The dc resistances will be something like 60 ohms for the input side and 200 ohms for the output of the tank.
The drive circuit of the amp places the reverb tank input coil into the feed back loop of the driving opamp. This means that neither end of the input coil is grounded and trying to listen to a signal from the reverb drive cable will not give normal results.
If the tank checks ok and the connections to and from the tank are all good, then check the return circuit of the amp either by touching the tip of the return RCA plug or by shaking the tank. If that checks out, then replace the drive opamp.