Luminance control makes small difference

[FJMSoft]

Hello, I'm trying to adjust the luminance on the core module, but turning the trimpot all left or all right makes litle diference, I already changed the BC337, verified the circuit and tested the trimpot... what can be? its normal?

Thanks!

[/tilted/]

More information please...

Which make of core board?

What type of LCD?

Thanks.

[FJMSoft]

Oh sorry, I really forgot!

Its core V3

LCD HD44780

Thanks and sorry  :-[

[/tilted/]

I actually meant the make of the core board, as in: did you make the board, or buy a ready-made board and assemble it.

Also, I meant the model of LCD, but this is less relevant... they should all work.

Triple check for any wiring errors or shorts... sorry, not much else I can recommend.

Any chance of photographs??

[FJMSoft]

I made the board with the layout from here, opened in Eagle, printed and made using the toner transfer method...

I verified many times already, all connections looks ok, also tested with multimeter, changed the bc337 for another one... it gives less than 1volt from max to min adjustment.

I will try to get photographs, but dont think it will help much

[/tilted/]

could it be:

different pinout for adjustment pot?

different pinout for BC337

[FJMSoft]

Hi again Tilted...

It is very very strange... I verified eveything, the circuit, pcb, the my pcb, looked in bc337 datasheet, and looks ok!!!

But, I rotated the BC337 and now its working... for me looks inverted in every where it appears (Colector in emiter and emiter in colector)!!!!

STRANGE STRANGE STRANGE... I always worked with BC337 and used this: The chamfer facing top, pins facing me... then pins are CBE...

Well... it is now working... Thanks!

[/tilted/]

It's one of the weird things about transistors. CBE is about as likely as EBC. then there are the flat packs, which are more often BCE...

Here's a kinda useful link:

http://hamradio.lakki.iki.fi/new/Datasheets/transistor_pinouts/

[FJMSoft]

OH MY... I Cant understand... the way I put it its right to what I think, and to datasheet... but still inverted in the schematic for me!

[/tilted/]

Off hand I can't recall the specific model designations, but beware of suffix letters attached to (especially transistor) model numbers.

Sometimes you'll get something like "BC337" and "BC337A" or "BC337-D", and they might have different pinouts, for some reason...

It could also be that you have a mis-labeled of even counterfeit transistor (which isn't really much of an issue in this application).