MOTU 896 mk3 re-cap

[eum]

Re: MOTU 896 mk3 re-cap

Hi @Khron, I've been fixing some audio stuff for a little while, and been super happy to find your blog and learn more stuff about soundcards ! Thanks !

I got a cheap 896 mk3 making the "CPU not valid error, Update firmware" error. The error continues after I changed the worst caps in here, brand Meritek. Next will be the big 400V 33uF that you seemed to critisize.

I have a working Ultralite mk3, same generation, also FireWire only, and it has the same, classic, TSB41AB2. I've made all diode measurements to compare and rule out this chip. All seems good except the pins connected to AVdd/DVdd. They show 0.08V on the working Ultralite but on the 896 it starts low at 0.0x but quickly raises like when charging a cap.

My guess is that a big chip like CPU/DSP/... is disconnected from power line and so it doesn't pull down the line as it should.

Any clear insight, anyone ?

eum

[rbarrios]

Re: MOTU 896 mk3 re-cap

Old thread, new message... first post here. My 828 MK3 started arcing inside, I found a very leaky 400V cap on the power supply. I will recap the whole board.

Great info here!
Roberto
www.rbarrios.com

[Khron]

Re: MOTU 896 mk3 re-cap

What exactly does the version / revision of the power supply board have to do with anything?

Or did you not understand the list of advices?

[bavitamin]

Re: MOTU 896 mk3 re-cap

Dear Khron!
Thank you for suggested power station but it doesn't fit my sound card. My power board has marking «PS-3501» REV4.
Can I ask you for help and share power station for this version if you have it?
See the picture attached
I will be grateful for your help!

http://uzzors2k.4hv.org/projectfiles...0Converter.GIF

Except the controller and the MOSFET are an "all in one" device. I see that's not visible in the photos i've attached here, but you should be able to identify that. Googling up the datasheet for that will surely include some "typical application" schematic, which should be very similar to what's on the board.

First step, in your case, would be to see if the power supply puts out the voltages it's supposed to. Fortunately, that's really easy, on that little connection-board between the PSU board and the main board.

I'd start with using the continuity checker on your multimeter (aka. the "beeper"), to see which of those are the ground connections (there should be 2 or 3, if memory serves). I think the top one (toward the rear of the unit) is the 3.3v, then a 3.8v, and other than that, there should be some +/-15V (or +/- something) for supplying the opamps, and a +50v or so, for the phantom-power supply.

But even before that, see if the capacitors on the secondary are bulged - if any of them are, there's your (first) culprit Second in line would be the small "start-up" capacitor on the primary (near the switching controller+FET).

[bavitamin]

Re: MOTU 896 mk3 re-cap

Khron, you're just super!
Thank you very much for your help!
I hope this helps in resolving the issue!
Have a nice day!)

[Khron]

Re: MOTU 896 mk3 re-cap

http://uzzors2k.4hv.org/projectfiles...0Converter.GIF

Except the controller and the MOSFET are an "all in one" device. I see that's not visible in the photos i've attached here, but you should be able to identify that. Googling up the datasheet for that will surely include some "typical application" schematic, which should be very similar to what's on the board.

First step, in your case, would be to see if the power supply puts out the voltages it's supposed to. Fortunately, that's really easy, on that little connection-board between the PSU board and the main board.

I'd start with using the continuity checker on your multimeter (aka. the "beeper"), to see which of those are the ground connections (there should be 2 or 3, if memory serves). I think the top one (toward the rear of the unit) is the 3.3v, then a 3.8v, and other than that, there should be some +/-15V (or +/- something) for supplying the opamps, and a +50v or so, for the phantom-power supply.

But even before that, see if the capacitors on the secondary are bulged - if any of them are, there's your (first) culprit Second in line would be the small "start-up" capacitor on the primary (near the switching controller+FET).

[bavitamin]

Re: MOTU 896 mk3 re-cap

Hello, dear Khron!
I had a big problem - after a voltage drop my motu 896 does not turn on, but only the LEDs on the front panel flash ...
There are suggestions that the power board is out of order.
Service manuals - it is not possible to find ...
No information on the power scheme, I also can not find ...
With great joy and hope, I met this forum, where I very much hope to get help!
Very much I ask you about support!
Can you please tell me if you have a service manual for this device?
If not, then maybe you can tell how the power scheme is arranged?
I would really appreciate any help!
Thank you so much!)

[Khron]

Re: MOTU 896 mk3 re-cap

I'm willing to bet good money you can't get any such detailed information from... anywhere, really. Not from the internet, and deffo not from MOTU themselves.

One first step you can take is to separate as many sub-parts from the mainboard as possible (in order to ease the tracking down of the issue). As in, disconnecting the top (output) board, as well as the front panel. If that 5v short goes away, you can then conclude the issue is on one of those boards; otherwise, it's on the mainboard.

That being said though, i'm wondering how many / which components on the mainboard are actually supplied from 5v. Some of the converters, i'd guess, may use 5v for the analog supplies (you'll wanna check the respective datasheets, to make sure). Most of the digital stuff will be supplied from a 3.3v rail (which i believe comes straight from the power supply).

In the internal photos i attached in the first post here, i noticed that inverting switching regulator on the far left side of the unit, with a 7905 on its output. I'm pretty sure that provides the -5v rail for the PGA2500 mic preamps, but i don't recall where it draws power from - is it the +5v rail, i wonder?

Actually, i think it does indeed - i seem to have marked what rails the electrolytics were on, so i knew what voltage ratings to use.
https://www.badcaps.net/forum/attach...4&d=1437783248

Right next to that big cap in the lower-left corner i see an "FB33" marking - FB usually stands for "ferrite bead", which should be easy-enough to remove with a wide-tip soldering iron. Just blob on plenty of extra solder on each end, and then angle the tip so it's parallel to the component and you're able to melt the solder on both ends at once, and thus you should be able to just gently push it aside and off the pads.

