06-16-2024, 11:42 AM
I know I asked about the speaker...
But I will again.
The plate current (B+-135) for the LAST AUDIO tube must flow through the speaker coils or some sort of audio coupler in the speaker. So measure the DC resistance using a analog meter. must be something less than 2K and more than 500 ohms. A cone speaker will not have polarity to be concerned with. Side note the last audio only gets the -22-1/2 volts "C"
A diaphragm speaker will have polarity, it should be connected such that plate current draws the diaphragm inward. That, action re-enforces the internal magnet and makes the speaker more sensitive. Long term in the incorrect polarity will weaken the internal magnet. The panel jacks can be problematic, be sure they are clean and that no wire strands are shorting at the terminals.
Bias to the RF tube "flows" through the loop, the connections must be clean, teasing the blade connections on the bottom of the loop and in the loop socket will help. If the signals are "scratchy" when the loop is turned the connections are not secure.
If you get regeneration oscillation the loop trimmer must be adjusted. Follow the RCA instructions. If that clears it up, great. If not then there is a poor connection somewhere.
Good Luck!
Chas
But I will again.
The plate current (B+-135) for the LAST AUDIO tube must flow through the speaker coils or some sort of audio coupler in the speaker. So measure the DC resistance using a analog meter. must be something less than 2K and more than 500 ohms. A cone speaker will not have polarity to be concerned with. Side note the last audio only gets the -22-1/2 volts "C"
A diaphragm speaker will have polarity, it should be connected such that plate current draws the diaphragm inward. That, action re-enforces the internal magnet and makes the speaker more sensitive. Long term in the incorrect polarity will weaken the internal magnet. The panel jacks can be problematic, be sure they are clean and that no wire strands are shorting at the terminals.
Bias to the RF tube "flows" through the loop, the connections must be clean, teasing the blade connections on the bottom of the loop and in the loop socket will help. If the signals are "scratchy" when the loop is turned the connections are not secure.
If you get regeneration oscillation the loop trimmer must be adjusted. Follow the RCA instructions. If that clears it up, great. If not then there is a poor connection somewhere.
Good Luck!
Chas
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
