Autohelm 3000

[llonen]

So I have one of these on the bench for a customer, its the older analogue compass rose version. reported problem with drive motor output. a brief examination shows a defective medium power PNP power transistor which I am having trouble identifying I dont appear able to source the service manual or circuit diagram for this. Pictures below best current guess is they are a pair of BD438

There are two BD 441
and two of these query BD438

Many thanks in advance

I can produce higher res images if this will help

[stj]

Re: Autohelm 3000

complement of BD441 is BD442

[R_J]

Re: Autohelm 3000

Not sure what you are after? both data sheets are available.
onseni list BD441 and BD442 80v 4amp NPN & PNP

[llonen]

Re: Autohelm 3000

I have both data sheets, what I am after is input on the device that I am having trouble identifying, Complementary types are BD437 and BD441 although that looks to be a 4 with a possible 3 followed by what appears to be an 8

This is the data sheet I was working to which lists several options,

[R_J]

Re: Autohelm 3000

The bd438 is rated 45 volts, I would use the BD442 rated at 80 volts, likely about the same price. I would use the higher voltage ones of the npn and the pnp
or the NPN I would use the BD441

[stj]

Re: Autohelm 3000

i would make sure what they are driving is not binding too - incase it's causing extra load.

[llonen]

Re: Autohelm 3000

I have the drive unit here on the bench for disassembly and overhaul, so on the matter of the errant device a is a BD441 and BD442 combo going to work here given that I am not entirely sure of the device (BD438 being my best guest) and general lack of service manual / or circuit diagrams being available. In the mean time I have gone ahead and ordered the parts, will have to go with best option when they turn up lol.

[stj]

Re: Autohelm 3000

are they dead - the mystery parts i mean.

[llonen]

Re: Autohelm 3000

They certainly are, well one definitively is one of the junctions is open cct as measured off the board the other I am not quite so sure about was getting odd readings in cct it does seem serviceable when removed. I am not entirely sure though. If I get time I might obtain a cheap transistor tester and see what that makes of it as I currently test with a fluke in semiconductor mode.

[llonen]

Re: Autohelm 3000

Thanking everyone for their input on this repair, so after tracing out the circuit diagram for the board and confirming that the devices were configured as complimentary pairing final device choice came down to bd 442 as per above recommendation and datasheet. Drive mechanism was stripped down was indecently tested on a current limited bench supply cleaned re greased assembled.

Complete system then tested on a current limited bench supply, and successful results.

Thank you again for your input.

[sam_sam_sam]

Re: Autohelm 3000

Very nice to hear that you got it running again
Good job