troubles with MB64

[rogic]

Hello,

we're still having troubles to make midibox64 working.

We connected CORE,LTC,DIN and AIN. We put the new max232 and 74HC00 chips on LTC - it worked again for a few moments and then nothing. First try was without AIN module, but now we added it and all unused pots were clamped to the ground. Also the second AIN input on the CORE module was clamped to the ground (we only need 1 AIN).

Voltages on the CORE and LTC checked - everything fine. PIC is ok also - firmware checked, 'to-COM' enabled.

During 'work time' a lot of random MIDI messages were sent but I noticed one value was 'proper' - I rotated one pot we connected to AIN (pot #1) and got from values 00 to 7F. Other MIDI messages are something like Contrast or Volume, etc... They appeared in 'series' - a lot of them, then a break for a second or so, then again.

DIN and AIN modules are original from Thorsten's site. All components are with original values. CORE and LTC have changes - 5V supply from external source to the J2 of CORE. Some things removed since we don't need them:

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If this can help, here are some other symptoms:

- when turned on, the sound is heard for the moment from the soundcard like there is some extra voltage running through LTC to com port... I am not sure if RS232 chip is ok, but is it possible that we have something burned because when we changed RS232 and 74HC00, MB64 worked? (for a moment) There is no sound when we connect 'dead' MB64...

- LEDs on LTC are not working at all. Not even during the 'work time'. They are connected properly. Do they have to light if COM port is used only?

- LTC module cable (from max232 to COM port) is 1.5m long (from old mouse)

If anyone have any idea how to troubleshoot this, please help.

[TK.]

Hi Nenad,

it seems that there are some weak (bad soldered) connections on your board, because the MIDIbox runs totally "uncontrolled". Ok, let's do it step by step. LCD and PIC are working - fine - so you could use the test programs provided under Concepts->MB Hardware Platform->Test Programs in order to test every module seperately. This allows you to identify the root cause(s) step by step.

Start with the AIN test program, thereafter with the button test (even if no DIN module is connected) in order to check if there are any floating inputs. I think that this already will give you some hints for the failures. Thereafter you can continue to debug the LTC --- the LEDs *must* flicker when any MIDI event is sent or received.

If the LTC has not been connected properly, the core will receive a lot of random MIDI events from the floating MIDI In input - they will be forwarded to MIDI Out by the MB64 merger --- check this by connecting the 1.2k resistor (Core:R6). Thereafter no random MIDI event will be sent anymore.

Best Regards, Thorsten.

[rogic]

Hi,

Thorsten, a big thanks for your reply. I am going nuts with this thing :(

On next monday, a friend who's an expert in electronics will be back in town and I will sit downwith him to check everything. I do not have easy access to a PIC programmer, but I will try to burn this test programs and check.

But I didn't tell you - we don'thave LCD in our configuration - how I am supposed to see results of the tests? :(

If I connect CORE directly to gameport (to omitt LTC as a possible cause of failure) do I need optocoupler?

Thanks again,

N

[rogic]

Ok, I found a gif on the site - optocoupler not needed for direct connection to gameport.

[rogic]

Ups... but if to-COM is enabled, this is different baudrate - so I can't test MB64 without LTC?

[TK.]

Hi Nenad,

I'm not sure - how did you select the to-COM option without a LCD. Did you use a patched .hex file? If not - if you've used the default firmware - your box is running with the common MIDI baudrate and this would be the reason for the random MIDI events.

Best Regards, Thorsten.

[rogic]

Hi Thorsten,

to-COM is enabled in firmware - was patched before burning.

I am not sure if you understand me properly - MB64 doesn't work at all. It only works for a few moments when I change all 3 ICs on the LTC - 232 & 74HC00.

[TK.]

Hi Nenad,

no, currently it isn't really clear enough why your circuit is failing. Do you mean that after you've changed the ICs the MIDIbox is running for some minutes, and that thereafter they are damaged so that they have to be replaced again?

In this case I would say: stop exchanging the ICs! Remove all ICs from the sockets (LTC and Core module) and measure the Vss/Vcc voltages on all sockets to ensure that the voltage level never exceeds 5V. It seems that something is wrong with your LTC module - so the main focus should be to find the root cause there. Print out the schematic and compare it with your board, check every track for short circuits, the polarity of the caps & diodes (LEDs) - this should help.

Best Regards, Thorsten.

[rogic]

Hi Thorsten

thanks very much for quick answer again. Yes, it is like that - circuit is doing something (random events are there, but I get something actually) for minute or two and then dies. Voltages on LTC are ok, but since I don't have that much experience with electronics, I' ll wait for a local guru to come back to town (monday) and check EVERYTHING with him. I'll check the contacts for all modules today myself. Other things - I'll wait for guy with more experience. I'll definately print everything today.