Three common failure modes

failing to rotate

particularly older R-50 rotors

leakage - riser seal failure

sand - maintain a small moat around heads to reduce wear
can replace riser without fully digging up outer shells
1804 riser seals leak more with lower water pressure

mower damage

bury deeper

nozzle failure

they are replaceable

Two flavors

5004 with check valve

3/4" pipe thread, nozzle inserts in head
head is integrated with riser

1804-SAM   R-VAN instructions

1/2" pipe thread, R-VAN head with nozzle screws into riser

2019 RainMachine Mini-8
Powered from golf cart outlet..Supplied 24V 750mA transformer measures 31.2V open circuit
(ESP-6 transformer measures 30.3V, rated 26.5V 40VA)
Mini-8 runs OpenWRT on AR9331
http://linuxgizmos.com/tiny-wifi-loaded-openwrt-com-starts-at-12/
https://wiki.openwrt.org/toh/tp-link/tl-wr703n/ar9331_pinout
https://www.openhacks.com/uploadsproductos/ar9331_datasheet.pdf
Atheros AR1311 seems to be a newer revision of AR9331 

At power on, wifi symbol flashes, then dark while pausing,
then 7 segment display circulates for awhile
then buttons light
then all goes dark

Needed a reset (press 5 seconds, wait for beep) to display "A".
Initial Wi-Fi setup here:
RainMachine Mini-8 Setup - YouTube
https://www.youtube.com/watch?v=XVfDnEg0hLk

Unit was previously configured by/for some Texas location..
Setup is not sequential, must be navigated
First set iOS WiFi to rainmachine
then devices in app - password setting requires enter key to register
then settings in app for real wifi setup 192.168.1.23
then app hangs when trying to access device - firmware updating?
(button lights cycle)
Mistake to allow auto detect location - 2 Ferebee instead of 8 Ferebee..
Access from chrome browser works - cmR18722!
Enabled Beta updates and selected 4.0.945
Setup restrictions to not water Sunday or 00:01-10:01 Monday

Direct access from web browser seems nicer than iOS app..

Sprinkler controller is mounted on wall facing West, a no-no..

Transferred (except start time) from RainBird ESP-6
Prog A: On Wed+Fri+Sun start (60 minutes before sunrise)
Zone minutes
1 01  drip
2 10 garage front
3 10 bedroom front
4 10 garage rear
5 0   same as 4
6 10 bedroom rear

Irrigation controller transformer gets power from golf cart circuit breaker.
As hoped, Mini-8 decided no sprinkling needed this week..
ESP ground connected to common; spliced into Mini-8 rain sensor common.
Rain sensor configured normally closed (opens when rain is detected)

Aug 13, 2019
------------------
 Changed program from Wed+Fri+Sun to every 2 days,
so perhaps 7/14 instead of 6/14 potential watering every 2 weeks.
Consequently, reduce times by 1/7 (multiply RainBird values by 6/7)

zone sq ft  min:seconds
1        200 0:51  drip
2      1700 8:34  garage front
3      1000 8:34  bedroom front
4      4350 8:34  garage rear
5      (0)    same as 4
6      6000 8:34  bedroom rear

Configured custom zone flow rates to force suggested program times
17032 sq ft, according to plat,
front yard approx 40x25  ~ 1000
garage side approx 15x90 + 25x15 ~ 1350+375 ~ 1700
rear gar side 30x112 + 43 x 23 ~ 3360 + 989 ~ 4350
rear br side   68.5 x 88 ~ 6028
approx 13000 grass

Aug 14
---------
Program soaked, but still front runoff.
Increased zone 2 & 3 slope
Moved zone 6 before 4 for more consistent sequence.
Much more yard watered on bedroom side...

Property ID (PIN) R600 020 000 0655 0000

Aug 15--------- - no watering today, because every 2 days
no water scheduled tomorrow because adaptive frequency skip
changed program from every 2 days to daily
then no water scheduled tomorrow because expected 1/2 inch rain
home graph shows 62% watering today (but too late for it to run)
Zone 1 shows much greater field capacities than others for the same soil type,
presumably to compensate for difference between grass and trees/shrubs,
which want more water but less often... 

"Better results on saving water can be obtained
 if your program frequency is less than 3 days."

Per bottle test, about 1/4 silt, 3/4 sand -> "Sandy Loam"
-  but that was mostly from sod root layer
In Zones, changing soil types from silty clay to sandy loam
 did NOT change recommended daily times...
Increased all Minimum Rollover Threshold (from 0),
 more in rear to avoid e.g. 2 second cycles
and allow rear lawn sprinklers time to rotate..

Aug 16
---------
83% today, because neither rain nor watering yesterday.
No soak, presumably because soil type changed from silty clay with 0.15
to sandy loam with 0.4 intake rate.  In reality,
 despite bottle test, soil is mostly silt on top with sand under,
 so should probably set custom type but instead increased slopes to high..

Sep 4
--------
Switched zone 6 to alternate days, increased time
(some grass patched browned last week)

Sep 24
---------
Zone 4 wraps around behind living room, bumped to program 3 (alt days)
  and zone 6 Precip rate (2 in/hr)
Programs ran @ 11 AM (Monday after mowing)

9 May 2022
----------
ordered Rain Bird
 5004-FC (x2),
 5004-PC-SAM (x3),
 1804SPRS-RVAN14 (x4)

20 May 2022
-----------------
Zone 4 replaced full circle head, reduced nozzle from 5.0 to 4.0,
with much less screw protrusion, deflecting less water near the head.
Leaking Zone sprinklers at curb west of driveway
had been replaced June 2019.. but NOT SAM; replaced now by 1804SPRS-RVAN14s
RVAN adjust: left is fixed (see line) push down and rotate rotor for right side.
Collar below adjusts pressure/distance.

Spread lime on front yard bare spots, tweaked RVANs for more coverage.
Sprinkler by front bedroom window is too strong...
Changed zone 2 front slope from high to very high for longer soaks
and hopefully less  runoff...