MSA-R Communication Problem

[Robert Evans]

I'm having a similar problem with communication to MSA-R as is posted to "MSA-P MIDI communication problems". The MSA LEDs light properly. I am using a USB-MIDI cable that has an activity LED (M-AUDIO) on the midi out which lights appropriately when a test file is sent using Bome's SendSX 1.30. SW 1-4 = 1 0 0 1 for channel 10. SW 5-8 = 0 1 0 0 for note range 32 - 39 (using acoustic bass and snare). I switched the MIDI cable for pins 4 & 5 back and forth as well as IC-2 (just in case I was looking at it wrong) and I connected a MIDI out (thru) back through the USB cable to attempt detection with SendSX MIDI in. This also failed to show any signal returning to the computer or the activity LED on the M-AUDIO midi in cable. I am suspicious of IC-2 (6N135) and would have tried a replacement if I could have found one in my parts supply. Static precautions were followed but I recognize that could still be a problem but the rest of the board seems functional (5 V pwr & LEDs). I attached one of the test files I used.

[John]

Hi Robert,

Your second order has shipped--please let me know if you receive it and are still unable to get things working.

[Robert Evans]

The pre-assembled MSA-R works fine. I have carefully compared the two boards and do not find any differences (diodes backwards, etc.). I looked for possible shorts (solder bridges) and made sure there were no such connections between pads but the board still doesn't respond to midi messages. I apparently didn't assemble things as good as you but I am perplexed as to what possible differences there are. I put in the new IC-2 after being especially careful about static charges. When comparing the two boards under power I notice the 5 V regulator is especially warm on the board that I wired (more so than the board that came pre-assembled). Once again I looked for solder bridges, etc. without success.

I would like to send the board back to you for your analysis and/or correction. I am stumped as I have done a number of similar kits without such problems. Obviously I did something different?/*.+,#$

New Information:

Once again I went over all connections for possible shorts. I use an "adequate" amount of flux to insure good solder connections and this sometimes causes two pads to be swamped in flux. When I again cleaned each and every connection (between each pad) with a jewler's screwdriver, the board started to work.

I send this message as I am sure others will have similar obsessive-compulsive problems. I now have two apparently functional midi interfaces.

Although the board is apparently working properly the voltage regulator is still very hot. Would you like me to send the board back for your analysis/

R. Evans

[John]

Hi Robert, you're correct that the "hot" voltage regulator indicates a problem somewhere.

If you remove all the ICs from their sockets, does the regulator still warm up when you apply power? (Or, does the presence of one IC in particular cause the heating?)

It's not a good idea to use the board if it's consuming an unusual amount of current to operate (which is likely why the regulator is warm).

You're welcome to send the board back, but I wouldn't necessarily be able to fix the problem...