Autohelm 6000 Bowing a Fuse

[ErikFinn]

Originally Posted by Capn Dan

Erik,

The "NPN" is the type transistor (vs a PNP type). I can't find a datasheet for BDW398 so that may be a misprint. Any NPN, with similar ratings to the BDW93 will work. Just make sure it is a NPN.

Link to datasheet:

BDW93B Datasheet pdf - NPN Epitaxial Silicon Transistor - Fairchild Semiconductor

If you are in Malaysia, check with a local electronics repair shop (TV, radios) and they should have something that will work.

Dan

Thanks Capn Dan,
I called one electronics shop today I've visited earlier; they don't have it. I'll be searching other shops tomorrow, hopefully with better luck.

[Capn Dan]

Just ask for any NPN transistor in a TO-220 package (shape of transistor). They are also available on ebay.

[ErikFinn]

Originally Posted by Capn Dan

Erik,

The "NPN" is the type transistor (vs a PNP type). I can't find a datasheet for BDW398 so that may be a misprint. Any NPN, with similar ratings to the BDW93 will work. Just make sure it is a NPN.

Link to datasheet:

BDW93B Datasheet pdf - NPN Epitaxial Silicon Transistor - Fairchild Semiconductor

If you are in Malaysia, check with a local electronics repair shop (TV, radios) and they should have something that will work.

Dan

Managed to find one shop that had some transistors, they didn't have my BDW93B but the rep checked out some books and told that BDX33C would be equivalent, so I bought a few of those.
Now back at the boat I searched for info and the type is correctly NPN, but ratings are a bit different. I don't know if this is significant, but what say you, can I use this BDX33C or should I continue to look for something better matching with my original BDW93B ?

BDW93B Datasheet, BDW93B Equivalent, PDF Data Sheets. Parameters and Characteristics. Electronic Component Catalog

BDX33C Datasheet, BDX33C Equivalent, PDF Data Sheets. Parameters and Characteristics. Electronic Component Catalog

[Capn Dan]

Probbly OK as the original specs are for a TIP41A. Test the diode right next to the bad BDW93. Multimeter on diode, black probe at banded end, should read about 0.5.

If you have not soldered circuit boards you might consider taking the board to the shop where you bought the transistors and have them do it.

[ErikFinn]

Originally Posted by Capn Dan

Probbly OK as the original specs are for a TIP41A. Test the diode right next to the bad BDW93. Multimeter on diode, black probe at banded end, should read about 0.5.

If you have not soldered circuit boards you might consider taking the board to the shop where you bought the transistors and have them do it.

Okay, I'm starting to doubt my capability to get this thing fixed. (maybe it's just the cold I've caught, but...)

The diode right next to the BDW93B is D8 and it seems to be bad too, as I get a continuous beep from my Fluke 73 and it reads about .012.
Same thing with D11, but it reads about .084.
The other nine diodes seem to test ok, readings are about .5.

I found a company that may have my correct BDW93B here in Malaysia, I will call them tomorrow monday if they have it and if they ship.
BDW93B - MULTICOMP - DARLINGTON TRANSISTOR, TO-220 | element14 Malaysia

But if in addition to the TR, if I have diodes bad too I'm not sure what else will be bad as well.
Parts over here seem to be very difficult to find. So far I've spent two whole days following a lead after lead after lead and checked out about a dozen shops and didn't manage to find the correct TR (BDW93B). They do manufacture components over here but most if not all is exported, I was told. None of the shops solder circuit boards, but I may be able to find someone as I don't trust my skills in pcb soldering.

At this moment I would have two questions in mind:
1) In general, are transistors and diodes the most vulnerable to damage? How about the other components?
Or in other words, if I have a bad transistor and two diodes, should I expect other components to be bad as well. In which case it would probably become too difficult for me to find the bad ones, source parts, and have this computer fixed here.
2) Speculating on the cause of the presumed damage (one TR, two diodes), what may have caused this? Old age? lightning strike? Normal wear and tear?

-Erik

[Searanger50]

Hi again,
From your diagram the circuit appears to be either an amplifier or more likely a voltage stabilisation cct designed to keep the input to IC1 at a set level. TR1 is a two stage transistor amplifier. Failure of any of the components in this circuit could have caused the problem so it is important to test the diode (this looks like it is a zener diode designed to breakdown if a large reverse current is plased across it), R12 (most likely culprit as it sets the input voltage to TR1) and the smoothing capacitor C1. You will have to do this with one connection of each component disconnected. To burn out TR1 either TR1 itself failed or one of the other components will most likely show a direct short circuit.
I suggest you remove TR1 and then test the diode and the resistor (the resistance it should read can be calculated from its markings - if it has coloured bands Google Resistor Colour Code) and the diode should read infinity in one direction and a small resistance in the other BUT as it is a zener a 9V battery may be enough to trigger the reverse current breakdown so a cheap meter with a 1.5V battery may be needed. Finally disconnect one end of C1 and check it is not a direct short (Zero Ohms). If all these are ok replace TR1 and cross your fingers. If the fault still exists then IC1 is likely to be the cause but this would be very difficult to replace without more sophisticated equipment.

