02-02-2026, 04:35 PM
Hi Wallace,
No reason to be ashamed of being risk adverse, as some of these parts are hard to replace. Risk adversity is less exciting than taking risks but it is also way less expensive.
Refer to the schematic of the audio section that I previously posted. Yes, the 2 wires with a 500 Ohm reading between them go to the 2 bottom pins. Order should not important. Yes, between the other 2 wires should be 3100 Ohms.
But the order of those 2 wires IS important. Measure resistance between one of the 2 wires to the 71A plates and each of the other 2 wires that go to the field coil. One of those 2 wires goes to both the field coil and the center tap of the output transformer. Resistance between that wire and either of the 2 leads to the plates of the 71As is roughly 250 ohms, depending on which plate lead you are measuring to. It is normal that the readings between this wire and each of the 2 plate leads are not the same. This is lead D and goes to the upper right of the socket (viewed from the outside. It is supplied by the power supply and delivers power to the field coil and the output transformer.
The other lead will measure approximately 3350 Ohms when measured against one of the plate leads. This is Lead J which supplies a lower B+ voltage from the field coil to other parts of the radio.
I don't think that you would smoke anything. However, reversing the wires would greatly lower the B+ voltage to the output stage and sound level and fidelity would be greatly affected.
No reason to be ashamed of being risk adverse, as some of these parts are hard to replace. Risk adversity is less exciting than taking risks but it is also way less expensive.
Refer to the schematic of the audio section that I previously posted. Yes, the 2 wires with a 500 Ohm reading between them go to the 2 bottom pins. Order should not important. Yes, between the other 2 wires should be 3100 Ohms.
But the order of those 2 wires IS important. Measure resistance between one of the 2 wires to the 71A plates and each of the other 2 wires that go to the field coil. One of those 2 wires goes to both the field coil and the center tap of the output transformer. Resistance between that wire and either of the 2 leads to the plates of the 71As is roughly 250 ohms, depending on which plate lead you are measuring to. It is normal that the readings between this wire and each of the 2 plate leads are not the same. This is lead D and goes to the upper right of the socket (viewed from the outside. It is supplied by the power supply and delivers power to the field coil and the output transformer.
The other lead will measure approximately 3350 Ohms when measured against one of the plate leads. This is Lead J which supplies a lower B+ voltage from the field coil to other parts of the radio.
I don't think that you would smoke anything. However, reversing the wires would greatly lower the B+ voltage to the output stage and sound level and fidelity would be greatly affected.
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
"Let us begin to do good"- St. Francis
Best Regards,
MrFixr55




