MOTU 896. Output nr.2 not working.

[Hayman]

Anyone had this problem before?

Have not opened it up yet. Wanted to check if someone could give me a hint about what the problem could be.

Thanks

Richard

 

[Milkmansound]

I find that just turning it off and on again usually solves most of the problems, since they are firmware or software related most times. Just tonight my 896HD was flaking out, and that solved the problems. Always try the simplest thing first!

 

[Hayman]

[quote author="Milkmansound"]I find that just turning it off and on again usually solves most of the problems, since they are firmware or software related most times. Just tonight my 896HD was flaking out, and that solved the problems. Always try the simplest thing first![/quote]

Thanks, but this is a problem that has been permanent for a few months now.

I checked it today. There is a BB DRV134 line driver at every output. Before that a NJM4580 opamp.

I measured the output (with a sinewave at the input). Channel one (that is ok) is 23mV DC and 2,5V AC. The bad channel is 12,8V DC and 0,001V AC. It has a weak distorted sound.

What could this be?

Richard

 

[pucho812]

sounds like you need to replace the tube :razz: oh wait no where was I. oh yeah check and see if the op amp is getting proper voltages to run.... could be a bad opamp

 

[Hayman]

I have read that many have problems with MOTU hardware outputs and inputs going bad. The NJM4580 is a really low cost opamp and I'm thinking about replacing with OPA2406s or OPA2228s.

Richard

 

[Milkmansound]

Black Lion Audio has a kit for the 896 - I am not sure what he puts in there. Its definitely a surface mount IC - and can certainly be replaced easily with the proper tools. If that does not take care of the problem, it would probably not take much more to figure it out.

 

[pucho812]

you know I had a similar problem with a slow tools 192 and it turned out a cap had blown. But this caused more issues as not only was the audio not passing it was also causing the 192 to not turn on. Had to repalce it with digidesign...

 

[Hayman]

I was also thinking about a blown cap since I have 12V DC on the output.

The opamps on the output card are DIP8.

Richard

 

[AudioJohn]

I have repaired a few defective MOTU outputs - it is most likely to be simply the DRV134 that has failed.

They are directly coupled to the output (no capacitors) - so the application of a bit of DC - especially Phantom - will kill this chip.

I suspect that damage is often caused by the connection of an XLR cable from the mic inputs (with +48 volt Phantom switched on) - to an output by mistake.

Oops.....!

 

[Milkmansound]

good thing those 134 IC's are so easy to find...

I think its a 2-3 month wait still! Thanks TI.

 

[Hayman]

[quote author="Milkmansound"]good thing those 134 IC's are so easy to find...

I think its a 2-3 month wait still! Thanks TI.[/quote]

That is what I just found out... :shock:

 

[AudioJohn]

DRV134PA's are currently available from stock from RS Components in the UK.
Expensive though......

rswww.com

Stock code: 378-2676

 

[skipwave]

I've got a bad output channel on my 896. I'm certain that phantom was never connected to it, unless someone did that while my back was turned. If someone in the states is going to order the chips from the UK, I'd like to combine our orders and get a couple.

 

[Hayman]

[quote author="AudioJohn"]I have repaired a few defective MOTU outputs - it is most likely to be simply the DRV134 that has failed.

They are directly coupled to the output (no capacitors) - so the application of a bit of DC - especially Phantom - will kill this chip.

I suspect that damage is often caused by the connection of an XLR cable from the mic inputs (with +48 volt Phantom switched on) - to an output by mistake.

Oops.....![/quote]

Replaced the DRV134 tonight. It's working again. Thanks :razz:

Also replaced one opamp with a OPA2604. Works fine that too. :grin:

Richard

 

[James HE]

[quote author="Hayman"]
Replaced the DRV134 tonight. It's working again. Thanks :razz:

Also replaced one opamp with a OPA2604. Works fine that too. :grin:

Richard[/quote]

Do you find that this is an improvement to the sound?

 

[Hayman]

[quote author="James HE"][quote author="Hayman"]
Replaced the DRV134 tonight. It's working again. Thanks :razz:

Also replaced one opamp with a OPA2604. Works fine that too. :grin:

Richard[/quote]

Do you find that this is an improvement to the sound?[/quote]

I'll have to set up a AB test so I can switch fast between the two. Did not have the time to do that last night. All I can say for now is that I felt there was an improvement in the bass and that it sounded more open.

I'll get back with a report when I have done some more listening.

Richard