These units are functionally compatible to both the TR3 and 4. To have the RV4 work with TR3 only a minor change is required. Both units use a 12AU7 in the buffer stage. The RV3 uses a 6AU6 for the oscillator; the RV4 is solid state using an FET. The RV4C uses the dual dial plates common to all the C line and the SPR4.

    The RV3 will work with the TR4any, but the RV4 will not work with the TR3 unless the TR3 is modified. On the remote VFO plug on the TR3, cut the jumper wire running between pin 2 and 8. If in the future you remove the remote VFO, you must restore the jumper or make up a dummy plug from a Cinch Jones connector.

    Summary of Remote PTOs