Lamp un-strikes (Strong Super 80)

[Ryan Gallagher]

Booth whack-a-mole. Solve one thing onto another.

Strong Super 80
Ushio UXL-40SC (4000w)
Strong R Series 4-7k rectifier.

Our No. 2 projector now will strike normally, and be on for a few minutes then either unstrike (and not restrike) or do quick hot strike, perhaps several, until eventually landing in an unstruck state. Often refusing to initiate again after an off/on cycle until some time has passed. While struck the ammeter and voltages are good.

This exhibited itself when we had swapped a lamp in No. 1 and were in the process of matching fields between the two. No. 2 was also slated for a new lamp so when returning to the task we did that first, cleaned all contacts pretty well, and the issue persists with the new lamp as well.

My instinct is it might be air-flow vane or PCB. Those particular spade connectors in pretty rusty looking. Might try to clean/replace those or temporarily force the vane switch down to rule that out.

It is worth noting that the supply is maybe a mismatch for the 4k lamps? Sticker claims 30-50v, but lamp wants 29v. But had never caused this issue prior, and doing it with two brands of lamps. (LTI was what we pulled).

But if the symptoms point to something else to try next please advise?

[Sam Chavez]

By memory, There are two vane switches, one on the blower in and also a vane switch within the stack. Both easily bypassed with a clip lead or what have you. You may need to clean the blower squirrel cage as they get pretty packed with dust.

[John Eickhof]

Do what Sam suggests also the door switches on strongs have a propensity to fail, make sure the door is secure, also make sure the exhaust is pulling enough air to counter act any sudden down drafts from winds, and that there is sufficient make-up air to the booth otherwise the exhaust is not going to work well. NOTE: the igniter PCB controls ignition only (to actuate the igniter to strike or light the bulb) if the bulb goes out the PCB has no control of that, it will be a lack of power from the rectifier either from a safety switch cut out, line voltage glitch, bulb,or bad bulb connection. Bulbs do not 'unstrike', thay just extinguish. Sounds like a switch problem...

[Ryan Gallagher]

By memory, There are two vane switches, one on the blower in and also a vane switch within the stack. Both easily bypassed with a clip lead or what have you. You may need to clean the blower squirrel cage as they get pretty packed with dust.

Thanks John and Sam, Will clip or bypass the blower vane switch and see if the behavior changes.

I don't "believe" there is one in the stack, there is no factory stack with these, just the grill and mating surface for your own exhaust ducting, but i'll definitely look again.
The one at the blower definitely actuates correctly when inspecting it with the door open and depressing the door switch, but rusty/corroded contacts may be at play. It meters for continuity as it should in both positions but that is without vibrations and heat in the house.

I'm leaning away from a door switch issue cause it would interrupt both fans and indicator light unless it's just an extremely momentary thing. Suppose I could bypass that in a separate test.

Squirrel Cage is relatively dust free (we have a very clean booth and no carpet etc).

[Mark Gulbrandsen]

Absolutely what Sam said! If a lamp dies AFTER striking, then poor air flow through the side intake blower or the stack blower. Kill the lamp house and look at the intake vanes on the blower wheel. That should answer your question on that. I suspect like your UPS batteries never having n\been changed, that the the blowers have never been cleaned. Also, what John said... I had a theater in WY that had bad down drafts on one screen after a new building went up next to his. The owner had the roof exhaust moved elsewhere on his building, and that fixed the issue...

[John Eickhof]

also, last but not least, if the booth is a recent installation and the main exhaust fan is a Granger/Dayton 6 or 8" squirrel cage, check the fan rotation! it may be turning backwards, the Dayton motors come from factory in wrong direction, thus the air flow will be poor! if it is, just reverse rotation in the motor terminal box also there was an airflow switch under the lamp deck that is accessible through an inspection cover that may be clogged with lint and dirt...look at the manual for its location..

