Barco DP2K-20CLP SMPS failure, three times in four years

[Leo Enticknap]

Here's another head scratcher to join the 10S with a repeatedly failing SPG.

I have just replaced the SMPS in a DP2K-20CLP for the third time. On every occasion, the same fault has presented: the 12V output is OK, but there is no output from the 24V bus (so the cards boot up, but there is an assload of error messages covering all the fans that are supposed to be running while the lasers are off). The 24V output fuse is found to be blown, and if I replace it, the new one blows almost instantaneously as the SMPS is powered up (I see the 24V light on the FCB come on and the fans in front of the card cage turn about half a revolution after the power switch is flipped, and then they stop and the light goes out). I'm not enough of an electronics expert to be able to troubleshoot the board beyond that, but I'm told by my site contact that the venue in which this projector is operated has recently hired someone who is, and he's going to have him look over the latest SMPS to kick the bucket.

My first suspicion as to what could be causing this was bad input AC. After the second SMPS blew, we installed an MiT IS-30 spike arrestor on the power supply, but it hasn't registered any spikes thus far. Another relevant fact here is that I've also had to replace one of the LDM chassis cases twice since the projector was installed, again because its output voltage failed. These failures were on different occasions to the SMPS failures.

So this led me to wonder if the cause of these failures is actually inside the projector - maybe a fan that suddenly tries to suck way too much current? But all the fan RPMs look normal to me (both with and without the lasers lit), and in any case, disconnecting them one at a time to diagnose isn't a viable option, given that the SMPS failures only happen every 9-12 months.

The only other relevant information I can think of is that this projector is operated in a relatively hostile environment. It's in an auditorium in a theme park (not associated with a certain fictional rodent!), close to the ocean, on an open platform at the back of the auditorium, and regularly enveloped in the output from smoke machines, artificial snow, you name it. There is significant corrosion within the chassis.

Has anyone experienced these multiple SMPS failures with the same symptoms before, and/or has any idea what might be causing them? Many thanks in advance.

[Marcel Birgelen]

The only other relevant information I can think of is that this projector is operated in a relatively hostile environment. It's in an auditorium in a theme park (not associated with a certain fictional rodent!), close to the ocean, on an open platform at the back of the auditorium, and regularly enveloped in the output from smoke machines, artificial snow, you name it. There is significant corrosion within the chassis.

I'd say id you don't need DCI compatibility, for those kind of theme-park setups, you're generally much better off with some "big venue" projector from any namesake brand, as they're usually better able to cope in such harsh environments.

I've only seen once in a 4D cinema that an actual DCI projector was required, in this case, it involved some franchise from a major studio... Also, something with ice, snow and a rodent, but not THAT rodent...

I've also seen mixed used auditoriums, where a DCI projector was installed side-by-side the attraction setup. This setup did have a proper booth though. It even retained a dual interlocked DP70 setup, which was used for the original 3D movie playback.

[Steve Guttag]

I doubt it is a fan. The fuse, if it is sized properly should blow when the power supply is being asked to supply more current than it is capable of...that's the fuse's job, on an output rail. I suspect the conditions of the room, including power, may be causing your issues. Is the power on a double-conversion UPS? If not, that would be my next move. Surge arresters are for actual spikes where you don't want the occasional 270V (and up) to go dancing through the circuits. A double conversion UPS isolates the sensitive off of city power entirely.

[Leo Enticknap]

Thanks.

I'd say id you don't need DCI compatibility, for those kind of theme-park setups, you're generally much better off with some "big venue" projector from any namesake brand, as they're usually better able to cope in such harsh environments.

They don't. That projector is used to play a ten-minute 3-D novelty movie that is fed to it by unencrypted HD-SDI. I wasn't involved in the selection of projector model when it was purchased, and so do not know why a DCI projector was chosen. It could be that they wanted laser illumination specifically, and back in the late teens, that meant they had to have a DCI model. I don't know.

