I have this old National NC98 and when the voltage hits the band switch it was shorting out to ground. Now it measures 88 ohms to ground all the time so pulls down the B+. I have isolated the short to this one wafer on the band switch--measures 88 ohms to ground. Cannot see anything wrong with the switch but is 88 ohms to ground. I have never seen this happen to a band switch and how in the world do you repair it. Looks like it would be impossible to get out as there are three wafers on this one shaft and tons of wires.

John

Sometimes a wafer switch will arc over and carbonize. Carbon causes a resistive path. You might be able to did out the burnt area?

Norm

:I have this old National NC98 and when the voltage hits the band switch it was shorting out to ground. Now it measures 88 ohms to ground all the time so pulls down the B+. I have isolated the short to this one wafer on the band switch--measures 88 ohms to ground. Cannot see anything wrong with the switch but is 88 ohms to ground. I have never seen this happen to a band switch and how in the world do you repair it. Looks like it would be impossible to get out as there are three wafers on this one shaft and tons of wires.

Hi John,
I tend to favor Norm's idea. I cleaned a bandswitch on a Hallicrafters S-40 and turned it on still wet. It developed increasing "ignition static" noise over several minutes, which unfortunately turned out to be B+ beginning to make tracks through the phenolic. It finally arced over and shut down B+ to the RF stage. After deciding I would spend some time and effort on this radio - I meticulously diagrammed the entire wiring scheme for the bandswitch, since it ought to go back exactly the same way, then tediously removed the wafer with the B+ burn. I couldn't dig the burn out thoroughly enough to apply B+ to it, but I discovered the RF tube grid wafer happened to be identical, so I just removed it too and swapped them. After all that effort, the radio worked perfectly. Actual resistance to ground through the damaged wafer is megohms, so although it wouldn't have lasted long under B+, it won't affect performance in the grid circuit in my case. If your situation turns out differently, and you can't salvage your bandswitch, you might be able to talk someone out of a salvaged one.
Eddie

:John
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: Sometimes a wafer switch will arc over and carbonize. Carbon causes a resistive path. You might be able to did out the burnt area?
:
:Norm
:
:
:
::I have this old National NC98 and when the voltage hits the band switch it was shorting out to ground. Now it measures 88 ohms to ground all the time so pulls down the B+. I have isolated the short to this one wafer on the band switch--measures 88 ohms to ground. Cannot see anything wrong with the switch but is 88 ohms to ground. I have never seen this happen to a band switch and how in the world do you repair it. Looks like it would be impossible to get out as there are three wafers on this one shaft and tons of wires.