Hi, We have a model J-150, the circuit keeps triping in the control box.The motor is not frozen or blocked,it spins free untill the breaker trips. PLEASE HELP !

I've been reading old posts here for the last couple of weeks, and I think you all ahve helped me solve my problem. Before I go spend a couple hundred dolars I'd like to check my work with you if you don't mind. I have a 27-year-old drilled well. My neighbor thinks it goes down about 75 feet, but I don't know. The water level is less than 8 feet from the ground. In my basement there is a 10-year-old Sta-Rite/Con-Aire 19 gal(?) bladder tank with a shallow well pump on top. The pump used to be a 5/8hp at 30/50 or 40/60, but two or three years ago it died and I replaced it with a 1hp Craftsman pump with a 40/60 switch running closer to 44/78. I've always called it a "jet pump" but there is only one line going from the well to the pump so I think this is techically incorrect. A few weeks ago we started having intermittent water supply problems, including a slapping sound in the pump as it came on and tried to get water moving (this is "cavitation?"). Air came out of our faucets along with sediment (looked like rust) in the water. A well contractor suggested (over the phone) changing the foot valve due to age and because it's a common cause of cavitation problems. I told him the well side of the pump had water (there is a check cp near the pump intake) but he said "it doesn't take much" and suggested that even though I couldn't see any loss of prime, there could be a slow foot valve leak... I am willing to change the foot valve, but if I have to I'll have some questions first. Before going there, however, I checked the pump prime (OK), drained and precharged the tank (it was in the mid-20s so I added nearly 20psi to get close to my 44psi cut-in), reconfirmed there was water in the supply line (there has been water there all along). After that nothing changed, so I drained and re-primed the pump and poured water into the line from the well both inside the house and out at the well head (through the vent -- is that OK?), just to be sure. Still no change. At this point I feel that I've ruled out any but the slowest foot valve leak and the pump is not losing its prime. However, I noticed that after draining and recharging the bladder tank things got worse, especially the slapping sound when the pump comes on. The pump bucks and jumps, and the pressure gauge just waves back and forth between 40 and 60 or so while the pump runs continuously. If a tub faucet is running the whole system can lose pressure and the pump does not seem to be able to recover. It ends up around 20psi at the pump and the plumbing pipes deliver a trickle if anything. If I shut the pump down and close the valve between the system and the bladder tank, the pump can re-pressurize the plumbing pipes as if everything were normal. Today, from a fresh start, if I close the valve leading to the air/water tank, effectively eliminating it from the system, everything seems to work fine. The pump comes on and runs continuously when we use water, but it does not have the "slapping" problem and it is able to move enough water to keep up with the demand. The pressure gauge hangs around 75psi while the water is running and settles in the mid- or upper-60s after we turn the water off. If I open the valve to the bladder tank -- slightly -- I can hear it filling with water, and the pump is able to fill it as long as I keep the flow rate low. Then we can run tap or tub water and delivery is smooth until we get down to the pump's cut-in pressure. At that point if I've left that valve open the pump will slap and buck when it starts up again, and we are back where we started. Does this make sense? Right now I have left it set up with the valve closed and the system works fine -- the pump is just running more than one would like, and there is some surging at the faucets when it kicks on. But as long as the bladder tank is cut off from the pump and plumbing system, everything seems to work OK. Is it time to replace this tank? Is the same tank OK (around $150, I think)? Sorry about the long post, and thanks in advance for any replies. at least 75% of what I've done so far has been based on ideas from this site. I can't thank you all enough. There is no way I could afford to have someone come in and take care of this for me.