I have a 40-180 that is driving me crazy, it has been worked on before I corrected some problems my last problem is no tuneing in manual mode push buttons work and can be tuned.I have checked everything in the circuit at least 3 times and replaced and jumpered caps in the osc circuit I cannot get the circuit to oscillate it is not that complicated a circuit has anyone run into this problem? I’ve included a schematic I checked the coil wireing at least 5 times any input is appreciated.
I have been pondering on this. Considering that your radio works on the push buttons, but not on main tuning, that tells me that most of your circuits are working OK. Now, when you use a push button, the switching cuts out the RF and oscillator coils from the main tuning, and cuts in a different set of tuning specific to that particular push button. Check the continuity and wiring of the antenna coils in #1, and #2, and also #18, the oscillator coil in the chassis. Problems with these, especially #18 could cause the symptoms you are experiencing.
We're on the right track with the switches and oscillator coils. When in manual mode the oscillator uses the transformer 18 coils to oscillate and one of the tuned coils on the left when in push button mode. The two sets of slide contacts on the right side of the push button switches do this selection. You'll have to find them by identifying the parts connected to the terminals. As noted above the oscillator transformer 18 should have continuity in the primary and all three secondary windings. Make sure there is continuity between A5 and A3, A6 and A2, A6 and A4 when the wafer switch is rotated. Maybe hit all the switch terminals with a soldering iron and a touch of solder.
Without the last pushbutton on the right side pushed in, you will not be able to tune in stations manually. That button is for dial tuning. If it's popped out, only the pre-set buttons will work.
Just throwing that out there. There have been at least two or three other people in recent years with 40-180's falling silent because of that dumb button that needs to be pushed in. It happened to me with mine when I had one.
I’m at whits end can’t understand why this simple circuit won’t oscillate I’ve substituted all caps including tuneing cap & grid leak resistor checked coil resistance and connections, i can make it osc but with almost no tuneing by increasing cap 19a by 150mmf can even disconnect tuneing cap same result. Switches all working normal.removed wax from osc coil checked windings I can’t think of anything else to check. Anyone have any ideas? Push buttons working normal.
Forrest
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I was working with Forest on this. Here is the strange twist. If We take the wire off of #1 of the oscillator coil and connect it to #4 we can receive the AM stations between 540-1130 but not beyond that. The coil ohms out as per the schematic. Not running into this before is it possible that the coil inductance is bad even though the resistance is ok? The push button switches work fine it all seems to be centered in the oscillator coil. Does anyone know what the inductance reading of that coil should be?
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