02-04-2026, 11:58 PM
Hi Gpurtchick,
I think that you definitely on the right track! Having the metal shields of the tubes floating is just asking for interference.
Re the oscillator tracking, I think that you should try adjusting trimmers 4A and 4B as well as C7 and C9 to try to get the 470KHZ spread that you are looking for.
As far as tuning the IF to 440KHz, the only issue is if the transformers are as efficient at 440 KHz as they are at 470 KHz. If the radio performs well at an IF of 440 KHz and you can't get the RF- Osc difference to 470 KHz, then go with what's easy.
I assume that by "WOW", you meant that you received a plethora of channels when you touched the grid cap. So yes, there may be a short and likely in the primary of the coil If the secondary was shorted, then this would greatly affect the tuned circuit. I suppose that you can just cheat and run the antenna wire to the 6A8 grid cap.
An alternative would be to use a loop or ferrite loopstick, instead of the antenna coil, thereby eliminating the need for an external antenna. Loopsticks are directional so mount away from the chassis in such a manner as to maximize the signal with the radio in the direction that you desire. In addition, you would have to figure a way to put it in place of only the Broadcast Band section of the coil assembly if you want to use the Shortwave.
Congratulations on your progress!!
I think that you definitely on the right track! Having the metal shields of the tubes floating is just asking for interference.
Re the oscillator tracking, I think that you should try adjusting trimmers 4A and 4B as well as C7 and C9 to try to get the 470KHZ spread that you are looking for.
As far as tuning the IF to 440KHz, the only issue is if the transformers are as efficient at 440 KHz as they are at 470 KHz. If the radio performs well at an IF of 440 KHz and you can't get the RF- Osc difference to 470 KHz, then go with what's easy.
I assume that by "WOW", you meant that you received a plethora of channels when you touched the grid cap. So yes, there may be a short and likely in the primary of the coil If the secondary was shorted, then this would greatly affect the tuned circuit. I suppose that you can just cheat and run the antenna wire to the 6A8 grid cap.
An alternative would be to use a loop or ferrite loopstick, instead of the antenna coil, thereby eliminating the need for an external antenna. Loopsticks are directional so mount away from the chassis in such a manner as to maximize the signal with the radio in the direction that you desire. In addition, you would have to figure a way to put it in place of only the Broadcast Band section of the coil assembly if you want to use the Shortwave.
Congratulations on your progress!!
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
"Let us begin to do good"- St. Francis
Best Regards,
MrFixr55




