Not too happy with Ushio BTN 750W/120V bulbs - alternatives?

[JLNorthGA]

When we installed all of our Altman 65Q Fresnel instruments this past winter, we used Ushio bulbs. I'm not having really good luck with them. They seem to be a bit "fragile". I am not bouncing the instrument around or anything, I'm just adjusting the angles. I've had to replace two bulbs. I probably have less than 100 hours on the bulbs. Are there "more sturdy" BTN bulbs?

[BLPisani]

IIRC, I've frequently used Broadway lamps. Osram Sylvania lamps are good in my opinion, though they may cost a bit more. I'd check with some of your more local distributors to see what brands they carry and sell most frequently.

[JD]

They do sound a bit troublesome, but a good rule of thumb is that while aiming, do not run the lamps to 100%
I always used 75% while aiming, bright enough to see but not near the point where the filament softens out.

[JLNorthGA]

They do sound a bit troublesome, but a good rule of thumb is that while aiming, do not run the lamps to 100%
I always used 75% while aiming, bright enough to see but not near the point where the filament softens out.

In point of fact, I never run the lamps over 70%. I typically run them at 60% (30-40% while aiming). Maybe I should just get some lower wattage bulbs and run them a bit hotter.

[derekleffew]

... Maybe I should just get some lower wattage bulbs and run them a bit hotter.

That certainly won't help your filament shock issues. If you're happy with the intensity, life, and color temperature, stay with what you have. If you want to more closely match your Source Four units, consider the 575W BTH lamp: New Fresnel Lamp . (I wonder if a 750W, HPL-"style" is in the pipeline?)

In comparing pictures of the Ushio and GE BTNs,

(Ushio on left, GE on right) BulbConnection.com - $15.23 Ushio 1000085 BTN Replacement Lamp
neither lamp appears to have any more or less filament support than the other. But pictures can be deceiving or incorrect; you might want to order another brand just to compare.

Most of us have experienced a failure during Fresnel focus when jarring a lamp due to a stuck sled (thus the primary advantage of screw focus Fresnels--the ones with a crank) or a too tight bolt that suddenly without warning becomes free. One way to avoid this is to unplug the unit before doing any major adjustments, but the hot plugging to turn the fixture back on may be worse than the jostling itself. The best answer may be just to take more care and be more gentle. Whisper sweet nothings in its ear.

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Something mentioned on another forum: the lamp manufacturers seem to be making the center contact on the MPF lamps smaller than they used to, or the springs in the sockets are weaker than they used to be, but many have reported more arcing with newer fixtures than they used to have. Can anyone attest to this? I can't recall a time in the past ten years when I've actually used a 6"FS.

[JLNorthGA]

The best answer may be just to take more care and be more gentle. Whisper sweet nothings in its ear.

Sweet nothings - chocolate covered null sets?

I'll try to be more gentle. I realized that the new Fresnel instruments sort of "stick" after they've been on for the run of a show. Possibly some high temperature teflon lubricant or something might be in order.

[joeb]

Something mentioned on another forum: the lamp manufacturers seem to be making the center contact on the MPF lamps smaller than they used to, or the springs in the sockets are weaker than they used to be, but many have reported more arcing with newer fixtures than they used to have. Can anyone attest to this? I can't recall a time in the past ten years when I've actually used a 6"FS.

I would say that it seems the springs on the newer Altman fresnels are a lot weaker than those on the older units. I have had to replace more sockets on the 6" fresnels we received with a new venue (less than 5 years old) than I have had to on similar units that have been in regular use since the 80's. With the exception of the socket, nearly all parts of the instruments (the new ones and the ones that are 20-30 years old) seem identical and interchangeable. One thing that seems to possibly contribute to this is the shape of the center contact in the socket. In the older units, it is completely flat where it comes in contact with the center of the lamp. The newer sockets are concave/cup shaped in the center. Perhaps this is to fit more tightly with the rounded contact on the lamp, but it seems to make much less contact than the old style. This ends up being where much of the arcing occurs. I don't know if it's this arcing that leads to the springs getting stuck, or if the spring itself is the issue. Either way, it is certainly a very frustrating issue.*

[derekleffew]

Not Fresnel lamps, but it illustrates the (possible) issue:

[zmb]

I'll try to be more gentle. I realized that the new Fresnel instruments sort of "stick" after they've been on for the run of a show. Possibly some high temperature teflon lubricant or something might be in order.

I've had that experience too with Altman 165Qs that aren't anywhere near new. I don't think adding a lubricant would be a fix because my personal thought is that everything expands when really well heated. But how and why would you be trying to make adjustments after the run of a show? Welding gloves?

[JLNorthGA]

I've had that experience too with Altman 165Qs that aren't anywhere near new. I don't think adding a lubricant would be a fix because my personal thought is that everything expands when really well heated. But how and why would you be trying to make adjustments after the run of a show? Welding gloves?

I mispoke. After a show is ended, the fresnels sit for several weeks. Then they have to be reaimed for the next show. They stick. It is difficult to adjust the angle - you really have to be quite firm. You can loosen the knob, but you still can't easily change the angle.

[JD]

Not Fresnel lamps, but it illustrates the (possible) issue:

What they are doing on the new lamps is "getting the lead out." The old style was soldered on. The new style has a crimp tube inside and the feed wire is crimped. The contact should actually make better contact then the old solder contact, which had a higher resistance. Of course, "should" and "do" are two different words.

[joeb]

The issue I've noticed is on the spring loaded contact in the socket, not the lamp base. It is flat in older sockets and concave in the newer sockets.