Film-Tech Forum ARCHIVE: Advice for some Westar 2001 flickering niggles

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Posted by Gavin Lewarne (Member # 5397) on 08-29-2009, 03:27 PM:

Hi Everyone!

I am very new here, so i will introduce myself and my equipment!

Equipment:
2x Westrex 2001 (Century C? but mine were made in england)
Manual two machine changover system
Jaxlite red LED shoudhead retrofit (yeah i know its a jaxlite and they suck)
Dolby CP45
Cinemeccanica CX1600 lamphouses with OSRAM short Arcs
No automation
Reel to Reel operation
No automatic rewinder (everything done by hand)

Venue:
Independant one screen art house cinema
South West Endland

I was wondering if anybody could help me with some little niggling issues. Any thoughts or insight would be great!

1) Lamphouses are flickering quite noticeably. I changed the lamps, old ones were about 4 years old. I have made sure they are pulling 70a as rated on the box. I cannot tell you what the rectifiers are specifically, as there are no factory ID labels anywhere to be seen. They are about a foot and a half square, about 3 feet high with one giant knob that says " Adjust -->"

Any ideas on how to cure the flickering? it was doing it with the old lamps too so i know its most likely not the lamps. I have a set of new Diodes for each rectifier. I think it could be that? but i have no idea how to even take the rectifier apart without some serious dismantling required!

2) Would visible screen flicker be linked to the above? or could that be due to shutter timing? i have no motion blur or text ghosting so i dont think so myself but would like another opinion.

Thanks for your time!

Oh, and feel free to laugh at my ancient stuff, but to be honest, they are still (mostly) going strong. One is much more unreliable that the other one which is weird too!

Posted by Demetris Thoupis (Member # 833) on 08-29-2009, 03:37 PM:

Hi there. I suggest you check the faq and rules and change the topic name otherwise yu will be nagged. Some pictures of the rectifer will help us help you better.

Posted by Gavin Lewarne (Member # 5397) on 08-29-2009, 03:46 PM:

Thanks, just sorted it. I read the FAQ but was absent minded when i made up the title!

I can take some photos of the rectifiers tomorrow and upload them somewhere. would it be helpful if you had:
Frontal shot and open-cover shot? or something else?

Posted by Rick Raskin (Member # 1561) on 08-29-2009, 05:07 PM:

Welcome to film-tech.

Some additional information would be helpful:

One rectifier for the booth or one per machine?

Are they (it) connected to 3 Phase mains?

Do both machines exhibit the same problem?

My first guess would be a blown diode but that would be premature.

The folks here will probably nail the problem when they see your pictures and details.

Posted by Pete Naples (Member # 761) on 08-29-2009, 08:13 PM:

From the description, the rectifiers are probably T&R 123B/3, very common. T&R stand for Transformers & Rectifers, who are still in business but not making cinema rectifiers anymore.

What kind of fickering? A bad diode will manifest itself as a very regular up/down in the light with the machine running. Looks not unlike a lighthouse, it's actually a bear frequency between the flicker at 50Hz and the projector shutter at 48Hz.

If the flicker on screen makes the picture look like it's lit with firelight then it's more likely to be flame movement in the lamp, could be cooling or stability magnet issues. Also electrode damage from excessive ripple or inrush current.

If you're not sure what you're doing inside the rectifer, stay out of it! There is obviously mains voltage in there, also DC which will give you a very serious shock, and smoothing capacitors which can hold a charge for days. All waiting to catch the unwary....

Posted by Demetris Thoupis (Member # 833) on 08-30-2009, 07:52 AM:

Also years of bulbs don't mind just working hours so that you know. Considering the flickering as others proposed either a bad diode (or set) but it is advisable to change a whole set if one fails, a bad filter capacitor in the rectifier e.t.c. I don't think is your lamphouse as the CX1600 offers quite good ventilation and airflow in the lamphouse. Also make sure your lamp is adjusted correctly. Do you have any stiff projection angles? Sometimes even rotating the lamp cures the flickering.
Demetris

Posted by Gavin Lewarne (Member # 5397) on 08-30-2009, 11:40 AM:

Thanks for all the replies!

I hooked up my digital multimeter to the output of the rectifiers and monitored over a period of 2 hours. No significant fluctuations, and the lamps are not exhibiting the "light house" symptoms you describe.

Im fully competent to work in the rectifiers, just dont want to take them to bits for no reason, tis all!

Righto, so, probably not the Rectifiers then, so - ancient filter caps in the lighthouse?

i will take some pictures of the lamphouses with the cover off and the rectifiers asap and upload them!

For further info:

we have TWO rectifiers, one for each machine
Lamps are orientated vertical, no room to change that.

Posted by Pete Naples (Member # 761) on 08-30-2009, 12:32 PM:

The 'filter' or smoothing capacitors are in the rectifier, not the lamphouse.

Measuring the DC voltage at the output of the rectifer will tell you very little. You need to measure the AC ripple that is a component of the DC. There are various ways to do this. I use a true RMS clamp meter on one of the DC conductors, there are other methods involving a photocell and an oscilloscope. To measure DC inrush you need a clamp type meter capable of measuring DC inruch, a very rare and expensive beast.

Have a good look, clean and tighten up of all the connections in the DC circuit [Wink]

By "rotating the lamp" Demetris means rotating it 180 degrees on it's axis.

Posted by Demetris Thoupis (Member # 833) on 08-30-2009, 01:22 PM:

Thanks Peter for clarifying that

Posted by Gavin Lewarne (Member # 5397) on 08-30-2009, 01:28 PM:

can i have an opinion on something i have checked so far to see if i am going about this the right way?

The "flickering" is evident on brighter areas of the image, such as white walls and sky, but not on the darker areas. It is a high frequency flickering, at around 30hz or so frequency i would say. not majorly noticeable, but i can see it and i am a perfectionsit.

so in my search of the problem, i have tried:

1) 10 seconds of white screen, with no film in the machine at all. flicker still present. most likely not intermittent or film path / gate.

2) swapped power supplies going to the projectors. both machines still had symptoms.

3) swapped out lamps and tried my brand new spare, same problem both machines

4) fitted new PVC arc cables (old ones insulation had broken dows and cracked), cleand all lamphouse con nectors i could find

5) have now tried "rotating" the arcs. same problem

still, pics will be uploaded tomorrow or tuesday if i can [Smile]

Posted by Pete Naples (Member # 761) on 08-30-2009, 03:27 PM:

I wonder if you have too much light? How big is the screen? What wattage of lamp (I'm guessing 2kw from the 70A)

Try this.

Rotate the projector on the inching wheel until the shutter is in the open position.

Wedge the fire shutter assembly open (tie some string round the Watt governor bob-weights in the back to hold them out)

Fire up the lamp, and open the dowser to allow white light onto the screen, ONLY FOR A COUPLE OF SECONDS or you'll damage the lens. Don't be surprised if there's some burning of oily dust in the shutter housing. This will let you see what the light really looks like, without the 48Hz flicker from the projector.
By the way if your Westars are still on the doubly vee belt drive from the motor, the chances are they are running slow, as by now the pulleys will have worn. You can replace the belts and pulleys with timnig belts and sprockets to get round that.