03-19-2022, 08:22 AM
Hi Tgr131,
First off, It looks like your enthusiast friend did rather nice work. I like the coil on the end of the new cap. Looks like it would act as a "socket", holding it in place. This technique would minimize heating existing joints.
Your technique would work. In fact, my RCA 14BT1 battery "farm" Set (1.5 / 90V Batteries) had the phono jack installed by RCA in the exact manner.
Better fidelity can be obtained by breaking into the audio circuit by installing a SPDT switch as follows:
Break the connection between C38 (the input to the Audio Amp) and the junction between R39 and R37D (the output of the Detector). Connect the common pole of the SPDT Switch to C38. Connect one switchable leg to the junction of R37D and R39. Connect the other leg to the Audio Jack that you are using. Use shielded cable if necessary but ground the shielded cable between the switch, detector output and audio amp input at only 1 point to prevent ground loops. If the audio jack is not grounded to the chassis, connect the ground terminal to the shielded cable and ground at the other end of the shield. I will try to attach drawings.
Many Radios of this vintage had this feature as several manufacturers (RCA in particular) offered "Phono Adaptors" for radios. These Phonos had no Audio Amplifiers, as the Radio was to be used for this. The proposed TV sets between 1939 and the end of consumer electronic production due to WWII also used the radio as an audio amplifier. RCA sold a kit (Type 240X1)to add the above switch to the back of the cabinet. All of this legitimizes this modification, assuming this is done with period parts.
My Philco 41-255 did something different. they advertised "FM and TV sound the Wireless Way" Ther is a pushbutton on the presets for "TV FM Phono" I do not know the frequencies used, but each of these required a built in "Wireless Oscillator".
Direct connection always produces better sound than using a transmitter, no matter how good the transmitter is.
Best Regards,
John, MrFixr55
First off, It looks like your enthusiast friend did rather nice work. I like the coil on the end of the new cap. Looks like it would act as a "socket", holding it in place. This technique would minimize heating existing joints.
Your technique would work. In fact, my RCA 14BT1 battery "farm" Set (1.5 / 90V Batteries) had the phono jack installed by RCA in the exact manner.
Better fidelity can be obtained by breaking into the audio circuit by installing a SPDT switch as follows:
Break the connection between C38 (the input to the Audio Amp) and the junction between R39 and R37D (the output of the Detector). Connect the common pole of the SPDT Switch to C38. Connect one switchable leg to the junction of R37D and R39. Connect the other leg to the Audio Jack that you are using. Use shielded cable if necessary but ground the shielded cable between the switch, detector output and audio amp input at only 1 point to prevent ground loops. If the audio jack is not grounded to the chassis, connect the ground terminal to the shielded cable and ground at the other end of the shield. I will try to attach drawings.
Many Radios of this vintage had this feature as several manufacturers (RCA in particular) offered "Phono Adaptors" for radios. These Phonos had no Audio Amplifiers, as the Radio was to be used for this. The proposed TV sets between 1939 and the end of consumer electronic production due to WWII also used the radio as an audio amplifier. RCA sold a kit (Type 240X1)to add the above switch to the back of the cabinet. All of this legitimizes this modification, assuming this is done with period parts.
My Philco 41-255 did something different. they advertised "FM and TV sound the Wireless Way" Ther is a pushbutton on the presets for "TV FM Phono" I do not know the frequencies used, but each of these required a built in "Wireless Oscillator".
Direct connection always produces better sound than using a transmitter, no matter how good the transmitter is.
Best Regards,
John, MrFixr55
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
Best Regards,
MrFixr55
