megadrum and midi port: no sound!

[dmitri]

Also read this about LCD problems: http://www.megadrum.info/forums/viewtopic.php?f=3&t=492

[ubaid88]

Hey dmitri I was also not not getting backlight. So I swapped. Pin 15 and 16. And i got it. Although everything to digital board was connected properly. And there was no shorts or bad wiring.

[lidel]

inverted pin 15 and 16, megadrum don't work. lcd screen is black, no light

[dmitri]

inverted pin 15 and 16, megadrum don't work. lcd screen is black, no light

You don't need to swap wires for pins 15 and 16, it is obvious that the back light on your LCD is working fine.

[Ken Forgettable]

inverted pin 15 and 16, megadrum don't work. lcd screen is black, no light

First get your (blue) backlight working again...

Now, maybe your PC is not set up correctly? Try using MIDIOX. Set the MIDI input to the Megadrum and watch for MIDI activity - if there is any you need to configure your PC software again to produce the sounds as in this case, your brain is working fine.

this is the problem. sorry for the picture. as you can see the lcd doesn't show nothing. what can be the reason?

This is by far the worst picture of a LCD I have ever seen but shows Megadrum working ... I think.

LCD backlights have nothing to do with the image display as such, they just serve to illuminate the display as a whole. It's quite common for a laptop inverter to fail and not deliver the high voltage required to energise a functioning florescent backlight. Using a torch will usually show the display itself is fully functional – these unfortunates need to scavenge a new invertor.

Megadrum can adjust its LCD contrast voltage within certain limits by pressing UP/Down on the copyright page of the Menu. It does this in a rather peculiar way, essentially by sticking a duty cycle via a voltage divider and smoothing cap which is tapped off into the contrast input (pin 3). This contrast voltage adjustment is *only* for the character display, controlling how much the liquid crystal will polorize (ie block) the light from the observer.

Most people will expect the contrast of D.Skachkov to vary from being high to being faint – I know I do; but if an LCD shows blocks where the characters should be then the contrast voltage range contrrolled by Megadrum (for the particular LCD you have) may not be in spec' – probabally not be enough spunk to flip the juice within the character cell itself.

LCD.gif

The third image illustrates a synthex v2.8 white on blue that had too little voltage on the LCD contrast input (pin 3). Rather than mod' the board (ie reduce R24) I stuck a 270 ohm resistor between Pin 1 and 3 of the LCD – there was no firmware fault.

PS. The last few bootloaders can sometimes leave the LCD totally blank – in these cases you can coax it into life by cycling through the crystal speeds.

[lidel]

my lcd problem is the number3. it doesn't work. i'm going crazy

[dmitri]

my lcd problem is the number3. it doesn't work. i'm going crazy

Since you gave very little description, I'm tempted to ask how you came to this conclusion...Anyway, in the step 2 it says:

If you adjust the contrast from the firmware (blindly, since the data communication between Atmega and the LCD is presumably broken, by pressing LEFT for a few seconds to guarantee you're in the first point of the menu and then pressing UP/DOWN) but still not able to see black boxes, than either the LCD is faulty or Atmega is not working properly. In that case temporarily connect pin 3 of the LCD to pin 1 ground. DON'T ACCIDENTALLY CONNECT pins 1 and 2 of the LCD - you may damage USB port or power supply. When you connect pin 3 of the LCD to the ground you set LCD contrast to the maximum and black boxes in the top raw should stand out straight away. If they don't, your LCD is faulty. If they do, your Atmega is not working properly.

Did you follow this? What were your results? And, please, include as many details as possible (see http://www.megadrum.info/forums/viewtopic.php?f=3&t=352).

[lidel]

updating firmware is impossible, i follow the instructions and i hav "error trying to send the sysex file". tensions are correct ( used a tester with the parametres found in this forum). if my lcd screen or atmega is boken where can i buy? do you need other infos? the procedure to test the lcd will be done in these days

[dmitri]

updating firmware is impossible, i follow the instructions and i hav "error trying to send the sysex file". tensions are correct ( used a tester with the parametres found in this forum).

Try this http://www.megadrum.info/forums/viewtopic.php?f=3&t=622 but since you didn't sort the LCD problem you'll have to do it blindly.

if my lcd screen or atmega is boken where can i buy? do you need other infos? the procedure to test the lcd will be done in these days

If you're to buy new components then these are directions: http://www.megadrum.info/content/buying-components . You'll have to program Atmega yourself.

What procedure are you planning to do to test the LCD?