Barco B series SM lamphouse - heat damage to adapter bolt

[Leo Enticknap]

On November 22 last year, I replaced the lamp (Ushio DXL-30BA/F) in a DP2K-19B, and in the process, found the bolt (M6x40mm or DIN 912) in the cathode adapter (R865555_02) completely seized in its thread. The little bastard just wasn't going anywhere with a regular T-handled Allen wrench. So I stuck a 5mm hex head on an 8" socket wrench, and immediately sheared the head off the bolt as I started to turn it. We had to replace the adapter, and even doing that was easier said then done, because it had seized into its holder in the back of the lamphouse. I had to disassemble the lamphouse to separate the lamp from the adapter, and then whack the adapter loose with a hammer.

I've just done the following bulb change on the same projector, and yet again, there is heat damage to the bolt.

buggered_bolt.jpg

As you can see, the worst of it is over about 10 thread revolutions in the middle. Thankfully, I managed to get this one out without destroying it in the process, and, obviously, have replaced it with new (I bought a bunch of them after the November 22 incident, and left them in the booth), this time with some lithium grease in the threads.

Both the last time this happened and just now, I checked the logs for fan RPMs and temperatures. All are in the normal range, with near identical figures to those of the other projectors, and there are no other signs of damage or any other weird symptoms with the incident projector. The lamphouse exhaust is also confirmed as working OK (at least to the feel - I haven't put an anemometer on it).

Any ideas as to what is going on?

[Marco Giustini]

Is it only the bolt showing heat damage? The lamp, the adaptor, the ground lead are all good? No other signs of heat damage anywhere else?

The Cathode area should be kept cool by that large fan which is getting air - if memory serves - from the card cage. Is the filter clean - and most importantly not clogged with grime? I know you probably know this but those metal mesh filters can clog to a point where a brush or a vacuum cleaner are not effective anymore. The quick test is that you should be able to shine a light through them once they're clean.

I do not remember whether that fan gets air from somewhere else as well.

About lithium grease, my concern is that it might reduce conductivity there? Maybe I am overthinking this but I just wanted to mention.

[Steve Guttag]

If you have not done so, I'd check the hex nut and the lamp adapter receiver. I'm finding those are loosening up over time. It is a 17Nm specification.

CathodeTorqueCapture.jpg

The "B" series part number is Z3499214K, Lamp House Cathode Adaptor + Nut + Wire (For DP-3000, DP90, DP100 and DPxK-B).

I've seen some of those get so hot that the nut just melts off. There is normally a label near the end of the cable...if its glue is oozing, you likely have problems.

[Mark Gulbrandsen]

Something is obviously NOT making good enough contact. It's either lose or was assembled in the wrong order with the associated lock washers. Placing the washer between the cable and head of the bolt may be presenting a slight resistance that could cause this over a number of months.

[Leo Enticknap]

Thanks for all the suggestions. Answers to questions:

• Confirmed, the only visible evidence of heat damage is on the bolt.
• The air filters are cleaned whenever a bulb is swapped out and at maintenance "C" time, and the steel mesh filters are also cleaned as part of maintenance C (usually with a stiff toothbrush and a Datavac). I know the air filters should be done every month, but the service contract does not include enough PM calls to do them monthly. All the other projectors have their air filters cleaned on the same schedule, and are not giving this trouble. Temperatures in the log are comparable to all the others.
• Lithium grease - thanks for the thought. Will use copper grease (conductive) on these bolts in future.
• Lamp adapter receiver - again, thanks for the thought. Have to confess that I didn't check it. Will do when next at the site.

I think Mark is on to something. I'm increasingly convinced that this is a DC conduction issue, not poor airflow causing overheating. I did notice that there wasn't a lock washer on that bolt, just a regular one (at least some of the other projectors have both on their bolt). Time to order some M6 lock washers, I guess.

I'll probably next be at the site on July 10, and will check all of these things out then. Thanks again for all the suggestions.

[Sam Chavez]

I recall Barco doing a field bulletin about original toothed lock washers not making good contact on series one applications.

