HELP ! BP Power Down feed broken

[CNC OT]

My bridgeport (vintage 1966) will not power down feed. When the leaver is engaged, it will not stay in, rather it pops out. The micrometer screw assembly is NOT the culprit. The Handle turns, the Forward /Reverse lever will not stay engaged. but even though the leaver is held to the left the quill will not feed up or down. The power feed used to work.
What is most likely wrong? What steps do I take to disassemble the mechanism to find worn parts? The manual says not to touch the clutch assembly . It is factory set to 200 pounds.
The drawings are confusing. I cannot tell what to remove in what order.
Can anyone help? I have spent hours searching and reading the old manuals, but I can find no instructions.

[MR Custom]

look for a sheared key on the input shaft. Also look at your clutch it may have just kicked out it might just need to be reengauged I seen this sort of thing happen a couple times on an old tape drive chucker lathe when we would try and take to big of a cut.

[CNC OT]

Thanks, Mr. custom
Wht do I remove in what order to inspect the key? I do not know what you mean by the "input shaft" If You have a BP manual could you reference the find numbers? "What do you mean by "look at the clutch" It will not stay engaged. Do I remove the clutch starting at the trip leaver, and what do I look for? I have never dissembled a BP. I can follow the manual maintenance instructions for the motor, etc. but they are none for working on the down feed. I fear there are some "tricks" or methods which one cannot figure out from the drawings alone.

[MR Custom]

Did not mean to add to your problem.

[machintek]

The quill downfeed is the last bunch of parts that gets removed in a total head rebuild. There are a lot of hidden set screws that hold a lot of parts from coming out too, just it make it a bit more frustrating. Step by step directions would require a small book.
It is best to understand the flow of mechanical motion and see where it stops to determine what is wrong.
The splined gear hub (that drives the spindle shaft) drives a cradle that can swing in and out to turn the quill feed. Motion travles down to the gear box on the left side of the head. Here you select a feed per revolution. Motion jumps the the mating vertical shaft and moves down to a bevel gear with two mating gears (one in front and one behind it). One of these gears is chosen by pulling or pushing the inner center shaft sticking out the front. The one that is always broken off and replaced with a screw. The push pull motion moves a collar with 4 teeth on each end that grabs one of those bevel gears. There is a 1/16 inch roll pin that the collar is moved with and also trasnmits motion to the outside shaft. So here is the first weak link. motion is transmitted to the end of this shaft where there is a worm gear with again an undersize pin. This is the second weak link. Here it drives a pinion gear attached to which is a clutch. swinging the hanging lever to the left engages the other half of this clutch which has the spring governing the force applied to the quill and protecting the previous parts.
There are a LOT of adjustments that makes all of this work correctly. Including the disengage mechanism associated with the quill micrometer stop screw.

George