I it looks like just one diode used for FM detection in this radio. How is this done? Maybe I'm wrong, but that's what it looks like:
:
:http://techpreservation.dyndns.org/schematics/49/49_Philco_48-472_1-87.djvu
:
:I cannot find this schematic here. Is this also known as another model?
:
:Thanks,
:
:Dave
:

Edd,
I don't have this set in front of me. But I'll check that when I see it. I was just wondering about the method of FM detection. It's a standard ratio detector. Nothing unusual.

Thanks very much,

Dave
:
:

: : : : : : : : : : :Sir Dave . . . . . . : : :The set is using a ratio deee-tector . . . the 14X7 being your 6T8'ish loktal equivalency. : : :the particular page that they show is giving the AM detection path with its heavy highlighting. : : :Albeit, a little hard to differentiate, with the copys quality of definition and digital "trash" that it has taken on in compression. : : :You can see the AM signal from the top of the AM I.F. output winding on the bottom right quadrant of Z302 is flowing on up off the high side and passing thru FM tertiary winding (12 ohms)and then into the top half (1ohm) of the FM secondary winding and then out the top over to the pin 5 plate of the 14X7 for AM detection. : : :The AM developed audio is taken off the bottom of the initially mentioned right bottom quadrants 11 ohm winding and DOWN the heavy black path to then branch off to the right to feed the vol-you-me control high side terminal . : : : :In the FM operative aspect the FM signal on the Z302 top portion is taking an RF phasing sample :via C302B and then the secondary of the FM det transformer is having the opposite ends of the secondary winding, each being sent to a detector element. : : :One winding end goes to the plate /anode at pin 5 of the 'X7 and the other winding end is routed to a cathode at pin 7. :The FM detection processing is then comparing the relationship between the static C302B sample and the induced signals of the secondary winding. : : :The FM detected signal is taken off the centertap of the FM det secondary winding and then thru the tertiatry (12 ohms) winding and then down thru the 11 ohm winding of the secondary of the AM transformer of the Z302 pair and then into the volume control function. : : :The pin 6 diode of the 'x7 is used as a DAVC function in the AM mode. : : : :Thassit. . . . . . : : :No pick-churs being required . . . . : : : : :Pee Ess . . . be sure C319 . . . 5ufd electrolytic . . . hasn't dried out on you, affecting the FM mode. : : : : :73's de Edd : : : :

:
:
:
:
:FONT SIZE=4 FACE="Comic Sans MS"COLOR=00C000>
:
:
:
::Hello Again,
:: The FM and AM detector tube in this radio is a 14X7. Also, I don't understand why spaces I have typed disappear. I typed "is used" and it got sent as "isused". I don't remember typing "I" at the beginning of the first sentence, but there it is. Sorry about that.
::
::Dave
:::Hello All,
::: I it looks like just one diode used for FM detection in this radio. How is this done? Maybe I'm wrong, but that's what it looks like:
:::
:::http://techpreservation.dyndns.org/schematics/49/49_Philco_48-472_1-87.djvu
:::
:::I cannot find this schematic here. Is this also known as another model?
:::
:::Thanks,
:::
:::Dave
:
:FONT SIZE=4 FACE="Comic Sans MS"COLOR=000000>
:::
::
:

Edd,
I just replaced the, what I thought were all the paper and electrolytic capacitors in this circuit. Thanks for reminding me about C319, discriminator "filter" capacitor. Right now I have no FM.

Thanks Again,

Dave
:
:

: : : : : : : : : : :Sir Dave . . . . . . : : :The set is using a ratio deee-tector . . . the 14X7 being your 6T8'ish loktal equivalency. : : :the particular page that they show is giving the AM detection path with its heavy highlighting. : : :Albeit, a little hard to differentiate, with the copys quality of definition and digital "trash" that it has taken on in compression. : : :You can see the AM signal from the top of the AM I.F. output winding on the bottom right quadrant of Z302 is flowing on up off the high side and passing thru FM tertiary winding (12 ohms)and then into the top half (1ohm) of the FM secondary winding and then out the top over to the pin 5 plate of the 14X7 for AM detection. : : :The AM developed audio is taken off the bottom of the initially mentioned right bottom quadrants 11 ohm winding and DOWN the heavy black path to then branch off to the right to feed the vol-you-me control high side terminal . : : : :In the FM operative aspect the FM signal on the Z302 top portion is taking an RF phasing sample :via C302B and then the secondary of the FM det transformer is having the opposite ends of the secondary winding, each being sent to a detector element. : : :One winding end goes to the plate /anode at pin 5 of the 'X7 and the other winding end is routed to a cathode at pin 7. :The FM detection processing is then comparing the relationship between the static C302B sample and the induced signals of the secondary winding. : : :The FM detected signal is taken off the centertap of the FM det secondary winding and then thru the tertiatry (12 ohms) winding and then down thru the 11 ohm winding of the secondary of the AM transformer of the Z302 pair and then into the volume control function. : : :The pin 6 diode of the 'x7 is used as a DAVC function in the AM mode. : : : :Thassit. . . . . . : : :No pick-churs being required . . . . : : : : :Pee Ess . . . be sure C319 . . . 5ufd electrolytic . . . hasn't dried out on you, affecting the FM mode. : : : : :73's de Edd : : : :

:
:
:
:
:FONT SIZE=4 FACE="Comic Sans MS"COLOR=00C000>
:
:
:
::Hello Again,
:: The FM and AM detector tube in this radio is a 14X7. Also, I don't understand why spaces I have typed disappear. I typed "is used" and it got sent as "isused". I don't remember typing "I" at the beginning of the first sentence, but there it is. Sorry about that.
::
::Dave
:::Hello All,
::: I it looks like just one diode used for FM detection in this radio. How is this done? Maybe I'm wrong, but that's what it looks like:
:::
:::http://techpreservation.dyndns.org/schematics/49/49_Philco_48-472_1-87.djvu
:::
:::I cannot find this schematic here. Is this also known as another model?
:::
:::Thanks,
:::
:::Dave
:
:FONT SIZE=4 FACE="Comic Sans MS"COLOR=000000>
:::
::
:

Hi Dave,

Check your email for a pdf schematic.

Looks like a ratio detector, (2 diodes).

Gary

:Hello All,
: I it looks like just one diode used for FM detection in this radio. How is this done? Maybe I'm wrong, but that's what it looks like:
:
:http://techpreservation.dyndns.org/schematics/49/49_Philco_48-472_1-87.djvu
:
:I cannot find this schematic here. Is this also known as another model?
:
:Thanks,
:
:Dave
:

Gary,
OK. Two diodes for the ratio detector. What about the diode for the AM detector. Where's that, or is one diode shared?
The schematic is very good. Much better than the djvu version on-line.

Thanks,

Dave
:Hi Dave,
:
:Check your email for a pdf schematic.
:
:Looks like a ratio detector, (2 diodes).
:
:Gary
:
::Hello All,
:: I it looks like just one diode used for FM detection in this radio. How is this done? Maybe I'm wrong, but that's what it looks like:
::
::http://techpreservation.dyndns.org/schematics/49/49_Philco_48-472_1-87.djvu
::
::I cannot find this schematic here. Is this also known as another model?
::
::Thanks,
::
::Dave
::
: