Film-Tech Forum ARCHIVE: Orc 1000 problem

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Posted by Bill Duelly (Member # 3612) on 07-05-2012, 05:33 AM:

I cant seem to get my lamphouse to strike. Here the symptons.... I turn it on and the spark gap sizzles/sparks. I had a brief flash from the bulb but nothing after that. I seemed to recall that power may be an issue with these and the voltage coming into the house was around 106/107 last night. This am, when it was up around 117, i tried again, no change. I have double checked the gap, which is one dime wide. The bulb has not shown any signs of problems and is clear. Any thoughts anyone? Many thanks

Posted by Pete Lawrence (Member # 130) on 07-05-2012, 07:58 AM:

I don't claim to be an expert on these, but I have two of them I've been able to keep running for a number of years. If you can measure some voltages, here's what to look for. First remove the top cover. Mounted on the bulkhead in the middle you will find a plug-in relay. Remove that relay to keep the igniter from firing and frying both you and your meter. Look for a single blocking diode (stud mount package) attached to the bulkhead. The lamp side of the diode should have one or more ceramic bypass caps between the lead and ground. Main lamp current goes through this diode. I found this diode had failed on both of my M1000 lamps. Now some measurements. There is an interlock switch near the top of the bulkhead. You'll have to press that to get the lamp supplies to power up. Measure the DC voltage to ground on both sides of the diode mentioned above. The lamp side (boost supply) should read around +100 Volts DC. The power supply side (main supply) should read +40 Volts or so. Since the lamp is not lit at this time the main supply is not regulating and at its maximum voltage. The key here is the lamp side of the diode must be at a higher voltage than the main power supply side. If these voltages are present at about these levels the diode diode may have failed open. To test this, turn the power off, discharge everything to ground (!!!), and measure across the diode with an ohm meter. Readings should be different when you reverse the meter leads. If this blocking diode checks good and you don't get about 35 - 40 volts on the main supply side you have a main supply/regulator problem. Hope this makes sense.

Posted by Bill Duelly (Member # 3612) on 07-05-2012, 06:43 PM:

Pete, thanks for the info. One side is 40 v but the other reads about 225v

Posted by Pete Lawrence (Member # 130) on 07-05-2012, 08:11 PM:

The two voltage readings sound fine. Normally the higher of the two wouldn't get much above 130 Volts and only for a short time. At that voltage the relay would close, fire the igniter, and light the bulb. Once the bulb conducts the DC voltage across it is about 27 to 30 volts or so. So it looks like the blocking diode may be open. You can check that with an ohm meter as I described above. Make sure both sides of the diode are discharged to ground first. Do the low voltage side first then the high voltage side, then repeat. If you short the high voltage side first you could pull a big current spike through the diode (if it's still good) and damage it. I usually use some low value resistor (25 Ohms or so), NOT a screw driver, to discharge power supplies. After your sure everything is discharged you can make your resistance measurement. You may have to disconnect one side of the diode to get an accurate meter reading. Just take off the mounting nut and separate the wires from the diode. It's not necessary to unsolder anything. Remember where all the washers were when it comes time to re-connect it. I'll bet the diode is open, but it's still possible the main supply has a problem.

Posted by Bill Duelly (Member # 3612) on 07-06-2012, 08:50 AM:

Havent had a chance to test that diode for resistance yet, but i ordered a replacement before the weekend started. Just as an fyi, the one there is designated IN 2131A. And i've been told that te replacement for that now is: NTE 6026

Posted by Bill Duelly (Member # 3612) on 07-06-2012, 03:22 PM:

Ok, disconnected the diode from the wires Open in one direction 135k ohms in the other.

Posted by Tony Bandiera Jr (Member # 2365) on 07-06-2012, 11:19 PM:

Yep that's a classic open diode. Be sure to use heat sink compound when replacing it and don't overtorque the stud/nut.

Posted by Bill Duelly (Member # 3612) on 07-07-2012, 12:11 PM:

Am i mistaken that isnt that what diodes are supposed to do? Block current in one direction (open) and a lower resistance (135k in this case) to allow flow in the other?

Posted by Pete Lawrence (Member # 130) on 07-07-2012, 12:21 PM:

It seems this problem is contagious. Now my M1000 won't light either. The same blocking diode we have been discussing has literally fallen apart in mine. I opened the top cover to take a couple of measurements just to see if the wires had to be disconnected for a clean good/bad reading. The solder-on anode lead could be easily moved. Well that's wrong! Turns out the seal between the anode and the case has shattered. So it's time for a new blocking diode. I ordered a couple diodes with somewhat higher specs as a replacement. It's been suggested in other discussions of this lamp house that the ratings of the OEM part are marginal, and I agree. I don't like NTE replacement parts as they simply take someone else's product and put it in their plastic bag. And they double or triple the price of the part.

Bill, you mentioned something in your first post that I didn't catch at the time. "I turn it on and the spark gap sizzles/sparks. I had a brief flash from the bulb but nothing after that." What should happen is about 3 to 5 seconds after you throw the main switch the igniter should fire with a quick snap and the lamp should flash on very briefly as the boost supply dumps it's charge through the lamp. This ignition attempt (flash) should repeat every 3 to 5 seconds if the lamp fails to light normally. There should be no "sizzles".

In reply to your last post, the 135K Ohm reading in the forward direction seems high. But it's very dependent on the type of meter. Many newer digital meters have an actual diode test position where you can read the forward voltage drop of the diode. A much better test. But even that isn't conclusive as your meter is using about 1 mA to test a diode that normally passes many amps.

Posted by Bill Duelly (Member # 3612) on 07-07-2012, 03:50 PM:

Does someone know what the correct distance is for the spark gap on this? I know I had kept the paper that came with this replacement piece, but alas waters from Irene washed it away. [Mad]

Posted by Bill Duelly (Member # 3612) on 07-07-2012, 06:24 PM:

Am i mistaken that isnt that what diodes are supposed to do? Block current in one direction (open) and a lower resistance (135k in this case) to allow flow in the other?

Posted by Tony Bandiera Jr (Member # 2365) on 07-07-2012, 09:02 PM:

No Bill you are not mistaken. The 135k ohms is way too high, it should be low (around 30-40 ohms IIRC) in the "forward bias" direction.

Posted by Pete Lawrence (Member # 130) on 07-08-2012, 02:10 PM:

I can't help you with the spark gap distance as the ones in my lamps are in a little sealed glass tube. The glass is clouded over and I cant see the actual gap.

With regard to measuring diodes with an ohmmeter...
When you try to use an instrument designed to measure parts that obey Ohm's law (like resistors) on components that don't obey Ohm's law (diodes and other semiconductors) you get inaccurate and/or false readings. The only way to accurately test semiconductors is with a curve tracer that can apply full rated voltage and current to the device under test. There are other simple tests that can be done, like run 40 amps through the diode and measure the forward voltage drop for instance. But that doesn't give a complete picture. A simple ohmmeter can check for some failures, like dead shorts or opens with some confidence. But in other cases your meter will lie to you. For example, the 135K Ohm measurement you got in the forward direction would imply (using Ohm's law, E=I*R) that it would require 5,400,000 volts to get 40 Amps to flow through that diode. We know that's wrong. Even Tony's 30 Ohms would require 1,200 Volts for 40 Amps to flow. That value is also wrong. Basically what I'm saying is you can't trust your ohmmeter to give correct readings in all cases. The bad diode I have checked fine using my digital meter. It even checked good when I set up a 15 Volt DC power supply and a light bulb to see if it would pass current in the forward direction and block in the reverse direction. My error here is the light bulb only drew around 20 mA not 40 Amps. When I cut open the diode case I found the silicon diode chip pretty much splattered around the inside of the package. But under low current and voltage it would still act like a diode. Hope this explanation helps some.

Posted by Louis Bornwasser (Member # 3063) on 07-08-2012, 02:53 PM:

Old timers in the Altec Service days used a switch leg to a 100 watt light bulb. Nothing and full brightness are wrong; dim bulb is correct. Louis

Posted by Ian Parfrey (Member # 5122) on 07-09-2012, 01:00 PM:

I had one of these units before with a similar problem. This was rectified by removing the glass spark gap, throwing it away and installing a Kinoton adjustable spark gap. Bingo! Problem fixed.

It may also be worthwhile doing a re-cap of the supply. These lamphouses are getting on in years and the supply gets baked fairly easily.

Posted by Sean Weitzel (Member # 244) on 07-09-2012, 02:26 PM:

The spark gap in my 1000 was bad as well, the leads shorted through the epoxy base creating a carbon bridge.

This spark gap is NLA so the Kinoton unit is really the only replacement.

Posted by Bill Duelly (Member # 3612) on 07-10-2012, 11:25 AM:

I called Strong - Ballantyne. Evidently Dale is no longer there but John Luhrs was very helpful. Some items of note:

The replacement spark gap unit should be at about 1/16" for the 750 or 1K bulbs (.0625" for the width testers) Making a wider gap will cause a more powerful surge in the ignition as it has to get to a higher voltage before it will jump (when testing this AM, my gap was a hair wider and when I turned it on, it made some very powerful sounding attempts).

He also noted that the 106 volts were totally NG. He suggested getting a "buck/boost' transformer to bring the voltage up.

So now that the heat spell broke and power to house was back at 117v, and the gap width reset, the lamp did light this AM. I'll continue to monitor it over the next few days and I will replace the diode when it comes in, after all, it would be significantly newer than whats already there. I'll also look to see what can be done power wise.

Posted by Robert Throop (Member # 61) on 07-10-2012, 07:03 PM:

I once used a spark gap from an Irem igniter in an ORC 1600 lamphouse. If memory serves I used a standard fuse holder to plug the sg into.

Posted by Pete Lawrence (Member # 130) on 07-11-2012, 11:10 AM:

Well, so much for diagnosing problems over the internet. Your blocking diode is probably OK. At least for now. [evil]

Your 106 Volts is indeed low. While there is no "law" as such, the accepted standard is (copied from Wikipedia):

"In the United States[3] and Canada,[4] national standards specify that the nominal voltage at the source should be 120 V and allow a range of 114 to 126 V (RMS) (−5% to +5%)." (Ref 3 is ANSI C84.1, Ref 4 is CSA C3-235) And like most things, it's really somewhat more complicated than that one sentence.

Line voltage at my house is typically 120 to 130 Volts. And that's with a voltage regulating transformer in the circuit about a mile down the road. There has been a long running feud here between the power company and a big wood working company (that makes kitchen cabinets) as to who is going to pay for the service upgrade. We residential customers are just along for the ride as our power feeds off the same supply lines.

If your handy making things, you should be able to build a usable adjustable spark gap from a piece of plastic and two 4-40 screws. Just grind or file the ends of the screws to a point. Add a couple nuts to lock the gap width in place. Try to keep the overall lead length about the same as the original. Your igniter is really a spark gap RF transmitter, and lead inductance (lengths) can affect its operation.

Posted by Bill Duelly (Member # 3612) on 07-16-2012, 07:10 AM:

To continue with updates:

It appears that spark gap is proper now and all is screwed down tight on the ignitor board (the connections might not have been real tight before around the spark gap.

Striking wise it seems immaterial whether it is 107-114 (which is within the range that the manual says will work) with the following exceptions: a 750 W bulb will light within 30 seconds and a 1000w bulb will be 1-2 minutes to strike. Which is better than before when the darn thing wouldn't strike.

In a condition such as mentioned above, the manual states that the capacitors should be 'reformed'. I have not done this yet, but I suspect age is an issue with them. Would the ones that are being 'reformed' be those big blue power ones visible when first opened and the smaller ones just under the reflector by the center bulkhead?

As always, many thanks to all for their input!

Posted by Pete Lawrence (Member # 130) on 07-17-2012, 08:03 PM:

Bill,
It would be helpful if you would describe what you see and hear happening between when you flip the main switch and when the lamp lights. What's going on in that 30 seconds to two minutes is very telling.

As to "reforming" the capacitors...
The M1000 book says pull the ignitor relay, turn the main switch on and wait for 5 minutes or so. What that does is apply full voltage to both the main supply filter caps (the blue cans behind the center bulkhead) and the boost supply caps (the ones in front of the bulkhead below the reflector). That presumes both sets of capacitors are in reasonably good condition and not to leaky. If you have a lamp house with capacitors from the 1970's, I would be a little more gentle with them. Applying full voltage, with no current limiting, to a big capacitor with high leakage current (from sitting for years) can make a loud noise and a big mess when it explodes.