[Dave Macaulay]

Can you tell if the rectifier actually shuts off? There would be a pretty good click from the contactor. You should be able to measure the DC voltage: it should be around 100VDC with lamp off, dropping to whatever like your 19VDC with lamp on. The HV pulse from the ignitor should be bypassed inside the lamphouse and not be a danger to your meter.
If it does shut off, something in the lamphouse safety circuit is causing it, as mentioned there are a bunch of door and airflow interlock switches and the AUTO/MANUAL switch involved in a series chain of them. The rectifier won't shut itself off except from an internal temperature interlock or an internal failure.
Also check the AC voltage from the rectifier to the lamphouse. The Super 80 wants 240V (IIRC) while ones like the Super Lumex run on 120. I don't know if 120 would work at all but if it does... the fans would be very slow and not trip the airflow switches.

[Mark Gulbrandsen]

Can you tell if the rectifier actually shuts off? There would be a pretty good click from the contactor.

No contactor in the strong Switchers. There is only a 240 to 120 step down transformer for feeding 120 V to power the lamp house. The actual on - off function is done by the internal control board shown below...

[Ryan Gallagher]

Managed the following during our music show last night:

Cleaned the squirrel cage fan blades, only enough dust to darken a q-tip per blade, and caught a couple smaller dust bunnies in the surround. Nothing significant. The vane is fully pegged against the switch when the blower is on, as it was before.

Metered at the switch posts for continuity when the vane is in both positions. Tests fine.

Bypassed the airflow switch (at the terminal posts of the switch), no change in lamp hot-strike/extinguish behavior. However I was only able to get a good meter continuity across the posts, when metering across the fairly crusty spade connectors on the posts it was more difficult, so there is a chance that connection is suspect, especially once heating/expansion comes into play. So effectively I bypassed the switch, but could still try bypassing those cables/connectors.

Also separately metered continuity when depressed vs not across all 4 door interlock posts. Those behave as expected, and never noticed any blower cutoff previously as would be expected if the door interlock was having issues. I still plan to bypass test that but didn't have time last night.

Next time I have a chance to test I will pay close attention to the indicators on the rectifier to see if there are any status blips on the LEDs and look into metering

Our roof exhaust stack is shared across 4 xenon lamp houses. Two SuperTrooper spots and 2 Super80 houses. Spots are never in use during film/testing and their vent is physically closed. I have not been to the roof to check out the outlet, but that is certainly worth doing also. When not in use we insert a board between the ducting and the super80 stack to avoid any moisture creeping in, and I've done some tests with the board still in place on the other projector, so double the airflow in the problem one. No change yet.

Will keep at the trouble shooting tasks next opportunity (Tuesday next).

TODO:
- Test by bypass connections (not just switch itself) at the vane switch.
- Test by bypass the door switch.
- Test by physically holding the vane switch closed
- Inspect roof outlet to exhaust.
- Begin to suspect Voltages/Rectifier and start down that sequence of troubleshooting steps.

Thanks all!

[John Eickhof]

what automation (if any) are you using? are these shutdowns happening when lamp is turned on manually? replace the lamp relay in the automation...switch lamps and see if problem follows the lamp...possible unstable lamp...check stabilization magnet in lamphouse and see if it is positioned correctly...

[Brad Miller]

Have you checked the Strong switcher's fans yet? If that gets a little bit too hot, the thermal inhibit will shut the lamp off until the supply cools down. To turn that off (for testing only), it's SW2 the second or "B" rocker switch on the control board. (ON=thermal protection is on / OFF=ignore any self-destruction that may be happening to the power supply)

Also you said you were getting 29 volts, but how many amps are you driving the bulb at?

Remember also that swapping out a switcher isn't that big of a task. I would be inclined to have you flip them between projectors so you can see if the problem stays with that lamphouse or moves with the switcher.

[Mark Gulbrandsen]

Can you tell if the rectifier actually shuts off?