As for the SMPS, I'm wondering if it's a ballast on the board. If the power flow goes 240 VAC in > transform to 24V > rectify to DC > ballast to limit the output current > fuse > output, then the failure of that ballast would explain why the fuse is blowing as soon as input power is applied. But that's just a guess, and I'm hoping that the site's newly hired electronics expert can figure out which component(s) have failed, and replace them. If that could be done, they'd have a good spare for a lot less than Barco would charge for them.

I'll pass on Steve's suggestion about putting the projector on a UPS. It would need to be a big one, though, if both the lasers and the card cage were to be protected.

[Bruce Cloutier]

If there is something that presents a highly inductive load being switched on and off on the 24V bus that could be the issue. A big relay coil or heavy duty fan motor. The back EMF could be killing the regulation in the supply that then causes the fuse to blow. If you think that is the case you can add a snubber to the DC fan or whatever basically to absorb the energy when power is suddenly removed. A diode across the lines. Look up techniques for protecting relay contacts. Automotive relays all have the snubbers built-in on the coils (so your AM radio doesn't crackle and pop). That remedy can't hurt even if the problem is something else.

The other side of this are rush currents. When something is kicked on that draws way too much current from the supply, more than what its capacitors have stored, would stress the regulation. Eventually it would fail. Sometimes some 10 or 20 ohm resistors in series with the offending device can limit the rush current and protect the supply.

A small amount of incense, an ornate display of religious figures and a brief chant weekly can go a long way as preventative maintenance... sorry. ;-)

[Marcel Birgelen]

While there are quite some fans in any DP2K, none is of such size and "heft" that I'd suspect that any back EMF would be able to kill the SMPS, you'd expect the stuff in there being sufficiently over-engineered to be able to cope with that, even on the long term. Also, even though power supplies seem to be frequent ticket items in digital projectors, I'm not aware of the DP2K-20CLP being a problem child in this regards.

I'll pass on Steve's suggestion about putting the projector on a UPS. It would need to be a big one, though, if both the lasers and the card cage were to be protected.

If the incoming power really is THE problem, then a double-conversion UPS should fix it... or it might relay the problem to the UPS, but at least you've found your culprit then.
Make sure you're getting a double conversion UPS though... and yeah, if you need to put the entire projector on it, it has to be a beefy one, but you don't need much battery capacity though.

[Bruce Cloutier]

I was thinking more of a hefty relay. I will admit that I have no access to a projector so I am just guessing. I would bet tho that if you yanked the power plug on an operating projector (probably a really bad thing to do) there would be a huge ass spark.

How about a ground loop?

[Tony Bandiera Jr]

The only other relevant information I can think of is that this projector is operated in a relatively hostile environment. It's in an auditorium in a theme park (not associated with a certain fictional rodent!), close to the ocean, on an open platform at the back of the auditorium, and regularly enveloped in the output from smoke machines, artificial snow, you name it. There is significant corrosion within the chassis.

Having worked at a certain theme park in So. Cal (not the mouse, but the food) in the entertainment tech department, I can tell you for a fact that the power is extremely dirty. Lots of surges, spikes, sags, you name it. Loads of PLCs, VFDs, BVDs, CODs RSVPs and tons of motors switching on and off....plus in your case, the attraction the projector is used in having all the effects and so on operating in close electrical proximity. We were constantly repairing mixing boards, DMX controllers, dimmers and (before we switched to QSC) audio amps all the time.

You will need a solid dual conversion UPS, PLUS robust surge protection before that UPS to stop the problem from happening.

Perhaps a hush box like housing, with filtered air drawn from another space without the effects fog would be a good idea too. With the expense of that projector, even a grand or so to do that would be chump change compared to killing the projector prematurely. (We had to do that for the old CRT projectors installed at the outdoor dance venue at the park I worked at.)

[Leo Enticknap]

We've suggested putting the projector in a pod in the past. The problem there is that the back wall is not weight bearing (the existing shelf structure is floor standing), meaning that architecturally, this would be a difficult and pricey undertaking.

Many thanks for the suggestions, especially a dual conversion UPS. I'll pass this along to the site contact. In the meantime, I'm hoping that his guy has been able to figure out the failure mode of the SMPS, and therefore fix that board to produce a good spare.