A safer way is to apply a controlled voltage (from an external power supply) to the capacitor you want to reform through a current limiting resistor. Any value around 10K will work. Disconnect one side of the cap you want to reform from whatever it's connected to. Connect the external supply through the limiting resistor to the capacitor. Make sure the polarity is right! Start with the external supply at a low voltage and measure the voltage across this 10K limiting resistor. There will be some voltage across the resistor as current flows while the capacitor charges up, but it should go to near zero after a few seconds to a minute. Once the voltage across the resistor drops near zero you can raise the supply voltage a little more. There should be a voltage across the resistor again, until the capacitor finishes charging up to the new voltage. Continue this process until the applied voltage reaches the capacitors working voltage limit. Then just let it sit for a while with full voltage applied. What you have done is reform the oxide dielectric in the capacitor slowly and limited the charging current in the process. Make sure you discharge the capacitor before you reconnect it to the circuit.

Having said all that, if you have been using the lamp house until recently the capacitors are probably in fairly good shape. The book method of reforming is what happens when the lamp doesn't light. Full voltage is applied to both sets of capacitors until the lamp lights.

Google "reforming electrolytic capacitors" for more info. The tube guys have been doing this for many years.

Posted by Pete Lawrence (Member # 130) on 07-18-2012, 06:26 AM:

Added to the above (because edit time limit has expired):
If the capacitors survived the reforming process it means the leakage current is under control. It doesn't mean they are at full rated capacitance. If they have dried out over the years the capacitance value is likely to be much lower than what it should be.

Posted by Bill Duelly (Member # 3612) on 07-20-2012, 04:08 PM:

So heres whats been happening , or not happening:

I have replaced the upper blocking diode and the 2 big capaciters up top. I then put the 1k bulb inthat i had been using that, that had NOT been able to work recently (I was using a 750 bulb with mixed results for the past few days) I reformed the caps and the bulb came in like 2 seconds. A few minutes later it was 4 seconds or so. This am it was about 15 seconds a few hours later about 1.5 minutes and just recently it was 3 minutes. At all times the voltage was about 117-119.

So what is happening is that the start time keeps getting longer. So is something leaking or draining? There is no other noise happening until the bulb strikes and there is the brief zap.

Any hints would be appreciated.

Posted by Tony Bandiera Jr (Member # 2365) on 07-20-2012, 04:30 PM:

Yeah it is time to dumpster that piece of crap and get a real lamphouse and rectifer. [Smile]

Jim Henk has a clean 1k setup for sale in the Equipment forum that will give you more light and work a lot better.

If you really are in love with that thing, then replace ALL of the caps including the ones on the control and scr boards. With the tight packing of the electronics, the heat it generates and the age of it, you have a high probability that a lot of the caps are dried out and nowhere near spec.

Posted by Bill Duelly (Member # 3612) on 07-23-2012, 07:43 AM:

Yes Tony, i do love that unit. It reminds me of one of the houses I worked at from the 80's into the 90's, where I do have the sound head and ped from.

For laughs i did swap out the boards with another unit that was working so so. That certainly effected the operation of the unit, making it better but by no means perfect. Those were old boards as well. So off to the electronics store to buy some capacitors! Warm up that soldering iron....

Posted by Richard Fowler (Member # 893) on 07-23-2012, 12:28 PM:

I had a customer who had them for dailies rental in which we gutted the power supply from the lamphouse and placed them in a separate box...

Posted by Bill Duelly (Member # 3612) on 07-26-2012, 09:27 AM:

Just to keep updated... I replaced a bunch of caps but still intermittant issues, even trying different boards and bulbs. Went through ALL the test points and everything was metering ok. Which left one thing...spark gap. Moved it closer than strongs' 1/16th recommendation and viola! It worked. Then went back to double check bulbs and found that I had to readjust the gap a different way for each of the 3 bulbs )1 x 750 and 2x1000), all used to various degrees. So the secret could be that the 'replacement gap', with the 2 adjustable screw posts, needs to be tweeked first for what ever bulb is put in.

Posted by Pete Naples (Member # 761) on 07-26-2012, 12:59 PM:

Richard, did something similar a number of times. Gut the electronics out of the baby Orcon, and hook it up to an external rectifier. It works really well, as the optics of the Orcon are not at all bad if in good condition, the weak point was always the electronics.

If you go down this path, you MUST preserve a; the operation of the fans, b; the air paths. I had a hell of a time with a pair of lamphouses 'converted' by another company in the UK. They had ripped out all the air tubes and the cinema found that lamps were lasting just a few hundred hours.