Drive pin stays down.i have replaced o rings and cleaned.

You need to either replace your pan assembly or buy a new machine

If all of the o-rings have been replaced in the gun then one (or more) of the new rings was either installed in the wrong place, moved or was damaged when the gun was reassembled. When installing o-rings make sure they are very well greased with the lube that comes in the rebuild kit and that all are replaced exactly where they belong.

is the cylinder really dirty, if so it needs a thorough cleaning. your instruction mnual detailes how to do this. also look for a jammed nail in the nose area and possibly a bent driver.

Look for the plunger coming out of the frame where the door hinge is. Is it broken? When you open the door the plunger is released (comes out) and grounds sending the signal to chime, however this should only happen if your lights are on or key is in. The chime controller may have failed and that's why it also could stay on. Does it happen when the key is in, while driving, or even always stays on? Need more info.

Sounds like you need to adjust the valves.

If the driver moves on it's own then it's o-ring is shot,replace it. Pop the feeder cap and clean all the roof crud that's built up underneath it.Now you can see the feeder spring,check to see if broke or old and replace.The feeder plunger is air assisted so hook the air up and depress it, it should depress hard and pop right back up. If not it needs to be cleaned and new o-rings. If this doesn't work then it's a new feeder plate you need. good luck.
5run7

yes there is an adjustment. follow your shift lever down and you will find a block of iron with 2 bolts holding it. you will also see ond the lever itself a spring loaded pin.most of the time this pin gets gummed up and does not engage the block completely.clean and ensure the pin moves freely. if this does not solve the prob then the block can be moved up or down by loosening the bolts.

Using a wire "toothbrush" size brush, clean the track in front of the gun where the pin slides - where the nail groove is. **** particles from the nails and the plating from the nails sluffs off fouling the path and causes the pin to stick. After several cleanings of my gun, I noticed that this brushing of the track the firing pin follows keeps it operating for several days without the problem recurring!

The check valve is what causes the pin/driver to return to top of cylinder. To check if it is in place, remove the cylinder from the gun and look for an oring/band installed on a groove. This groove should have vent holes drilled thru the cyl. Holes should be clean. Any oring or rubber band can be used here. Just tight enough to stay in place. Other things to check:
Pin/driver should fit snuglly enough to hold it's own weight in cylinder. If your gun uses a plastic ring, it may be replaced with a rubber oring. Just make sure that the piston travels freely but holds its wieght.
There should be a bumper and a washer in the lower part of the gun. The bumper should not have any cuts or missing pieces and the washer should fit snuggly around the driver blade to prevent air from leaking down thru bottom of gun. If air is leaking down thru bottom, there is less pressure to push driver up. Email if you have more questions, good luck with your repair.

ok im going to take a shot at this its been a while since ive been in a school kitchen
with the planetary ring its supposed to be tapped in make a jig by getting a 2x6 board and 2 2x4s they dont have to be long screw the boards together with the 2 2x4 standing 4 inch up across from each other about the size of the blender head
the wood is to support mixer while on its head and to keep from teetering around
put down down a piece of foam
put the mixer on its head upside down
now you have to find an old plastic sturdy made cup the size of the ring its gotta be able to take a beating (the cup)
but not a hard beating this will help in seating the panetary ring
now get another piece of foam
glue to top of cup let dry then trim around the cup evenly out side and on the inside leave a little foam over the inside edge
place ring on planetary drive where it goes put cup over ring make sure the cup matches size of ring
now get a wood rubber or small pin hammer and tap lightly on the cup till the ring sits itself back into position this is the safest way to place the ring
use a little appliance greese on inside ring lightly to help ease into place

now if any part of the ring is bent i dont recommend placing of old ring i would suggest buying a new ring for mixer