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where do i start trouble shooting?


syamajala
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I finished the CS for my fm, but it no longer turns on. The core and the opl3 module where working fine before I hooked up the lcd, din, and dout boards. So, where should I start looking? One thing I should mention, is that although I hooked up the din and dout boards, I didn't put in the shift registers yet. I thought that I would upload the proper application to the core before I put them in. Could that be the reason?

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nope, not stuffing the boards shouldn't change anything.

you could start with checking where the problem is, eg disconnecting the boards and check the resistance between 5V and gnd. seems like a short somewhere. if a board is ok you could connect it again (one board at a time) and see if everything stays alright.

on the lcd there's not much to solder, so you could probably spot a short visually very easy, if there is one.

edit: maybe first make sure the lcd works, then the individual dins and douts. if these are alright maybe there's something wrong with the cs wiring

Edited by rosch
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It is the lcd. I disconnected the din and dout, then tried to turn it on the fm again, and it still wasn't working. I disconnected the lcd and it started working. I used SIL connectors for the lcd and soldered everything else. I think I'm going to get rid of the SILs. I'm not completely sure if I hooked up the lcd correctly. I'm using an optrex C-51850NFJ-SLW-ADN. According to the manual, pins 1, 2, 3 are Vss (gnd), Vcc (supply for logic), and Vee (supply for lcd drive). I hooked up Vss to Vs on the core, Vee to Vo, and Vcc to Vd.

Another thing is I'm not sure if I should use +5v or +!2v to power the lcd. The manual says the absolute maximum Vee should be is 13.5v, and the recommend range is between 4.4 and 5.2v. However, I'm not sure if I should worry about current. I built a power supply using NorthernLightX's schematic, I think the transformer I used is 4A, the 7805 is 1A , and the 7812 is 1A, but since everything needs 5v and the opl3 is the only thing I have hooked up to the 7812 should I use 12v for the lcd? I haven't done any current measurements yet.

Edited by syamajala
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My lcd has a NT3881 chip on it. Is there anything special I need to do? I customized the source for my CS, and uploaded it but still haven't stuff the din and douts. I noticed once that when I played some notes on the fm the screen would flicker, but it still has black squares and blinking cursor.

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Hi,

just two thoughts...

a) the NT3881 may not be HD44780 compatible (it would be cheapest time-wise if you could test with a proven-to-work display)

b) have you tried changing the display contrast using the contrast potentiometer?

Greets, Peter

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