Autohelm 6000 Bowing a Fuse

[Capn Dan]

Yes, that's it. There are two circuit boards in the box. The one attached to the terminal box is the "computer" and the long one is the power amp board. The problem is most likely in the "computer" board. You can look for burned components or if you have some electrical experience, start testing components.

[ErikFinn]

Ok, good, actually there was something I noticed last week already on one of the components and the whole casing smelled a bit, hmm, funny, but with my very limited knowledge about electronics I couldn't say if was normal or not. I'll post a picture again tomorrow.

[Teknav]

Smell the board for a very distinct odor; electronics components when fried give off a "phenolic" smell. See if any component on the board is charred, broken, crossed over/touching another component, or has a build-up of salt on it (due to a leakage). Replace, if that's the case; you may also need to examine the entire module for other issues. Mauritz

[ErikFinn]

Visually looking at the computer pcb (haven't looked at the power amplifier pcb yet):
the "TR1" looks like a suspect; the whole component looks "older" than the other ones, the lettering looks faded, and it just doesn't look as good as the others. LOL, not very scientific appraisal, but I'm really out of my field of knowledge with this one! Also the smell does seem to originate from this component. More pics to follow.

[ErikFinn]

from top:

[ErikFinn]

Another one top:

[Capn Dan]

If you have a very strong burned smell, you will probably be able to see a burned component. You should look at the power amp board. You must remove the 4 transistors located on the top outside of the case. Number them prior to removing as the need to go back in the same location that they were removed as there are two types.

How to test transistors can easily be found on youtube

[ErikFinn]

under pcb:

[ErikFinn]

Under TR1:

[ErikFinn]

Originally Posted by Capn Dan

If you have a very strong burned smell, you will probably be able to see a burned component. You should look at the power amp board. You must remove the 4 transistors located on the top outside of the case. Number them prior to removing as the need to go back in the same location that they were removed as there are two types.

How to test transistors can easily be found on youtube

Thanks Capn Dan, yes, this one certainly doesn't look or smell like a good one. I'll look at the PowerAmp pcb as well.
-Erik

[ErikFinn]

I did the diode testing with the TR1 on the pcb and when connecting the probes to any two of three pins I get nearly zero reading and the DMM sounds a continuous beep - I don't have the manual for the DMM but I believe this means the transistor is shorted.
Also realized what the smell reminds me of; exactly like a burning plastic or car tire.
Diode tested the Power Amplifier pcb (the other pcb inside the course computer) transistors and they all appear to be ok.
So I suppose I now need to find the part and think if I'll dare to try soldering or try to find some clever guy here in Malaysia with pcb soldering skills.

[ErikFinn]

Something caught my attention and I need to ask for advice.
I looked at my "Autohelm 6000 Service Manual" and the TR1 listed for my Z051 Course computer is "NPNBDW398".
However, looking at my pics on posts #20 & #21 the TR1 has the print on it: "SGS 28737 BDW93B".
To me these don't seem like identical parts or am I wrong?

See pic from the Service Manual under "7.5 AH 6000 TYPE CR COMPUTER PCB (Z051,Z052, Z062, Z063)" - page 76 part number listing:

Noticed on the Service Manual pcb circuit diagram the TR1 however seems to be labeled as "BDW93B" (the old photocopy quality is poor)

Is this just a case of different part numbering standards?
What's the explanation? Same part different names, or do I have a wrong part on the pcb, or is my service manual incorrect?
When I hunt for the part which part number should I ask for?
-Erik

[Searanger50]

[I][I did the diode testing with the TR1 on the pcb and when connecting the probes to any two of three pins I get nearly zero reading and the DMM sounds a continuous beep - I don't have the manual for the DMM but I believe this means the transistor is shorted./I]

You will probably have to remove / disconnect the transistor to perform this test to prevent measuring via other components in the cct.

[ErikFinn]

Originally Posted by Searanger50

You will probably have to remove / disconnect the transistor to perform this test to prevent measuring via other components in the cct.

Thanks Searanger, this is true. However, based on the smell, the looks, and the measurements taken compared with any other transistor I'm 99% confident the TR1 is shorted.
On today's agenda I have the question about the correct part number as per my previous post..

[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