Back to your plane with the receiver that does not appear to work. If you look on the back of the radio, there should be a sticker with a 2-digit number on it. That is the "channel" or designator for the frequency that your radio transmits on. If you look on your receivers, you should see a small, plug-in crystal (see pic) which has a tag on it which also displays a channel number. The receiver channel number has to match the number on the back of your transmitter in order for it to communicate with the transmitter. Its possible that at one time, there was a second transmitter (on a different channel) that your granddad used for the other plane. If the number on the receiver that does not work is different than the one on your transmitter, you can buy another crystal with the correct channel number and replace the one in the receiver. They are only $10-$15 each but are getting hard to find now that most people have gone over to 2.4GHz systems.
