Yamaha O2R - No AD-conversion

[fnninns]

You can call tech support at Yamaha and get help.
If you get a live tech they can give you pointers.
I know this because I have talked to them about 01V issues in the last 5 years.

One thing to look for is if the grounding of the boards is good.
I learned that on an 01V the CPU board derives it's ground reference via the screws that bolt it down to the metal frame.
If these get loose the 5V rails sag pretty quick because the ground reference is gone.

Since the 02Rs were designed and built in the same era as the 01V I would look for this first.
Make sure all of the screws that hold the boards in place are tight.

In the case of an 01V the Yamaha tech told me to solder a wire to the CPU's ground plane at a big trace and secure the other end to the console's frame (the GND traces are almost always the biggest traces on the board.)
I used a 12 ga.wire with an eyelet on one end and bare ware soldered to the CPU's GND plane.

If this isn't the problem and you actually need a new board you need to jump at any chance to get one. They are going to be rare.

[johnnyv]

Yes good advice, I own a 01v, there is also a issue with the battery dieing so replace that while your have it open checking the ground.

There is a lot of information on our user group at Yahoo.

Yamaha01V : Yamaha01V

[pek]

Thanks for the tips. I don't think the board gets its ground from the
mounting screws, there are no metal on the PCB around the holes for
the screws. I hooked up a scope and can see that the analog signal
goes into the ADCs and that the ADC has clock. However, VA- (negative
analog power) is 0.8V instead of -5V. All other supplies (VA+, VL+,
VD+) look ok at +5V.

[Ike Zimbel]

Any time you see a voltage like that (0.8v instead of 5v) you should suspect a short across that supply. Regulators tend to put out about half a volt when they are protecting themselves. Look for shorted tantalum caps, or if this is SMD, you should also look for shorted ceramic caps. Also, very occasionally, electrolytic caps will fail short.
Best,
Ike

[pek]

Originally Posted by Ike Zimbel

Any time you see a voltage like that (0.8v instead of 5v) you should suspect a short across that supply. Regulators tend to put out about half a volt when they are protecting themselves. Look for shorted tantalum caps, or if this is SMD, you should also look for shorted ceramic caps. Also, very occasionally, electrolytic caps will fail short.

Interesting, thanks! If I disconnect the AD-board I get good -5V at
the DC-board connector that supplies the AD-board so I've narrowed it
down to something on the AD board. There are close to 30 caps between
-5V and ground on that board. Can I check them for shorts by measuring
the resistance over the caps with a multimeter on the disconnected
board or will that blow something? If I can avoid desoldering them all
that would be great (software guy; I'm liable to poke my eye out
wielding a soldering iron for too long).

[Ike Zimbel]

Well, I just had a Soundcraft Series Five with a shorted SMD cap on the Midi-Mute board. In that case, the cap had changed colour to kind of a red (ish) from overheating first. There were also some signs of heating on the circuit board. So a close visual inspection would be a good place to start. In theory, if there is a short across the 5v rail, measuring across any decoupling cap will read the same thing. In practice, if you have a good DMM, you might get lucky and see a lower reading around the shorted cap (if it is indeed a cap that failed...could be a chip or a transistor) than at the other end of the board.
WRT poking your eye out with your soldering iron: Try turning it around. The hot, pointy end goes towards the little colourful thingees on the circuit board! ;-)
Cheers,
Ike

[pek]

Originally Posted by Ike Zimbel

Well, I just had a Soundcraft Series Five
with a shorted SMD cap on the Midi-Mute board. In that case, the cap
had changed colour to kind of a red (ish) from overheating
first. There were also some signs of heating on the circuit board. So
a close visual inspection would be a good place to start.

I can see no discoloring or bulging of any of the components on
the board or the board itself, however...

Originally Posted by Ike Zimbel

In theory, if there is a short across the
5v rail, measuring across any decoupling cap will read the same thing.

*slaps forehead* Of course, stupid of me. But this proves the short
theory wrong because there's significant resistance over a randomly
picked decoupling cap for the -5V. Back to the
impossibly-slow-to-render-pdf schematic...

Originally Posted by Ike Zimbel

WRT poking your eye out with your soldering
iron: Try turning it around. The hot, pointy end goes towards the
little colourful thingees on the circuit board! ;-)

I did wonder if the smell of burning flesh was normal...

[pek]

One other possibility (other than an ADC being bad) may be the
"LC Filter", a "LS MT Y223NB" for which I cannot find a data sheet.
It has three pins and is connected to ground and -5V "in" and "out".
Does anyone know what the specs are and how I can test it?

[ktf]

I can't remember all the faults that occurred when the three pin power molex on the converter board gives up (5v), I just remember repairing probably 20
o2r's by pulling the board and replacing the molex and it's mate. Very common problem. It gets crispy/hot and goes open. It's located toward the center of the board and it's hard to see because it's covered with ribbons.

[pek]

Originally Posted by ktf

I can't remember all the faults that occurred when
the three pin power molex on the converter board gives up (5v), I just
remember repairing probably 20 o2r's by pulling the board and
replacing the molex and it's mate. Very common problem. It gets
crispy/hot and goes open. It's located toward the center of the board
and it's hard to see because it's covered with ribbons.

Thanks for the tip. I've looked at this connector and it does not look
burnt or anything like that. I've not removed the DC board to look
underneath, but since I have good +5V (and good -5V when the AD board
is disconnected) I'm not sure if that connector is a likely source of
the problem?

[Radardoug]

I had this problem in mine, but its a bigger connector than 3 pin, maybe 5 pin, and isn't it one coming from the power transformer?

[pek]

I measured the resistance over the +5V and -5V pins on the supply to
the ADC board and got about 2M Ohms. I then put a 1.5M Ohm and a 3M
Ohm resistor over the same pins coming from the DC-board and measured
the voltage over them and in both cases it stayed at 10V so my amateur
conclusion is that the supply is ok and that the problem is really on
the ADC board itself. I'm desoldering the ADCs one by one in the hope
that one of them is bad. If this doesn't pan out I guess I'll have to
start removing the -5V to ground caps.

[Ike Zimbel]

Me, I'd do the caps first! Fewer pins, and more likely to be the failure point.
Best,
Ike

[pek]

Originally Posted by Ike Zimbel

Me, I'd do the caps first! Fewer pins, and more likely to be the failure point.
Best,
Ike

Thanks, perhaps I should. It's just that I can't really square the observed behaviour with a bad cap given that -5V and ground are not shorted?

[pek]

Success! After removing all the ADCs, getting good -5V, remounting one
ADC and getting bad -5V I finally plucked up the courage to remove the
DC-board. It turns out that it has three -5V regulators which
somehow work together with three +5V regulators. Looking underneath the
board it was a bit burnt around the soldering for all the voltage
regulators, but I could fool myself into thinking that the burns were
slightly worse around the six +5V/-5V regulators so I replaced those,
together with their decoupling caps, and that did the trick!

Thanks for all the advice guys.

[Ike Zimbel]

Nice one!