asofine

I'm about to tackle this by following the instructions here: http://www.bergvillfx.com/obcrepair.html

I can source the bulbs through Pelican, but does anybody know where I can find the transistor? I'm having a difficult time finding one online and am seeing prices ranging from $1-100+. There is obviously a difference between the parts I'm finding but I can't differentiate between them myself. Any help would be appreciated!

Here's a whole page of 'em: http://www.mouser.com/Search/Refine....nnel+fet+bs170

Help...meeeee

Thanks!

ToreB

You need the TO92 type, the first hit in the list you've linked to will do perfectly.
I've got lot's of these lying around and could send you a transistor, PM me and we'll settle a deal.
Cheers,
Tore

asofine

Thanks! PM sent.

lverheul

Old thread, but would this transistor issue explain my dim display that lights up when I switch on the rear wiper?

Cheers

ToreB

Iverheul, I have never heard about this before. I have no idea how the rear wiper could interfere with the OBC backlight circuit. Is it dim when it's not supposed to be or what? There could be some short that interfere with the PWM dimmer circuit for the dashboard lights, have you tried to turn the brightness to max?
Cheers,
Tore

lverheul

Tore, my mech also said he had not heard about this before (fortunately he will have to fix it as part of the sale agreement).

I will try and turn the backlight up te max, see what happens. To possibly counter your theory, all the gauges are not influenced at all by the rear wiper operation (as it should be...)

Will keep you posted.

Liam

drb930

I changed my transistor, and bulb display is stable and all the digits are there...
But no orange back light.

Is there any more information on the diode?
How about a wiring diagram?
Any suggestions?

ToreB

There is no schematic available for this instrument.
The diode mentioned in Mr. Streathers book is not involved in the backlight circuit. Normally will changing the transistor be sufficient. It may be time to do some measuring to ensure that it is getting the correct on/off signals. This will require some in-depth insight in the circuit.
Cheers,
Tore

drb930

I agree, but how do to accomplish that without a schematic?

Maxi_z

My display background sometimes would stay on ( but without anything displayed ) when the car off and parked but when running it works perfectly

Could that also be related to the transistor or could it be something as a not correctly retrofitted old alarm system ?

ToreB

Maxi-z, this is a typical failed backlight transistor scenario.
Cheers,
Tore

PNW993

Here is a picture of my tac OBC, you can see its pretty dim (especially on the left side). I’m curious if you think this is a bulb or transistor issue. Thanks

ToreB

This looks normal to me. There is only one backlight bulb in the OBC display, and it works in your instrument.
I guess it looks dim and uneven due to the use of the super bright LED dial lights.
Cheers,
Tore

PNW993

Hi ToreB, The picture makes the dial lights look brighter than they are. They are the original OEM bulbs, not LEDs. I brightened the exposure of the image so it was easier to see how uneven the OBC light looks.

ToreB

Thanks for clarifying this.
My experience is that the OBC LCD backlight is varying from instrument to instrument, some are a bit darker than others, and some are a bit uneven in light distribution.
It could help to change the bulb, but this is by no means a fault in the electronics.
Cheers,
Tore