Hope this helps and good luck.
Kevin.

[ErikFinn]

Originally Posted by Searanger50

Hi again,
From your diagram the circuit appears to be either an amplifier or more likely a voltage stabilisation cct designed to keep the input to IC1 at a set level. TR1 is a two stage transistor amplifier. Failure of any of the components in this circuit could have caused the problem so it is important to test the diode (this looks like it is a zener diode designed to breakdown if a large reverse current is plased across it), R12 (most likely culprit as it sets the input voltage to TR1) and the smoothing capacitor C1. You will have to do this with one connection of each component disconnected. To burn out TR1 either TR1 itself failed or one of the other components will most likely show a direct short circuit.
I suggest you remove TR1 and then test the diode and the resistor (the resistance it should read can be calculated from its markings - if it has coloured bands Google Resistor Colour Code) and the diode should read infinity in one direction and a small resistance in the other BUT as it is a zener a 9V battery may be enough to trigger the reverse current breakdown so a cheap meter with a 1.5V battery may be needed. Finally disconnect one end of C1 and check it is not a direct short (Zero Ohms). If all these are ok replace TR1 and cross your fingers. If the fault still exists then IC1 is likely to be the cause but this would be very difficult to replace without more sophisticated equipment.

Hope this helps and good luck.
Kevin.

Thank you for your advice Kevin. I really know just about nil about electronics, just hoping to be lucky and get this thing fixed. The other alternative is a new course computer and a new control unit, looking at around 2'500 USD.
I have the Service Manual for the AH6000, and the D8 is listed as "Zener, BZX61C47".
R12 is listed as "22R, 5%, .25w, C'Film". When I measure it with my Fluke 73 I get about 22.6 ohms. This with the R12 resistor in place on the pcb and the Fluke set to ohms; is this a NOT acceptable method to measure?
So far I have not disconnected any of the components. I'm afraid to touch the pcb with the soldering iron as afraid I would toast the thing. You say I should disconnect TR1, R12, D8, and C1 each and then to measure them individually?
My Fluke 73 appears to have a 9V battery; you say I should use another multimeter which uses a 1,5V battery when testing transistors and diodes?
Also, how do I set my multimeter to check the C1? Fluke set to ohms?
When I've tested the transistors and the diodes I've used the Fluke with the selector set to diode selection.

[ErikFinn]

Originally Posted by Searanger50

Hi again,
From your diagram the circuit appears to be either an amplifier or more likely a voltage stabilisation cct designed to keep the input to IC1 at a set level.

You were correct about this circuit; I was browsing the Service Manual in my effort in trying to understand more and this caught my attention; "TR1, D8 and R12 form a line spike catcher. TR1 switches on when when the input voltage exceeds 48V."

[Teknav]

I think that you'll need a new board. If you only replace the burned components, you'll be back at where you started. I wish I had a better solution for you. Mauritz

[DeepFrz]

If you are in a marina perhaps you can find a ham radio operator who has also done some experimenting in his career. I'm sure its getting harder and harder to find any one with soldering skills in the general population.

[ErikFinn]

Originally Posted by Teknav

I think that you'll need a new board. If you only replace the burned components, you'll be back at where you started. I wish I had a better solution for you. Mauritz

Yes, that would be nice, but spares are no longer available from Raymarine. A new SPX-10 Computer and a new control unit would be around 2'500 USD. So that's my incentive in trying to get this old one fixed if possible...

[ErikFinn]

Originally Posted by DeepFrz

If you are in a marina perhaps you can find a ham radio operator who has also done some experimenting in his career. I'm sure its getting harder and harder to find any one with soldering skills in the general population.

Thanks DeepFrz, as a matter fact my neighbor who is a radio amateur recommended trying to find a "clever guy" but he didn't include himself in that group...

[Teknav]

Erik...would you please re-identify this troubling board with all the markings on it, including the unit's model/make. Maybe, someone can help you out or re-launch a new internet search! Mauritz

[Capn Dan]

Erik,

Just pull the bad transistor and diode and do not replace. Now try powering up the computer. If you have no other problem on the board, the control head will display. If it works, replace the bad diode and transistor.

Dan

[ErikFinn]

Originally Posted by Teknav

Erik...would you please re-identify this troubling board with all the markings on it, including the unit's model/make. Maybe, someone can help you out or re-launch a new internet search! Mauritz

Sure Mauritz,

this is an Autohelm 6000 Type 2 12 Volt Course Computer (Z051).
The circuit board is M061 Type 2 Course Computer PCB.

-Erik