12-27-2023, 07:59 PM
Thanks for update,
It is the buffer condenser that has to have a pulse rating Part #60, 7500 pf, the OEM may be paper or mica but it is of foil electrodes, the foil can easily take the kickback pulses of the power transformer, metalized capacitor in this service cannot and in time metalizing separates and looses capacity. If the required value cannot be found two of double the value in series are fine. For example two .015 at 630 Cornell or equivalent: 0.0150 mf WPP6S15K–F. If a single cap at .0075mf can be found do go to 1kv or more. Deviating more than 10% from the MF value risks shortening the life of the mechanical vibrator as far an an electronic vibrator, dunno?
The radio uses a electrodynamic speaker, that field coil uses about an amp by itself, it is possible to replace with a PM speaker as the field is not part of any voltage drop or power filtering.
The +6 volts will be via a #10 wire from the auto ACC terminals, the ground or return is the chassis, sometimes assisted with a #2 braid from the radio chassis to the firewall. There should be a much heavier braid from the chassis to the frame/battery as the body is or was rubber isolated. The heavy cabling is to reduce voltage drop to the supply for the radio, reduce the impedance at RF and allow for the heavy current surge when turning on the radio.
There is no indication of the type of antenna wire used. I suspect it is the very low capacity type that is basically a braid over a hollow tube and a 24ga copperweld center conductor "flopping around" inside.
Modern coax is around 22 pf per foot, no matter if it is terminated at its characteristic impedance but in the auto that capacitance may put it out of resonance so the signal will be marginalized. If a replica FORD antenna assembly for that model type/year is available, that, should work fine... Try 50 ohm coax it the antenna trimmer can peak properly and radio is sensitive across the band then fine...
This a quality Philco radio, with a fully tuned RF stage. Its sensitivity should be awesome on the bench and in the vehicle...
Caps #41 and #42 could also benefit from a dv/dt rated type, static crashes cut off the OPT and the collapsing magnetic field can puncture OPT windings. Same static pulse can degrade common metalized caps.
Oldest auto radio I rebuilt was a 40 Ford for a friend now SK. He had to find replica plastic indicators for the dial...
Oh, last word, any new part that may be on long leads, tag down to chassis with blob of electrical silicone. Auto vibration can work harden component leads until they break off...
GL
Chas
It is the buffer condenser that has to have a pulse rating Part #60, 7500 pf, the OEM may be paper or mica but it is of foil electrodes, the foil can easily take the kickback pulses of the power transformer, metalized capacitor in this service cannot and in time metalizing separates and looses capacity. If the required value cannot be found two of double the value in series are fine. For example two .015 at 630 Cornell or equivalent: 0.0150 mf WPP6S15K–F. If a single cap at .0075mf can be found do go to 1kv or more. Deviating more than 10% from the MF value risks shortening the life of the mechanical vibrator as far an an electronic vibrator, dunno?
The radio uses a electrodynamic speaker, that field coil uses about an amp by itself, it is possible to replace with a PM speaker as the field is not part of any voltage drop or power filtering.
The +6 volts will be via a #10 wire from the auto ACC terminals, the ground or return is the chassis, sometimes assisted with a #2 braid from the radio chassis to the firewall. There should be a much heavier braid from the chassis to the frame/battery as the body is or was rubber isolated. The heavy cabling is to reduce voltage drop to the supply for the radio, reduce the impedance at RF and allow for the heavy current surge when turning on the radio.
There is no indication of the type of antenna wire used. I suspect it is the very low capacity type that is basically a braid over a hollow tube and a 24ga copperweld center conductor "flopping around" inside.
Modern coax is around 22 pf per foot, no matter if it is terminated at its characteristic impedance but in the auto that capacitance may put it out of resonance so the signal will be marginalized. If a replica FORD antenna assembly for that model type/year is available, that, should work fine... Try 50 ohm coax it the antenna trimmer can peak properly and radio is sensitive across the band then fine...
This a quality Philco radio, with a fully tuned RF stage. Its sensitivity should be awesome on the bench and in the vehicle...
Caps #41 and #42 could also benefit from a dv/dt rated type, static crashes cut off the OPT and the collapsing magnetic field can puncture OPT windings. Same static pulse can degrade common metalized caps.
Oldest auto radio I rebuilt was a 40 Ford for a friend now SK. He had to find replica plastic indicators for the dial...
Oh, last word, any new part that may be on long leads, tag down to chassis with blob of electrical silicone. Auto vibration can work harden component leads until they break off...
GL
Chas
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”
