03-20-2019, 10:03 AM
Ugh, I dislike that type of band-switch, very, very fragile. The solder tabs are hardened, any flexing and the tab will break off. Look carefully at the wafer and the metal housing. There should be three or four tabs from the housing that clinch the phenolic. The phenolic is accurately notched to accept the tab if it has been properly aligned. It looks like the one visible is slightly offset... I would not try to correct that as the phenolic could crack or the tab break.
To make a permanent fix and YMMV, cut off all the wires, attempting to de-solder in place will either cook the phenolic or break the tab. Take copious notes, of connections, take a couple of pix in addition to the one posted. Remove the switch, find a small clamp or large jaw pliers, back up the front of the switch so not to mar it and distribute the force, gently close the all tabs tighter on the wafer. De-solder all the solder tabs, remove all the wire bits. Rinse, even soak, the switch in 91% alcohol, that will remove all rosin that has crept over the phenolic. If you have some De-Oxit, spritz a bit inside the contacts and use a light machine oil on the bushing. Manipulate the switch at least 50 times, even 100. Check the continuity of all contacts in both positions. Set the meter for high resistance and check for dis-continuity on all switch positions as well as between poles.
Reconnect the switch...
If the switch is ruined, the schematic seems to say it is a multi-pole two position, these are easy finds, question is is it non-shorting or shorting. A meter will say.
I have looked through my copy of VIII I also find no reference to "Conventional Alignment" I DO find that topic mentioned in the next brand of radio Sentinel. However, it refers to specific Sentinel radios, not Sears...
Because "Conventional" is a broad term I would expect it to mean the alignment given to any other 4-5 tube superhetrodyne table radio.
Therefore: mechanical alignment of the tuner and dial indicator. That means replacing any support grommets that have either rotted or sagged. Align the pointer with the tuner fully meshed either to the last mark on the dial or some specific "oddly" placed mark on the dial.
I'm sure you know the drill of 30% modulation as low a signal as possible, use what ever signal strength indicator you like, output, AVC, etc...
Coupling to the generator to the radio can be tricky if there are tuning adjustment directly connected to the antenna terminal. In this radio the power line neutral is the "ground". The antenna terminal is couple via a link then through a coupling cap to line, therefore the RF return is either via neutral or L1 by flipping the non-polarized plug in the wall socket.
I would align this radio with it powered via an isolation transformer. Connect the generator hot to the antenna via a .0001 cap. That would load the coupling link similar to a 25 or more foot wire either connect the generator return to the chassis or leave it floating... That should allow for reasonably accurate setting of C1 & C2...
GL
Chas
To make a permanent fix and YMMV, cut off all the wires, attempting to de-solder in place will either cook the phenolic or break the tab. Take copious notes, of connections, take a couple of pix in addition to the one posted. Remove the switch, find a small clamp or large jaw pliers, back up the front of the switch so not to mar it and distribute the force, gently close the all tabs tighter on the wafer. De-solder all the solder tabs, remove all the wire bits. Rinse, even soak, the switch in 91% alcohol, that will remove all rosin that has crept over the phenolic. If you have some De-Oxit, spritz a bit inside the contacts and use a light machine oil on the bushing. Manipulate the switch at least 50 times, even 100. Check the continuity of all contacts in both positions. Set the meter for high resistance and check for dis-continuity on all switch positions as well as between poles.
Reconnect the switch...
If the switch is ruined, the schematic seems to say it is a multi-pole two position, these are easy finds, question is is it non-shorting or shorting. A meter will say.
I have looked through my copy of VIII I also find no reference to "Conventional Alignment" I DO find that topic mentioned in the next brand of radio Sentinel. However, it refers to specific Sentinel radios, not Sears...
Because "Conventional" is a broad term I would expect it to mean the alignment given to any other 4-5 tube superhetrodyne table radio.
Therefore: mechanical alignment of the tuner and dial indicator. That means replacing any support grommets that have either rotted or sagged. Align the pointer with the tuner fully meshed either to the last mark on the dial or some specific "oddly" placed mark on the dial.
I'm sure you know the drill of 30% modulation as low a signal as possible, use what ever signal strength indicator you like, output, AVC, etc...
Coupling to the generator to the radio can be tricky if there are tuning adjustment directly connected to the antenna terminal. In this radio the power line neutral is the "ground". The antenna terminal is couple via a link then through a coupling cap to line, therefore the RF return is either via neutral or L1 by flipping the non-polarized plug in the wall socket.
I would align this radio with it powered via an isolation transformer. Connect the generator hot to the antenna via a .0001 cap. That would load the coupling link similar to a 25 or more foot wire either connect the generator return to the chassis or leave it floating... That should allow for reasonably accurate setting of C1 & C2...
GL
Chas
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”