[Jason Raftery]

If you have not done so, I'd check the hex nut and the lamp adapter receiver. I'm finding those are loosening up over time. It is a 17Nm specification.

CathodeTorqueCapture.jpg

The "B" series part number is Z3499214K, Lamp House Cathode Adaptor + Nut + Wire (For DP-3000, DP90, DP100 and DPxK-B).

I've seen some of those get so hot that the nut just melts off. There is normally a label near the end of the cable...if its glue is oozing, you likely have problems.

In addition to it loosening up, check the brass nut / lamp adapter receiver for cracks from someone over-tightening the cathode bolt. The kind of heat damage visible in the bolt is almost certainly from a high resistance connection rather than inadequate cooling. A bad enough connection can eventually do a number on the surrounding metal....

fried cathode connection.jpg
IMG_1056(1).jpg

[Steve Guttag]

Seriously Leo, I'd have both the cable/nut kit and the lamp adapter R865555K and just change them. They should almost be standard replacements on "D" Maintenance. Because that nut is hidden by the spring and "TO-3" plate, NOBODY ever checks it. It goes through thermal cycles and gets stressed on each lamp change. I'd be willing to wager the cost of the parts is trivial to a repeat service trip and/or going down.

Note, for "C" lamphouses, the one part includes everything, including the lamp adapter.

When you change all of those parts, you, once again, get a good fit and good electrical connection.

[Marco Giustini]

• The air filters are cleaned whenever a bulb is swapped out and at maintenance "C" time, and the steel mesh filters are also cleaned as part of maintenance C (usually with a stiff toothbrush and a Datavac). I know the air filters should be done every month, but the service contract does not include enough PM calls to do them monthly. All the other projectors have their air filters cleaned on the same schedule, and are not giving this trouble. Temperatures in the log are comparable to all the others.

What others said but also: sometimes toothbrush and vacuums are not enough with those filters - also I wouldn't recommend using either of those tools on them, they can be damaged pretty easily if the mesh is clogged by something else than dust.

Over time, with certain pollutants, the mesh just gets clogged and needs water and soap to clean, there is an info-T about that. Worst case it might need some caustic solution to dissolve grease. With London's air, hot water and soap is enough.

Once the filter is cleaned, you should be able to see through them. If you can't, the filter is not cleaned.

Took me a while but I found the pictures I had in mind. That's the same Barco filter, vacuumed, and then washed.


20170404_091530.jpg
20170404_100521.jpg

The above doesn't mean to patronise you in any way, Leo. I'm just sharing my experience hoping to be helpful You probably know all of this already.

[Dave Macaulay]

I've seen this many times. It has always been due to the Allen screw being lose. In multiscreen sites I often find other projectors with them loose but not yet blackened. I have a torque driver, and the spec torque is not super tight but pretty snug.
it should not have a lock washer. If it does heat up, the temper is lost in that washer and your problem gets much worse.
I haven't found any that I suspected the DC cable connection was bad but that could happen.
The problem is complex... poor training of whoever changes lamps, staff turnover with poor or no training of new staff, lack of proper tools.
I see the screws loose, the cathode adapters loose, the anode adapter cable connection loose, and the anode connector slipped into the inner case slot. That last one ends up needing a new cable (comes with the cathode block etc), new connector and insulator, and often a new SPG. Expensive mistake.

[Leo Enticknap]

What others said but also: sometimes toothbrush and vacuums are not enough with those filters

I meant the steel mesh filters on the card cage bulkhead and the large fan under the light engine compartment, not the qauze air filters. The gauze filters are washed and dried.

I always tighten the bolts properly. None of this heat damage is evident on the nuts of any other Barco I have changed a lamp in and returned to a few months later to do the next one, so I don't think this is the problem, either.

it should not have a lock washer. If it does heat up, the temper is lost in that washer and your problem gets much worse.

I don't know for sure, but suspect that they come from the factory with a lock washer, and a regular flat washer. Certainly most of those adapter bolts I've handled have had one, and on the few that didn't, I'd always assumed that it had got lost and no-one ever bothered to replace it. I'd be surprised if someone before me had made the proactive decision to add the lock washer.

