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I don't like using capacitor checkers. They don't tell the full story.

Looking back on electronic theory I seem to remember that if a capacitor checker is used to check capacitance and the results are higher than expected, the capacitor is electrically leaking.

Can someone refresh my memory on that?

Several people at Amprobe and Irem's US reps told me that using an AC clamp on amp meter would not be too accurate. Several people would try to use their AC clamp-on meter, since ripple is a form a of AC.

People might take issue with my suggesting to disconnect the AC ground to the 'scope. Battery-operated 'scopes were mostly dream when I wrote this. So, use at your own risk, and let common sense prevail, but I still do it this way today.

Determining the percentage of ripple in
power supplies for short-arc xenon lamphouses.

This procedure also checks for any error in the voltage and/
or ammeter.

Before beginning, verify that the power supply is operating at
or below the AMPERAGE shown on the power supply nameplate.

1. With a small flat head screwdriver, "zero" the volt meter and
ammeter (if installed).

2. Set the oscilloscope to 10 millivolts per division; the time
base to 20 milliseconds per division.
Avoid using "X10" probes.
There are no special triggering requirements, AC or "AUTO"
will work.

Note: Since the oscilloscope will be reading DC, greater
accuracy can be obtained by adjusting the scope's
baseline to the bottom of the screen, rather then to
the center.

3. Place the auto-ignition switch to "MANUAL".

4. Open the lamphouse door and defeat the door interlock safety
switch.

5. Observing proper polarity, connect a calibrated volt meter to
the DC power cables.

6. Power on the lamphouse. The bulb should not ignite while the
auto-ignition switch is in "MANUAL".

7. Compare the voltage reading from each volt meter. Record the
values. Replace the meter in the lamphouse if the values are
more then 15% apart.

8. Remove the power to the lamphouse while the meter is still
connected.

9. While observing the voltage decrease, listen for the RA
relay (inside the rectifier) to drop out. Record this value.
It should be between 30 to 45 volts.

Note: It should take longer then 10 seconds for the meter to
reach zero.

10. Remove the volt meter when the value reaches zero.

11. Power on the lamphouse.
a. Press the "STRIKE" button to ignite the lamp OR:
b. If there is no "STRIKE" button:
Flip the auto-ignition switch to "AUTO", then
immediately return it to "MANUAL" after the bulb is
lit.

The auto-igniter must be disabled. If the bulb should go
out, it can not re-ignite and injure someone
connecting leads or damage test equipment.

12. Connect the oscilloscope across the ammeter shunt.
Record Imax (total peak voltage)
Record Imin (minimum peak voltage)
Calculate ripple and record. The percentage of ripple should
be less then 10%.

Note that the oscilloscope may have to be isolated by plugging
a ground adapter in series with the oscilloscope's power line.
Use caution.

13. Record the lamphouse ammeter value.
Because the ammeter shunt reduces the actual current
value to the lamphouse ammeter by 1/3000, there
will be 3 amps for every 1 millivolt shown on the
oscilloscope. Therefore, the amperage can be calculated
by multiplying Imax, in millivolts, times 3000.
For example:

36 mv * 3000 = 108 amps

Note that this test requires an accurate 150 mv shunt.

14. Compare the readings from the ammeter and the calculated
current. Record the values. Replace the meter in the
lamphouse if the values are more then 15% apart.

15. Return the door safety interlock switch to normal.

Just pitch the IREM altogether and install your favorite other brand and watch the lamp life increase and realize, it was probably the ripple in the beautiful to look at but horrible power IREM rectifier.

Christie rectifiers powering Christie lamps...has got to be the toughest act to beat. To consistantly obtain 2-3 times rated life out of lamps, regardless of size speaks to their construction.

Steve

JOhn, Osram use to have a standard .1% accuracy shunt they would send out for investigating lamp failures. Your procedure is very correct except I used a storage scope instead and also measured and calculated inrush current at the same time, using the same shunt. I ahev an ORC ripple and inrush meter that I ahve had for years. Is till use it fairly often and ahve compared it to the standard shunt on one occasion. The amprobe they use is an AC/DC version and it feeds a special circuit in a black box. The calibration of the ORC unit was pretty close to the standard shunt so I always just stuck with the ORC system.

Mark

So basically, what you are saying is to use glass filled diodes and everything will be fine on the diode failure front? Hmm. Seems like a cheap solution to me.

The current Christie standalones all have fans on them and Christie was putting fans on their console units about halfway into the K series.

As to switchers vs Christie...even Cineplex pulled the switchers out for the Christies at the Uptown after the 6th failure...the result, no rectifier failures in years and much improved lamp life.

Mark, you know that newer isn't necessarily better...it isn't an excuse to use something...what switchers bring to the table is size and weight. I do use them for smaller lamps...look at my picture in the picture test thread..there is a Strong switcher sitting nicely between the Kinoton's feet, like it was sized to go there!

Steve

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"Old projectionists never die, they just changeover!"

As far as diodes go always get replacements thata re glass filled. Its easy to spot an IR cheapo epoxy filled version. Dull looking blue or green colored fill. Glass filled/sealed diodes have a very shiny appearance to them. My experisnce is that if you use glass filled you almost never ever go back, unless lightening hits.
Mark

In our entire chain, we've changed very few diodes. But for some reason, I've had to change 6 within the last two months; At two separate theaters the same thing happened; two went in the same power supply, then one in the house next to it. Each one went a few weeks apart from another. Very strange. At our Miami FL location, the power is always going out, brownouts, etc. but no diodes have blown. In our Trumbull CT location where the power is well regulated, three have gone bad in the last 2 months. So, go figure.

Perhaps your customers don't see it but I have repeatedly. As to IREM, they consistently rack up the shortest hours with the most ripple.

Steve

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Now the Christies.... those seem to be pretty good too, the 12 that are local to me are knocking on in years a bit now, but have been fretty reliable. All recently had new smoothing caps fitted as the ripple was getting a tad high. I had one real spectacular failure on one Christie. Two diodes failesd short, and in turn took out most of the snubber network in smoke and flames fashion. I had to completely remove that rectifier from the console to work on it and rapidly discovered that the Christie is surprisingly heavy for it's size!