Here's a few pic's of the tuner that De Oxit won't help. But works on one channel!!!
Terry

If it's sufficiently hopeless that it needs to be replaced, maybe you could make this bad tuner a channel 3 only tuner. Solder the switch contacts permanently to the channel 3 position, and feed this TV set with a DTV converter box set to analog channel 3 output. Analog over the air TV is going away next Feb anyway...

When a good tuner comes around, just replace the channel 3'ed one with it.