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the beginnings of a fm


syamajala

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Err whad ya grab that freaky LCD for? :-\

I assume you connected it to the 12V ground, not -12V?

That 12V supply is really meant to stay nice and clean for the audio output anyway... But aside from that, I wouldn't have thought that the LCD should draw that much juice. if you put your meter in series with it, how much current is the backlight drawing? Seeing as it's just that backlight, it shouldn't be enough to overheat the 7812, so maybe there's a short somewhere, or the backlight is dead... I dunno. How much current does it draw if you disconnect everything from the LCD and just connect the backlight? Same as the above?

Oh - how are you splitting up the 12V to the LCD and OPL board? in series or parallel (a spot of ascii art might help here)

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  • 1 year later...

I decided to start working on this project again.

They are connected in parallel.

The lcd backlight draws more than 1 amp of current when its on. I think I need a current limiting resistor in series with the backlight right? When I disconnect the lcd backlight the 7812 doesn't get hot.

Now time to figure out whats wrong with the sound. I've started working in a physics lab at school that has this really neat soldering iron that looks kinda like a pair of needle nose pliers for soldering ics, that would probably help with getting some opl chipsets to test. That was the most frustrating part of this project and why i stopped working on it. 

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I decided to start working on this project again.

They are connected in parallel.

The lcd backlight draws more than 1 amp of current when its on. I think I need a current limiting resistor in series with the backlight right? When I disconnect the lcd backlight the 7812 doesn't get hot.

Why 12volts to the LCD module ?

If you see scheme of MBHP Core , you see only +5V and gnd connections, right?

Your comments about more than 1 amp of the LCD backlight current sounds : all is not so good.

You need against  checked every connection to the LCD module .

Regards, Janis

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if i remember correctly thats what the datasheet for the lcd said the backlight needed. I don't have it anymore and am trying to find it online, but there isn't a lot written on the lcd. i hope i can use this because i have 2 more just like it.

  If you returned to the scheme MBHP_CORE_V3 to the connector J15, will see pins in the two columns. Right sizes first 2 upside pins are marked : B+ , B-. These pins supply voltage "+" and "-" polarity ( or need suplly voltage ) to the yours LCD backlight pins.

I have  simpler this part of the scheme with only one 10E resistor , but its not so important.

Regards, Janis

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it looks like i messed up the opl3 and yac512. I tried replacing the op amps but still didn't hear anything. i also tried powering the lcd backlight from the 7805 and even that got hot. I need to get some more sound cards. I have 1 more pair of chips, but if i mess those up i'm out. anyway it should be fairly easy to get at them now that i have access to a nice iron.

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  • 2 weeks later...

Now that i am using the proper method desoldering smd chips is easy and i can generally do it in a matter of minutes. I used a method similar to the chip quick method but with regular solder and a desoldering iron with a bulb. i haven't tested out the chips i took off yet, but they didn't get as hot as they normally do when i desolder them, so hopefully they will work.

i also decided to get a new lcd, because i wanna make my fm look cool. I'm gonna try and go with a blue and white scheme, so i got an lcd with a blue backlight and white text, and some blue and what should be white leds.

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