I have an old Autohelm Wind Speed instrument (analogue direction with
digital speed) which no longer works. The direction needle moves, but does
not settle in any clear relation to the wind, and wind speed reads 0. I'd
like to see if there is any signal coming from the masthead unit before
going aloft and stripping the whole wiring out. Does anyone know what
voltages I should expect for the various wires coming down the mast? There
is a convienient junction box, so I don't need to cut into the wires to do
this.
TIA,
John.

"John Seager" wrote in message
...
I have an old Autohelm Wind Speed instrument (analogue direction with
digital speed) which no longer works. The direction needle moves, but does
not settle in any clear relation to the wind, and wind speed reads 0. I'd
like to see if there is any signal coming from the masthead unit before
going aloft and stripping the whole wiring out. Does anyone know what
voltages I should expect for the various wires coming down the mast? There
is a convienient junction box, so I don't need to cut into the wires to do
this.
TIA,
John.
I think the model is an ST50, if that helps.
J

John Seager wrote:
"John Seager" wrote in message
...

I have an old Autohelm Wind Speed instrument (analogue direction with
digital speed) which no longer works. The direction needle moves, but does
not settle in any clear relation to the wind, and wind speed reads 0. I'd
like to see if there is any signal coming from the masthead unit before
going aloft and stripping the whole wiring out. Does anyone know what
voltages I should expect for the various wires coming down the mast? There
is a convienient junction box, so I don't need to cut into the wires to do
this.
TIA,
John.

I think the model is an ST50, if that helps.
J


If I remember correctly, the speed is a pulse signal and the direction
is two signals with voltages corresponding to the SINE and COSINE of the
angle of the windvane. There is an 8 volt supply fed up the mast from
the display head to power the masthead unit and the direction signals
swing from somewhat above zero to a bit less than the supply. The
symptoms you have indicate a missing supply or ground to the masthead
unit. It may be a failed display head or bad wiring or possibly a
failed masthead unit.

The display head and masthead unit are often repairable (although
raymarine wont be any help - you need a good independent, preferably
working for beer money rather than commercially) and the wiring can be
replaced. If you do end up ripping it out, as the ST50 wind transducer
is discontinued, someone here may well be interested in it for spares.

wrote in message
...
On Fri, 13 Jun 2008 13:31:10 +0200, "John Seager"
wrote:

Before tearing your hair out, disconnect, clean and reconnect any
junctions you can access. This could be as simple as the ground shield
losing it's connection inside that junction box, or a loose setscrew.

Thanks. I did try that a while back but might have overlooked the shield,
thinking (in my ignorance) that this was not a critical component. Will take
another look.

While searching, I came across this from Stowe who make a replacement
masthead unit - 4th column seems to contain some relevant numbers. Not sure
what they mean by "2Ø 2-6V + wind speed" but I guess it would make sense
for the voltage to vary between 2 and 6 volts with increasing wind speed.
J
Specifications:

Model
Dataline
Micro
AH
NMEA

For use with Dataline, X, Navigator, IS11 Micro Autohelm ST50 Cetrek,
KVH, etc
Accuracy ~+/- 2? ~+/- 5? ~+/- 2? ~+/- 2?
Power Supply 12V nominal (7-16V) 12V nominal (7-16V) 8V nominal
(7-16V) 7-16V
Current 50mA @ 7V 50mA @ 7V 50mA @ 7V 50mA @ 7V
Output Type 3Ø 0-12V
+ wind speed
1Ø 0-7V
+ wind speed
2Ø 2-6V
+ wind speed
NMEA 0183 10Hz
or NMEA 0183-HS

"IanM" wrote in message
...
If I remember correctly, the speed is a pulse signal and the direction
is two signals with voltages corresponding to the SINE and COSINE of the
angle of the windvane. There is an 8 volt supply fed up the mast from the
display head to power the masthead unit and the direction signals swing
from somewhat above zero to a bit less than the supply. The symptoms you
have indicate a missing supply or ground to the masthead unit. It may be
a failed display head or bad wiring or possibly a failed masthead unit.

The display head and masthead unit are often repairable (although
raymarine wont be any help - you need a good independent, preferably
working for beer money rather than commercially) and the wiring can be
replaced. If you do end up ripping it out, as the ST50 wind transducer is
discontinued, someone here may well be interested in it for spares.

Thanks. This is more or less what I suspected but your detailed comments
encourage me to check the wiring again. It did work intermittently for a
while, which could imply a poor connection. It's such a nice instrument that
I am hoping to repair rather than replace - the modern analogue instruments
are pretty expensive. Unfortunately, the wiring runs through a very tightly
packed conduit up the mast which will have to be dismantled to get the wire
out. In the meantime, I'll check the visible ends.
J

"John Seager" wrote in message
...
Sorry, that should have read (if tabs work in Outlook Express):
Model AH

For use with Autohelm ST50

Accuracy ~+/- 2?

Power Supply 8V nominal (7-16V)

Current 50mA @ 7V

Output Type 2Ø 2-6V

+ wind speed

Temperature -10 to 50?C

John,
I am not sure this is relevant, but often more than one data inut can be
transmitted on a single wire like speed and azimuth, where speed is derived
as an ac signal (pulse rate) It could be riding on top of a dc reference
voltage used in azimuth calculation. These two pieces of intelligence could
easily be separated using capacitive coupling at the receiver.
Steve

"John Seager" wrote in message
...

"John Seager" wrote in message
...
Sorry, that should have read (if tabs work in Outlook Express):
Model AH

For use with Autohelm ST50

Accuracy ~+/- 2?

Power Supply 8V nominal (7-16V)

Current 50mA @ 7V

Output Type 2Ø 2-6V

+ wind speed

Temperature -10 to 50?C

On Fri, 13 Jun 2008 15:11:45 +0200, "John Seager"
wrote:

Unfortunately, the wiring runs through a very tightly
packed conduit up the mast which will have to be dismantled to get the wire
out. In the meantime, I'll check the visible ends.

You say the wires are in a raceway on the
inside of the mast? Can you follow the time honored Navy practice of
abandoning the old wires in place, and running fresh ones outside the
bundle. If you get zillion wire cables, they can swing around inside
the mast without breaking eventually. Tape them to the outside of the
mast, until it has to come down for some reason, and run the wires at
that time.

Casady

John Seager wrote:
I have an old Autohelm Wind Speed instrument (analogue direction with
digital speed) which no longer works. The direction needle moves, but does
not settle in any clear relation to the wind, and wind speed reads 0. I'd
like to see if there is any signal coming from the masthead unit before
going aloft and stripping the whole wiring out. Does anyone know what
voltages I should expect for the various wires coming down the mast? There
is a convienient junction box, so I don't need to cut into the wires to do
this.
TIA,
John.


If I get a chance this weekend I'll try to measure my ST50.

This spring I had the mast down so I replaced the cups and vane with a
kit I got from Defender for a reasonable price - $50 maybe? It was not
easy to get it apart and together; if I had to go up the mast I would
lower it down and have someone on deck deal with it.

"jeff" wrote in message
. ..
If I get a chance this weekend I'll try to measure my ST50.

This spring I had the mast down so I replaced the cups and vane with a kit
I got from Defender for a reasonable price - $50 maybe? It was not easy
to get it apart and together; if I had to go up the mast I would lower it
down and have someone on deck deal with it.

I didn't manage to check the wiring this weekend - took all day dealing with
a broken oil pipe. Had several litres of oil sloshing around the bilge! Will
get back to the wiring next time I'm at the boat.
J