Yes, it's easy to tell. Look at the LED indicators on the top of the unit as per the attached picture. All four green led's should be lit when it's running. If the "Go" LED goes out while the lamp is lit, then the lamp control loop (blower, blower micro switch, stack micro switch, or automation has issues. If any red LED's come on then you have a bad power supply. Note that Strong never did use teflon insulated wire in any of their lamp houses, and I have had shorts in the wiring cause some issues because of the insulation flaking off If you do have automation, then turn on the manual lamp switch on both the lamp house and automation lamp switch one at a time and see if the lamp lights again. If it does, then follow what John said. This whole thing can literally be figured out in 5 min... Out west there is so much crud floating in the air from Cottonwood Trees in some locations that lamp house blowers sometimes had to be cleaned 2X a year.

[Ryan Gallagher]

Thanks for the additional lines of inquiry...

Re: Automation... not using any. Fully manual booth, so have always operated houses in "manual" rather than "auto".

Re: Amps, if to be trusted the ammeter on that unit is showing in the range of 120-130A when the lamp is functioning. Though if you toggle to volts and back the needle doesn't always return to the same spot, indicator seems a little problematic.

Re: Supply. The rectifier vents get vaccumed periodically, but the fan blades probably have not been cleaned in eons. I did confirm that at least both blower fans in the rectifier were functioning. I will verify again next time i'm in the booth but my memory of the status lights is that there is NO CHANGE from the 4-green status while the problem is occurring.

Will add cleaning of rectifier fans to my list. And swapping the switcher does seem easier than swapping the whole supplies between projectors. Will consider that as well as the thermal protection bypass for testing.

Ohh and for John, The problem has already been present on two lamps. One new, one with only 211 hours on it (but installed for eons). Both before we did any cleaning/service and also after with the new lamp.

[Ryan Gallagher]

Here is an additional thought. Could it simply be a bad Cathode connection, that gets worse with thermal expansion?

The problem "First" occurred literally as I manipulated the lamp focus position. It then persisted occurring with that original lamp (would strike but then later start to restrike or extinguish). We chalked that timing up to coincidence at the time, assuming a good cleaning and lamp swap might solve it.

As we changed to the new lamp we wire-brushed out some rust from the Cathode collet and copper tongues, and cleaned it as best we could with tools at hand. Similar for the bolts on the anode and cathode leads with the addition of some CRC contact cleaner. But the problem remained.

If that is a possible cause, Is there any other product or method I should use to really improve the copper and clamp negative cathode connection? It's definitely clamped fully, but not trusting we got it clean enough? A similar cleaning method worked on our other projector, which had an even rustier cathode pin, but then it never had this issue either.

[Mark Gulbrandsen]

Thanks for the additional lines of inquiry...

"Re: Automation... not using any. Fully manual booth, so have always operated houses in "manual" rather than "auto"."

Ok...


"Re: Amps, if to be trusted the ammeter on that unit is showing in the range of 120-130A when the lamp is functioning. Though if you toggle to volts and back the needle doesn't always return to the same spot, indicator seems a little problematic."

It's a cheapo meter and a ten cent push button switch, they are all that way

"Re: Supply. The rectifier vents get vaccumed periodically, but the fan blades probably have not been cleaned in eons. I did confirm that at least both blower fans in the rectifier were functioning. I will verify again next time i'm in the booth but my memory of the status lights is that there is NO CHANGE from the 4-green status while the problem is occurring."

The last part is strange. if you can get it to happen again, look at the ammeter on the back of the lamphouse. The current would seriously drop, like to zero if the lamp extinguishes.

"Will add cleaning of rectifier fans to my list. And swapping the switcher does seem easier than swapping the whole supplies between projectors. Will consider that as well as the thermal protection bypass for testing."

The Switcher IS the whole supply...

Ohh and for John, The problem has already been present on two lamps. One new, one with only 211 hours on it (but installed for eons). Both before we did any cleaning/service and also after with the new lamp.

I never had this happen to an Ushio Lamp, either film or Digital.