Autohelm

[richardabeattie]

I have an elderly Autohelm 1000 which appears to be bust. When I open it up and put 12v directly to the motor the ram moves in and out (depending on polarity). But when I put 12 v in via the plug, and thus via the electronics, the ram will move inwards but not outwards. Its plug has two pins.

But I also have what is probably an even older model called AH800 which may or may not be serviceable but which has a three pin plug. Why three pins? If I cut off the plug and put the Autohelm 2 pin plug on it which two of the three wires do I connect and will it work?

 

[earlybird]

The AH800 should have only 2 wires, red (+ve) and black (-ve.) the third connection in the plug is unused.

 

[richardabeattie]

There are three wires in the plug - brown+, blue- ,and earth. Can I replace the plug with the two pin Autohelm 1000 plug and cut off the earth wire?

 

[earlybird]

No idea what the earth wire does. I'm fairly sure it's not original. Maybe the cable has been replaced.
The AH800 is pretty old, later versions of the Tillerpilot did use brown and blue but non had separate earths IIRC.Here's the manual

 

[ProDave]

A service manual is available for the AH100-/2000 there was a thread last week giving links to it.

the motor is driven by a H bridge formed by 4 power transistors. If it will only drive one way probably one or more of those transistors is dud. Try replacing all 4.

My interest is more with your AH800 I have a dud one that is the main PCB I am on th elook out for one with a working OCB but dud mechanics.

 

[Praxinoscope]

There seem to be quite a few Autohelm owners looking for replace,ent PC’s, I have been trying to find a replacement for a ST1000/2000 for ages. Trouble seems to be the electronics go before the mechanics.
A further difficulty is that the w/s manual only covers the mechanical aspects and lists components, it doesn’t suggest what to do in case of a PC fault it just says ‘replace’ which is fine if you are Raymarine but at over £170 a board it’s not so good for home repair.

 

[richardabeattie]

Definitely an AH800 with original three wire cable, brown, blue and yellow.

 

[richardabeattie]

AH800 puzzle nearly solved. There are three wires at the plug, definitely original equipment, but the earth wire is cut off where it emerges inside the unit near the printed circuit. Why did they not use a two wire cable? Now all I have to do is to extend the cable which is just 3 inches shorter than the Autohelm 1000 cable which itself was only just long enough. I want to be a value engineer when I grow up.

 

[andsarkit]

On my original Autohelm 1000 (with the rotating compass ) the power transistors had tall vertical brass strips for heatsinks. I suspect that while motoring these resonated and the solder joint on the leg of the transistor failed. After resoldering the joint I fitted low and wide aluminium heatsinks and didn't have further problems.

 

[ProDave]

Can someone with a working AH800 please measure the current drawn from the 12V input when the unit is powered up but in standby please?