Midisport Uno Problems

[brokuno]

In an effort to reduce SPAM, until your post count reaches 5, any posts that contain links (URL's) will require moderator approval.

I have 5 posts, but am still unable to post the link to m-audio tech support.

MODERATORS: If you are not going to let customers post the link, maybe you can do it yourself?

[KellyB]

Gave up on waiting for new driver for Uno for Vista SP1. Purchased a Yamaha UX16 midi-usb interface - downloaded driver straight off Yamaha website - I'm back in business. Good luck to you all...

[Asterion]

I just get random stuff: patch changes, a few notes here and there – I'm using it with Reaper on OS X. The stupidest thing is that I'm using an older Midiman keyboard – the thing is incompatible with their own stuff. Guess it's going back to the store tomorrow.

[Asterion]

Okay, so the Uno didn't work, but the 1x1 does. Go figure. Save yourself some grief and go with the 1x1.

[steve b]

Just thought I would post a recommendation to not buy this. Just returned it to Radio Shack. The midi leds never lit up, USB led flashed continuously.. Installed and uninstalled newest drivers from m-audio. I attempted to use this for a digitech gnx3 guitar processor. Installed and uninstalled the Genedit software for the digitech. Tried to plug and play, installed driver from included cd, uninstalled and installed XP, XPSP2, XPSP3 drivers from m-audio support before I finally believed what you guys already knew. Also tried different procedures from digitech website. This was a highly recommended interface by the digitech user forum till lately. Spent a good couple hours with this, how aggravating !!!!!!!

[JA]

We have identified a defect in a manufacturing run of the Midisport Uno's that is distorting the MIDI input. Please see this thread: http://forums.m-audio.com/announcement.php?f=10

[dougb]

Hi,

I just bought my first M-Audio product and it was one of the defective Midisport UNOs (bummer). Before I found JA's post about the defect I had already cracked mine open and fixed it. So, for anybody who is interested, here's the scoop.

The eight pin chip on the UNO's circuit board labeled U2 is the optocoupler that takes current pulses from your MIDI device and turns them into voltage pulses that are decoded by U1 and sent to the computer via USB. The optocoupler in the defective UNOs is a 6N138. The problem is one of two things (depending on M-Audio's original design). Either, the factory installed the wrong optocoupler (which is likely because the 6N138 is not a very good choice for a MIDI input), or M-Audio forgot to connect pin 7 of the optocoupler to ground with a resistor (which means the optocoupler's output turns on fast, but takes way too long to turn off, effectively causing it to miss pulses).

So, you've got a defective UNO with the wrong opto and it's missing a resistor (but you've got a soldering iron and a do-it-yourself attitude), what's the solution? If you solder a 5k ohm resistor from pin 7 to pin 5 on the optocoupler (6N138, U2), your MIDI input should spring to life. Adding this resistor provides a discharge path for the parasitic capacitance on the base of the output transistor in the darlington pair. Discharging the base through a resistor gets the output transistor turned off fast (no missed pulses). I added a 5k ohm resistor to mine and now it works great. Like I mentioned, the 6N138 is not a good choice for MIDI. It is a slow device with a high CTR, while MIDI (5mA input, 31250 baud, low output current) really screams for a fast device with a low CTR, but I used an oscilloscope to verify the output of the opto with a 5k ohm base resistor and it looks great.

Extra credit: While troubleshooting the MIDI input I also noticed that the leakage current of my keyboard's MIDI output was still enough to keep the input diode of the optocoupler turned on (slightly). It was not on enough to cause a problem on the output, but it sure wasn't off. This problem can be solved by soldering a 10k ohm resistor in parallel with the input diode (i.e. from pin 2 to pin 3 of U2). This resistor provides a path around the input diode for leakage currents up to 100 microamps (without developing the 1V forward voltage required to turn on the input diode).

Summary:
Solder a 5k ohm resistor from pin 7 to pin 5 on chip U2. Optionally, solder a 10k resistor from pin 2 to pin 3 on U2.

Or, follow the manufacturer's instructions and return it to your dealer/retailer.

- Doug

[apefist]

edited due to my oversight...sorry to make you look!

Here's a cool car to look at since you're already here:

[nothingworks]

Thanks. But after 2 months of hair pulling, a recall only puts my mind at ease. What I thought was user error on my part turns out to be a faulty product that simply doesn't work. I have been ripped off and I am out of 50 bucks. I cannot return the product without the plastic it came in and I will never buy any maudio again.

[mrgarth]

I am writing to report that Doug B's solution for the defective Uno works like a charm. I went to my local electronics shop and bought two resistors. They did not specifically have 5k ohm resistors; I had to choose between 4.7k and 5.6k so I chose the 4.7k ones. Total cost: about $4. I already own a soldering iron and small screwdriver, I'm not an electronics expert but I have repaired a cable or two from time to time.

It was really as simple as Doug says:

1. crack open the case with a fine tip screwdriver

2. identify the correct pins on the U2 chip. In the photo of the top of the board, you can see the black dot on the U2 chip; that is beside pin #1 and then the pins number counterclockwise around the chip (viewed from above).

3. solder the resistors on. Resistors are reversible so it doesn't matter which way they are oriented. I soldered mine to the back of the board because there was more room there. I also trimmed off about half of the leads on the resistors to make them a little smaller.

Now the Uno works perfectly. Before I did this I was having the same trouble as everyone else - the Uno was delivering a mass of garbled garbage command to my iMac from my Pioneer DJM-700 mixer, which is MIDI-enabled. Now I can seamlessly control Ableton, Serato, whatever.

See photos: