Possible to repair Hunter PGP heads?
 

I have a sprinkler system with 4 zones and a mix of mainly Hunter PGP heads
(90%) and some Toro heads that have been running forever according to my
neighbor who was around when the system got installed 20+ years ago. The
controller is a Rainbird 7i also from 20+ years ago. All mechanical parts. It's
a bit noisy but it's supposed to be a workhorse, though I had to replace the
motors in it this season.

In fact, this season has been a nightmare. The controller died, I mangled a line
while pulling out a tree root, station 1 will not operate (I suspect the
solenoid went but don't have a fault finder to find the underground connection)
and the service can't come out until the end of the month and several heads were
non-functioning this year.

So, I had to realize that every season I'm replacing 1 to 3 heads without fail.
They're not expensive but for 90% of them, they just stop turning. That got me
to thinking that perhaps there's a more economical way to deal with this. Can
these heads easily be repaired to go back to proper rotation? In most, if I turn
them back to one side, they'll turn, return and then stop. Some won't rotate at
all any longer. Or is my only option to just keep buying new ones?

In the repair I made for the broken PVC line, the Hunter head was working just
fine until I repaired the line and re-aligned it. Upon screwing it back in, it
was completely out of alignment. I did this with the water on which I've now
read is a possible cause, though I've seen the irrigation guys do this all the
time.

Any help would be greatly appreciated.

*** RTH ***