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jmamma / MegaCommand_Design

MegaCommand MIDI Controller
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Trouble with sram test and unit not working #19

Open defalutz opened 3 years ago

defalutz commented 3 years ago

Hi, i have a unit that has given me a lot of headache, Sold it to a guy who cotacted me since he had trouble. It was working perfect when unit was tested here, and then i sent it. He contacted me, long story short but said he had "sd card error" message.

I got it back, saw that the arduino board had just about got unstuck so i put it back in place properly, also put a distance between the ard board and the lid som it was locked into place. Unit worked fine afaik.

Ok, got the same email again, decided i will have a look again and will let him buy it back after a while. But when i get it i have "sd card error" when i boot it up. Just in case i reinstall latest firmware (whch is one step later than before). Boot it, everything works. Shut it down. Boot it. "Sd card error."

Weird, right?

I try a tip i read somewhere, test the voltage and ground, and all the IC circuits have 4.98 or 4.99volt in the right places, and 3.3 volt where it should be.

Ok, so i decide to run the test firmwares. The SD card firmware runs without ANY problems. Also the screen flashes black/white Buttons work great. Midi i decide not to bother with. But the i try the sram test firmware nd all i get is this:

"Megacommand SRAM test 2200"

.. and nore more.. And that´s all. Tried a lot of things, reflowed solder joints and so on and forth, even got so far as to order replacement SRAMs. Managed to desolder the old pretty niceliy.. Result? the S A M E!

Now i test with other units i am building, one so far has been tested this way (it´s missing screen, 9v switch, knobs and stuff, leds and resistors for leds, but should work the the testst i want to run. Ir runs great on the ones i used before but get the same result for SRAM test, 2200 and then STOP.

What the heck am i doing wrong? Any ideas? I have never had any customer get this issue before and i have built a LOT of MCL´s for people...

defalutz commented 3 years ago

Oh, forgot to mention; now the unit that i had the initial problem with dont display anything on the OLED, even if i install the new firmware via xloader, it´s just black. And it worked fine before, i havend done eny desolering of just this part. Thanks!

defalutz commented 3 years ago

The issue is weird; i have a short on the resistor arrrays, on the third pair from the top, ics3 and ics7. The only pair that´s supposed to be connected is the lowest pair furthest away from the midi ports.

Also, both these two joints (ics3 / 7) also beeps when i connect to pot 1, 2 and 4 and the top leg "b". Very weird! All i can think iof is that the PCB is wrecked. Anone with any ideas? I would like to try to bypass in some way but not sure how. I have dessoldered the resistor networks and still have the same issue..