I've got a unit that is about 7 years old.
Recently, it started turning erratically, causing the display to
pop the Antenna not rotating message, and shutting off.

The antenna's turning, but slows about every 1 to 1.5 revolutions.

I've changed the belt, and had a good look at the unit. It appears
clean, and uncorroded.
I'd like to suspect the stepper motor, as that would be a pretty cheap
fix, but before I go there, I'd like to hear some opinions of what
else might
be causing the stepper to speed up and slow down like that.

TIA

In article ,
says...
I've got a unit that is about 7 years old.
Recently, it started turning erratically, causing the display to
pop the Antenna not rotating message, and shutting off.

The antenna's turning, but slows about every 1 to 1.5 revolutions.

I've changed the belt, and had a good look at the unit. It appears
clean, and uncorroded.
I'd like to suspect the stepper motor, as that would be a pretty cheap
fix, but before I go there, I'd like to hear some opinions of what
else might
be causing the stepper to speed up and slow down like that.

TIA

I would highly recommend calling Raymarine and talking about this with
one of their techs.

A couple of years ago I had a bad mosfet chip on my scanner pcb and they
helped me diagnose it, isolate it and point me in the right direction
for a $4 part that fixed it.

If you get someone whose not so helpful, call back another time and try
again.

jps

If this is just a simple motor, pulley and belt drive, look for the pulley
slipping on the motor shaft. They used a press fit on early motors, no set
screw or key. I have had no luck with peening the shaft or using a thread
tightner glue (Locktite). Also it is very easy to damage the motor trying
to fix the problem. Raymarine's solution...buy another motor with attached
pulley and swap it out.
Doug K7ABX
"jps" wrote in message
...
In article ,
says...
I've got a unit that is about 7 years old.
Recently, it started turning erratically, causing the display to
pop the Antenna not rotating message, and shutting off.

The antenna's turning, but slows about every 1 to 1.5 revolutions.

I've changed the belt, and had a good look at the unit. It appears
clean, and uncorroded.
I'd like to suspect the stepper motor, as that would be a pretty cheap
fix, but before I go there, I'd like to hear some opinions of what
else might
be causing the stepper to speed up and slow down like that.

TIA

I would highly recommend calling Raymarine and talking about this with
one of their techs.

A couple of years ago I had a bad mosfet chip on my scanner pcb and they
helped me diagnose it, isolate it and point me in the right direction
for a $4 part that fixed it.

If you get someone whose not so helpful, call back another time and try
again.

jps

In article ,
(C. Sadler) wrote:

I've got a unit that is about 7 years old.
Recently, it started turning erratically, causing the display to
pop the Antenna not rotating message, and shutting off.

The antenna's turning, but slows about every 1 to 1.5 revolutions.

I've changed the belt, and had a good look at the unit. It appears
clean, and uncorroded.
I'd like to suspect the stepper motor, as that would be a pretty cheap
fix, but before I go there, I'd like to hear some opinions of what
else might
be causing the stepper to speed up and slow down like that.

TIA

A few of things to look at:

1. Do you actually see the antenna slowing down when it is
turning? Check the motor drive elecronics if it does.
2. The feedback signal from the antenna to the display is usually
a pulse stream that is generated by the motor, or some type
of chopper wheel - LED/PhotoDetector system. Put a scope
on this pusle train and see if it is changing frequency
When the motor slows down. Chopper wheel holes can get
plugged up with water or particals, and cause the pulse
train to be missing a few pulses/Rpm and cause your symtome.
3. Check for intermitant shorts, or opens, in the Feedback
Signal Wire, from the antenna to the display.

Bruce in alaska
--
add a 2 before @

C. Sadler,
Did you spin the antenna by hand? Did you feel any binding or high
spots? If so you could have a bearing that's going, if so you need to remove
the belt to see if it's in the antenna part or the motor. Is there a way to
grease or oil the rotating parts, I'd check with the manufacturer on this? I
admit that I don't know radar systems, but I'm familiar with stepper motors.
They're generally not used it this type of application, they're used as far
as I know to turn the motor shaft a certain amount of degrees, usually in
either direction and at variable speeds to position things. I'd suspect that
you have a regular DC motor designed or geared to a specific rpm.
Paul

"C. Sadler" wrote in message
m...
I've got a unit that is about 7 years old.
Recently, it started turning erratically, causing the display to
pop the Antenna not rotating message, and shutting off.

The antenna's turning, but slows about every 1 to 1.5 revolutions.

I've changed the belt, and had a good look at the unit. It appears
clean, and uncorroded.
I'd like to suspect the stepper motor, as that would be a pretty cheap
fix, but before I go there, I'd like to hear some opinions of what
else might
be causing the stepper to speed up and slow down like that.

TIA

The motor problem as described sounds like a simple motor failure.

I had the Raytheon factory repair my unit last year and the charge to
replace the motor was about $175 including return shipping.

Rich

"Paul Schilter" paulschilter@comcast,dot,net wrote:

C. Sadler,
Did you spin the antenna by hand? Did you feel any binding or high
spots? If so you could have a bearing that's going, if so you need to remove
the belt to see if it's in the antenna part or the motor. Is there a way to
grease or oil the rotating parts, I'd check with the manufacturer on this? I
admit that I don't know radar systems, but I'm familiar with stepper motors.
They're generally not used it this type of application, they're used as far
as I know to turn the motor shaft a certain amount of degrees, usually in
either direction and at variable speeds to position things. I'd suspect that
you have a regular DC motor designed or geared to a specific rpm.
Paul

"C. Sadler" wrote in message
om...
I've got a unit that is about 7 years old.
Recently, it started turning erratically, causing the display to
pop the Antenna not rotating message, and shutting off.

The antenna's turning, but slows about every 1 to 1.5 revolutions.

I've changed the belt, and had a good look at the unit. It appears
clean, and uncorroded.
I'd like to suspect the stepper motor, as that would be a pretty cheap
fix, but before I go there, I'd like to hear some opinions of what
else might
be causing the stepper to speed up and slow down like that.

TIA