09-29-2025, 01:00 AM
Hi Dave,
Yeah, I would definitely call that grounded.
Reviewing your pictures. You will see 2 Bakelite capacitor "blocks". The one only partially in view is Cap # 19 which couples the detector plate to the 1st AF grid and should be 0.01 uF. The one more totally in view is Cap # 11 which is a B+ bypass cap for the 1st audio, detector and RF amps and should be 0.05 uF. It is important that the caps in these blocks be changed. There are 2 ways of doing so. One way is to pass a drill through the rivets for the terminals for these blocks to sever the connections to the capacitors within before "bridging" the connections to the block with new caps. The other way is to remove the contents of the block and replace these contents with new caps. Below is a link on how to remove the innards of these blocks without desoldering the leads.
https://philcoradio.com/library/index.ph...soldering/
Another thing to check are the values of the resistors, which so often change values by much more than the 10-20% acceptable tolerance limits. Resistors #12 and #18 are 100KOhms. Resistors #17 and #20 are 500KOhms. Resistor #20, shown in the picture as the grey resistor with the red, yellow and white bands, is the 1t AF amp grid leak resistor. It is a good idea to change Resistor #20. Changing Caps # 19 and #12 are mandatory.
Resistor #17, combined with Resistor #18 provide B+ to the detector. 100KOhm resistor #12, shown in the picture as the white and orange "dog bone" resistor provides cathode bias to the detector. If any of these resistors or the 250KOhm screen grid resistor, #15 are sufficiently out of tolerance, the detector will not work.
The Nostalgia Air schematic for this set lists various voltages. the voltages for the detector will be much different when measured with a modern DVM, FET VOM or VTVM.
In a previous post, I explained the volume control. It does 2 things. It shunts the antenna, limiting the signal input when lowered, and increases cathode bias as lowered by increasing the cathode voltage. Remember that this set does not have AVC. Turning the volume control full clockwise may cause saturation of the RF amps. the section that adjusts the cathode bias is part of the "voltage divider" resistance "chain".
Hope this helps.
Yeah, I would definitely call that grounded.
Reviewing your pictures. You will see 2 Bakelite capacitor "blocks". The one only partially in view is Cap # 19 which couples the detector plate to the 1st AF grid and should be 0.01 uF. The one more totally in view is Cap # 11 which is a B+ bypass cap for the 1st audio, detector and RF amps and should be 0.05 uF. It is important that the caps in these blocks be changed. There are 2 ways of doing so. One way is to pass a drill through the rivets for the terminals for these blocks to sever the connections to the capacitors within before "bridging" the connections to the block with new caps. The other way is to remove the contents of the block and replace these contents with new caps. Below is a link on how to remove the innards of these blocks without desoldering the leads.
https://philcoradio.com/library/index.ph...soldering/
Another thing to check are the values of the resistors, which so often change values by much more than the 10-20% acceptable tolerance limits. Resistors #12 and #18 are 100KOhms. Resistors #17 and #20 are 500KOhms. Resistor #20, shown in the picture as the grey resistor with the red, yellow and white bands, is the 1t AF amp grid leak resistor. It is a good idea to change Resistor #20. Changing Caps # 19 and #12 are mandatory.
Resistor #17, combined with Resistor #18 provide B+ to the detector. 100KOhm resistor #12, shown in the picture as the white and orange "dog bone" resistor provides cathode bias to the detector. If any of these resistors or the 250KOhm screen grid resistor, #15 are sufficiently out of tolerance, the detector will not work.
The Nostalgia Air schematic for this set lists various voltages. the voltages for the detector will be much different when measured with a modern DVM, FET VOM or VTVM.
In a previous post, I explained the volume control. It does 2 things. It shunts the antenna, limiting the signal input when lowered, and increases cathode bias as lowered by increasing the cathode voltage. Remember that this set does not have AVC. Turning the volume control full clockwise may cause saturation of the RF amps. the section that adjusts the cathode bias is part of the "voltage divider" resistance "chain".
Hope this helps.
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
"Let us begin to do good"- St. Francis
Best Regards,
MrFixr55
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