But yeah, first step, separate the "daughterboards" and see if the fault persists. If it does and the issue's on the mainboard, i'd kinda-sorta expect a power-stage to have failed (that hard), rather than a "small-signal" one. Either that, or some ceramic cap might've developed some micro-cracks and developed an internal short-circuit.

https://www.youtube.com/watch?v=VwdnGbI5ls8
https://www.youtube.com/watch?v=QgKY5QWehME

----------------

<sigh> Looks like my reading skills are getting severely "rusty" - only after typing up all the stuff above, did i notice you said the short is on the INPUT of that 5v regulator.

If memory serves, that regulator gets supplied directly from a 5.5v (or so) rail straight out of the power supply, doesn't it? If that's true, it might be worth (double-) checking the rectifying diodes on the power supply's secondary side.

[gaztech]

Re: MOTU 896 mk3 re-cap

Hi Khron, I'm posting here as I can't seem to find any other relevant people that have had issues with the Motu 896 (MkIII).

I have one here that a friend gave me to fix. Said it was working then went off (this was apparently over a year ago). I took it apart and found loads of bad caps in it. Power supply wasn't working at all. However, after a re-cap session I now have the PSU up and running and I also replaced a load of 1000uF caps on the main board too. After finishing up with the replacements I put it back together and turned it on. Power supply, as I said is now ok but the unit still won't come on - at least it doesn't light up. However, I do hear the output relays clicking in upon turn-on so something is happening.

Further investigation reveals a short on the REG1 input pins (PS79650 5v regulator). This probably accounts for the "non-turnon" state but I really don't want to have to start chasing this short all over the main board as it might involve lifting components and breaking tracks! What I *really need* is a schematic in order to trace this. I know you don't have one but I don't know how much in-depth knowledge you have of this unit and whether you can point me in the right direction. Maybe you have come across this fault before?

Anyone reading this... do you have a schematic you can share to help me out with this? Or, has anyone encountered this fault before? Any input anyone can give me will help, otherwise this is going to be a very delicate operation.

Any advice would be useful. Thank you.

[Khron]

Re: MOTU 896 mk3 re-cap

Try THIS.

[jocondor]

Re: MOTU 896 mk3 re-cap

* FiNLand

I haven't seen any myself (knock on wood ), "only" squirrels, hares (ie. BIG wild rabbits) and the occasional deer/moose.

Is Finland a nice country ? is it easy to chain ladies over there? Is it cold?

what average hair colour have ladies over?

[Khron]

Re: MOTU 896 mk3 re-cap

* FiNLand

I haven't seen any myself (knock on wood ), "only" squirrels, hares (ie. BIG wild rabbits) and the occasional deer/moose.

[jocondor]

Re: MOTU 896 mk3 re-cap

only russian ones probably.

Here in Italy we have some ....in North and center side....and you where are you based?

[stj]

Re: MOTU 896 mk3 re-cap

only russian ones probably.

[jocondor]

Re: MOTU 896 mk3 re-cap

do you have bears in the forests of Filland Khron?

[jocondor]

Re: MOTU 896 mk3 re-cap

Hi Khron I confess you I really would like to visit your country ...I will do it one day maybe...hence are the two CS5368 the ADC for the frontal 8 input channels? I guess it....so why am I so concerned with such detail ?? Just why I have to do servicing very soon in to gears like that

[Khron]

Re: MOTU 896 mk3 re-cap

It's the first of March, so "obviously" it's nice & wintery

CS5368 - see my first post. they're the ADC's, so... odds are pretty good they play the role of converting the analog input signals into digital ones Shocking, i know :P

Umm... Technically, the encoders are the one doing the controlling If they had motors attached to them, THEN they would be the devices that are being controlled Going by what i can see in the last picture in the 2nd post, that pin header's likely connected to that 74-series chip next to it (which i'm guessing, does some serial-to-parallel converting for the LCD & leds), which then goes into the Xilinx FPGA. I wouldn't be surprised if the encoders were multiplexed by some chip(s) on the front panel board, and then go straight into the FPGA (if not even the Atmel chip).

May i ask why you're so concerned with such details (which aren't really involved in the sound aspect)?

[jocondor]

Re: MOTU 896 mk3 re-cap

Ok Khron thanks ...what's the weather and the temperature in Finland in these days? ..back to 896, can you tell me the role or the IC's CS 5368? They seem to be A/D converter, moreover what are the IC's which control the 8 input gain enconders ? And the IC's which drive the leds S/meter?

[Khron]

Re: MOTU 896 mk3 re-cap

See for yourself:

https://www.badcaps.net/forum/attach...4&d=1437783248

Actually, now that i take a closer look at that picture, the writing on those looks more similar to the ST ones that are ahead of ADC's - TS922.

I have no idea about the exact role of those opamps, i haven't bothered tracing out the circuit And regarding the relays, that's most likely.

[jocondor]

Re: MOTU 896 mk3 re-cap

In the last photo attached to post #2, i can see there are a pair of opamps (possibly 4580's) between each input XLR and the row of relays.

What do i think about those? They're expensive

1) http://nwavguy.blogspot.fi/2011/08/o...ths-facts.html
2) http://nwavguy.blogspot.fi/2011/08/o...surements.html

The 4-pin devices are bridge rectifiers. In this case, they're used as diode clamps.

https://www.gearslutz.com/board/atta...a217-large.gif

Thanks once again for further answer ..ok do you confirm there is an op amp possibly the 4580 prior the PGA2000 in each channel ? What is its own purpose to amp the audio signal before the PGA2000? Moreover what is the function of the row of relays to select pad function and to enable the phantom power?