Diode Autohelm

[Kastrup]

Hi
Capt dan are right, my computer is 24 volt.
the fifth transistorte on the main part of the computer have the serie no.
(from the where the main power comes in)
1. MJ11029 C1435
2. MJ11028 SM9109
3. MJ11023 SM9147
4. MJ11029 C1435
5. MJ11028 C0315

I do not now if any of these are related to clucht.
Any way I have decided to change the BDW94W switch diode on the lower board. I’m not sure that’s problem, but now I try.
It will take the supplier 2 weeks to get it home, so when it’s installed I will be back with the reslut

[Capn Dan]

Take the BDW94 to any electronics repair shop and ask for a similar transistor. It is a "PNP" type, about 10 amp. They should be able to get something similar. They are also available on ebay for a few dollars. You can use any BDW94. It does not need the"W".

[gello]

if the BDW94W is a 10amp then that is ample to control the clutch directly.
Hopefully they put a diode across it to clamp the switching transient when
that PNP cuts off on the clutch inductance. Need to check the diode as well.

I leave it to you capn dan. you obviously have more information on the 7000
than i do. I was working from the 6000 spec and a lot of guesswork and intimation.

cheers

gello

[Capn Dan]

Gello,

The way I look at it is the cost of a few transistor is so low that it is easier to replace that test. It is fairly easy to trace the circuit with an OHM meter.

This is an odd problem in that the clutch power remains on when it should cut off. It certainly is possible that the main processor is not working properly or that the diodes and transistors between the MPU and BDW94 are bad.

Why would the clutch activate and then not cut off? I would think that it would be more likely to either be faulted on or off, not going from off to on and staying that way. Thoughts?

We are also operating under the assumption that power is remaining to the clutch and it is not simply a sticking clutch.

Dan

[gmau]

Originally Posted by gello

in response to some private messages,
the schematics i have are for a 6000 autopilot.
i posted them for download on the web at
http://www.baldriver.com/repository

as to the autohelm issue.
pardon me for being basic

I am assuming when you kill power to the unit the clutch releases. (true?)

when the unit is on, clutch engaged, and you hit standby,
does the unit continue to try and steer or does it quit
steering but leave the clutch locked? (trying to ascertain
control unit versus interface).

does your main unit have a row of large transistors
in silver cans or with metal tabs on a heat sink? if so, how many of them are there (should be 0, 4, or 5 depending on the computer.).

(looking for the clutch control transisitor unless for some
odd reason raymarine went back to the expense and reliability
issues of relays in their new units.).

gello

Thanks for posting the schematic.

Gordon

[gello]

agreed.
i just usually have limited spares onboard and don't want to take a chance
of blowing one till i find the actual fault. with access to shoreside spares,
sure, replace. if it pops again, then keep looking.

you are right, it is puzzling that it would behave until activated once.
especially if the rest of the autopilot is still functioning (i.e. it is
not clamping the processor due to overcurrent. if the processor
also quit functioning then it would make more sense).

the only explanation that comes to mind immediately is so
far fetched i hesitate to mention it.
could be that
the transistor is damaged and the inrush current when the clutch
is activated is punching through the base of the PNP
or zenering the junctions effectively shorting
it when it is under load. makes it act like an SCR.

the diode across the
clutch coil used to disssipate the transient when the transistor turns off
would be in the wrong direction or i might suspect it of zenering.

i would look at the driver circuitry first, that explanation is just too wild.

capn dan has it right.
replace the transistor, see if the problem goes away.
if not, start checking drivers back to the processor.
should be simple as i can't imagine a very complicated path between
clutch and processor output pin. not much else dependent there.

come to think of it, put a voltmeter across the clutch and see if the
voltage is switching on and off or not.
If its a sticky clutch, you got the wrong boy here.
I rustle electrons, if its big enough to hit with a hammer you are out of
my job description.


g

[Kastrup]

Hi
Thanks a lot to gello and capt. Dan
Your input has been very interesting reading.
To capt dan.
What is MPU a abbreviation for ?
Do you know where the main processor for clutch is placed on the computer ?
And to avoid any kind of misunderstanding, it is not the driver or the clutch coilthat Is my problem, I have testet that part and it is working perfect.
It is the switch ( or something else) in the computer, that have to turn the power of, when you push the STANDBY button on the display. As soon as I put power on the computer, and even it is on STANDBY on the display the clutch is activate.
Kind regards
And again, thanks for the input

[Capn Dan]

MPU = Microprocessor unit = the "brain" or where the operating program is. On this unit it is an 80C32. They do not go bad very often and it will control the clutch.

Have you tested the BDW94?

[goboatingnow]

Originally Posted by gello

(looking for the clutch control transisitor unless for some
odd reason raymarine went back to the expense and reliability
issues of relays in their new units.).

gello

Because Ray had a persistent problem with the driver transistors failing in the previous model.

Dave

[Kastrup]

Hi
Now i have got my coursecomputer back, the BDW94 diode has been change. I have tested it, and unfortunately that was NOT what was
wrong. The clutch still lock the wheelsteering when i push the standby
buttom.
So now i don't what to do, any/all suggestion are welcome.
kind regards

[svBeBe]

I have a question for Kastrup and a wild guess for you.

Is this installed on a 24 volt boat and is the drive unit Raymarine? If so, how do you have the clutch fuse inserted on the course computer? It will insert in either a 12v or a 24v slot.

All Raymarine clutches are 12v and they do not make a drive with a 24v clutch even when the drive motor is 24v. The 12/24v clutch fuse/slot option on the course computer is for installations including drive units other than Raymarine. If you have the fuse inserted in the 24v slot, and the drive is Raymarine, the clutch will overheat and can intermittently lock. If this is the case, the clutch will need replacing because the damage has been done.

Like I said, this is a wild guess, but sometimes you can never tell.

Bill

[Kastrup]

Originally Posted by svBeBe

I have a question for Kastrup and a wild guess for you.

Is this installed on a 24 volt boat and is the drive unit Raymarine? If so, how do you have the clutch fuse inserted on the course computer? It will insert in either a 12v or a 24v slot.

All Raymarine clutches are 12v and they do not make a drive with a 24v clutch even when the drive motor is 24v. The 12/24v clutch fuse/slot option on the course computer is for installations including drive units other than Raymarine. If you have the fuse inserted in the 24v slot, and the drive is Raymarine, the clutch will overheat and can intermittently lock. If this is the case, the clutch will need replacing because the damage has been done.

Like I said, this is a wild guess, but sometimes you can never tell.

Bill

Hi again
It is an autohelm ST 7000 and the boatsystem and the computer is 24 volt, but i am aware that the driver "only" is 12 volt.
But anyway. The fuser for the driverunit, where is that placed, inside
the unit or ?
And thanks for you respons

Kind regards