Will check out the nut of the cable/nut kit the next time I'm there - thanks.

[Marco Giustini]

I meant the steel mesh filters on the card cage bulkhead and the large fan under the light engine compartment, not the qauze air filters. The gauze filters are washed and dried.

I cannot remember where the centrifugal fan blowing on the cathode is getting air from. I kind of remember it was from the card cage, hence my suggestion about the main filter. But if all is good, then that's not the issue.

[Dave Macaulay]

I cannot remember where the centrifugal fan blowing on the cathode is getting air from.
On C series, it gets air from the bottom of the chassis... a bunch of slots cut into the chassis metal. These do get plugged up with oil/dust gunk if popcorn smoke is in the booth (ie if you can smell the popcorn cooking there) and even catch a lot of just dust if there's no smoke. It's part of the maintenance to clean them for us. I install C units with the projector legs up enough to be able to reach under there. I doubt if airflow could normally be restricted enough to cause the adapter to overheat enough to blacken the Allen screw.
For B, I don't remember either. But I don't think it gets air through the front filter, might though of course. That is a big filter compared to a C for the same boards.

For the metal filters, popcorn smoke is a huge contributor to fouling them. Barco says use hot water with washing soda and soak them for a long time. Many issues with that: maybe washing soda (sodium carbonate) is common in Belgium but not here. A pan big enough to soak a main filter on a C let alone a B is not common in cinemas. Washing soda does not dissolve easily (even in hot water). I rarely have an hour to soak filters. I did find washing soda both at a hardware store and a pool supply place (used as pH+) but due to the last three problems I now use either a commercial grill/oven cleaner (Swish 5100) which is a strong lye solution or normal grocery store spray oven cleaner and let it sit for a while then brush it clean (toothbrush works) against a flat surface to avoid popping the mesh out, followed by a thorough rinsing. The filters come out like new. Just a soak in water with dish detergent and brushing is enough for dry dust buildup. Same treatment for the E and S series "paper" washable filters.
Note that the 5100 spraying produces a weapons grade corrosive gas cloud that you won't like breathing, but a covid type face mask helps a lot. Consumer oven cleaner spray is nasty too but it isn't nearly as bad as the 5100. Or as effective as fast.
I have found ridiculously clogged mesh filters, looking like a 70s shag carpet. The only symptom other than the extreme fan speed drop when they are removed is higher than normal temperature readings on board components like the ICP FPGA. I haven't seen any temp alarms triggers or performance issues but component life is always shorter at higher temps.

[Leo Enticknap]

Couldn't agree more. Washing soda is not something that is readily available here, and on a typical PM call, we don't have time to soak them in a large bucket of it, wait 2-3 hours, rinse them, wait for them to dry, and then reinstall. If a site I'm servicing has a sink available, I will wash them in a solution with a little dish soap (UK: washing up liquid) as the first step in a PM, stand them to dry while I do the rest of the tasks, and then reinstall at the end. If the site cannot make a sink available (and I service a few museum and high end residence type places that won't allow me to clean filters in the restroom), then I'll hold a Datavac close to the side without the crap on it, and blow away through the filter gauze as much of it as I can. Thankfully, these sites, by their nature, are ones that don't have any popcorn oil in the atmosphere, the dust on the filter is dry, and so that usually does the trick.

I will next get a chance to look at the frying bolt projector on July 6, will check out the DC lead and nut then, and report back. Thanks everyone.

[Steve Guttag]

For some PM calls, I'd bring a split bucket.

https://www.homedepot.com/p/Rubberma...E&gclsrc=aw.ds

Fill one half with hot water and Arm and Hammer's "Super Washing Soda"

https://www.amazon.com/Arm-Hammer-Su...8124174&sr=8-2

About a palmful to a gallon of HOT water. The other side, just cold water. With that solution, normally, the wash is on the order of 1 minute and the popcorn soot just rolls off. A quick dunk in the clean water and blot dry. They are metal. They are not going to absorb water like a paper/fiber filter will. They should dry pretty quickly with a paper towel or rag. One should blot them, not rub (which can damage the screens.