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This topic comprises 4 pages: 1 2 3 4
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Topic: Optical Sound Troubleshooting Help
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Tony Bandiera Jr
Film God
Posts: 3067
From: Moreland Idaho
Registered: Apr 2004
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posted 07-26-2009 01:31 PM
Victor and Scott, thanks for your support on this. Some people cannot be convinced that there are other and sometimes better ways to troubleshoot problems. Perhaps the methods they use have worked well for them, but then again they may not be on the clock and expected to get to the bottom of a problem in the shortest time possible, and without making a lot of incorrect guesses.
When dealing with ANY troubleshooting, it pays to look at the WHOLE picture to help pinpoint the actual cause of a problem. The time spent looking at the whole picture is a LOT less than the time wasted chasing a wrong diagnosis and repeat service call. For example this, which was a 4-hour(!) call which, had I applied a bit more logic from the start, could have been found in 20 minutes:
quote: Me a few posts back
Example of unusual cause/effect: Customer had a CP-200 that would randomly switch to Format preset "D" (set for non/sync in that case) with no thumps or other drop-outs in the sound. After disconnecting the automation connection (rules out automation issue), pulling and re-seating ALL of the cards (rules out bad connection at the cards), pulling, inspecting and re-seating the power supply DC bundle (rules out bad Molex connections/loose pins) the problem persisted. What I eventually found, was that in the rat's nest of power cords (ALL the plug ends were cut off and tied in by a terminal strip) that the neutral on the CP-200 power supply cord's screw was loose. Tightened up the screw and no more problems. The loose connection would interrupt the power just long enough to fool the logic circuits into thinking the processor was powering up, but not long enough to make a thump in the sound. I found the bad connection when I kicked the rack in frustration. ![[Big Grin]](biggrin.gif)
In Martin's case, yes it turned out to be a mechanical issue, which WILL show as higher error rates in Digital. Had Martin mentioned or noticed that, it would have led to a quick pinpointing of mechanical trouble. BUT, let's say the Digital errors were running at 1-2 or 3, but the analog sound was a mess. NOW we can say let's focus on the analog part ONLY, as now the trouble could be:
Bad optical lens focus;
Oil in the optics (good call Mark);
LED for analog bad;
Power supply for analog bad;
Electronics for analog bad;
"A" Chain needs adjustment.
Demetris mentioned the following:
quote: Demetris Thoupis
If the drum was not spinning correctly I am sure Martin would check all that is necessary to fix it and that was the case.
I agree with that, BUT: how many people can look at that drum and see it's not spinning "correctly"? With the flywheel loose it may, to the inexperienced eye, APPEAR to be spinning correctly. Only if the bearings are grossly tight or some other issues cause it to spin VERY erratically the average projectionist will NOT be able to tell that it is the problem.
And if it was so obvious, I doubt Martin would have asked us for help, he would have perhaps made a "Did this ever happen to you" kind of posting.
quote: Demetris Thoupis
Hmm so when there is no sound in the auditorium I need to take the ladder and check first if a speaker cable is out, then go back to the amplifiers to see if the cable is out, then see if the signal cable from the amps to the processor is damaged and THEN check if they are off!! Hmm does not sound like a good advice to me. Sorry but his point clearly mentioned analogue sound. Someone saying that analogue has a problem means that the analogue has a problem! .....
Now that's the kind of smart-ass attitude I was talking about. You need to open your mind and close your mouth a bit and you'll find a lot of things that you don't know, just like I have found out after 26 years in this business there are LOTS of things that I don't know!! Why do you think I have continued this job for so long? Because I like encountering new things and situations and when the day comes that it gets to be routine that's when I'm retiring. You can ask other techs here on F-T and find out that I have asked questions to get to the bottom of something I couldn't figure out. It's all part of the learning curve.
Oh, and by the way, on the screening room I'm currently updating for D-Cinema, the HF horn for the left channel was out. AFTER checking the processor, crossover, amp and yes the cabling connecting to the amp, the problem was simple: someone had stepped on the cable backstage and pulled the wire out of the driver's terminals. And yet I STILL fell into the trap of ASSUMING at first that the driver was blown out. Good thing I dug deeper before ordering the parts.
quote: Gordon McLeod
I think two people need to take a valium
they are many methods of troubleshooting and often the equipment type or common method of installation in a given region needs to be taken into account
LOL as for the Valium, I don't need to, I don't get riled by people I don't know. ![[Smile]](smile.gif)
But yes you are absolutely right, there ARE many methods of troubleshooting and yes region and equipment play into it. BUT a basement reader here in California and a basement reader in other parts of the world will still operate on the same basic principles and the same logic to find the trouble apply.
It still boils down to looking at the WHOLE picture to help narrow down the possibilities. As I said above, IF we could have proven that the Digital in this case WAS "fine", with NORMAL LOW ERROR RATES, then of course the cause of the problem would NOT have been the mechanical issue that Martin had.
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Monte L Fullmer
Film God
Posts: 8367
From: Nampa, Idaho, USA
Registered: Nov 2004
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posted 07-26-2009 11:50 PM
quote: Tim Reed
but some people think that if a pilot lamp is lit, the device is working.
May I borrow an incident from a movie that had this similar situation:
How many of us remember Universal's "Patch Adams?" There was a section that one can take heed from that really holds true-which also includes what Tony's coming across and from what Tim above quotes:
Remember the scene where the one patient had "Patch" hold his hand to his face and ask him how many fingers he could see? Course, the answer was obvious 4 fingers..and the patient told him that he was wrong. Moving towards the movie, the patient had him do the same test again, this time "Patch" could see more,and the patient told him that he was right...
People, in general, only see what's in front of them (like if the bulb is lit, everything is okey..as what Tim mentions), but if we can see "past our noses" - "past the okey" - then we really can see what we really need to see.
Here's an example that happened to a fellow worker of mine: He comes back from the shop from having his car worked on since he had mentioned of a strange engine noise and an oil change. It still has the noise and the shop told my friend that he's looking at major engine repair bill.
Out of my curiosity, we went out to the car, he started it up and there definitely was the noise. I told him to stop the motor and I pulled the dipstick - bone dry. I then asked my friend, "didn't they change the oil as requested?" I went to the local quickcare auto parts place, bought a 5quart container of oil, shoved it down in the oil fill which got the oil level up on the dipstick, he started up the car and the noise was definitely gone.
I then told my friend to go back to that shop and raise some hell on this one...which he did.
Case in point: shop heard the noise and said 'motor repair' (even though I'm sure it was planned that way so they could earn his business back....), I went farther and with a simple check found the problem being no oil in the crankcase.
I also agree with Tony: being a tech is a continual learning experience, sometimes on a trial and error basis (which is actually good for us for that helps up to really remember what we experienced) - we never will get all the learning that we always need since it's always changing..
quote: Tony Bandiera Jr was the last to post
Only if the bearings are grossly tight or some other issues cause it to spin VERY erratically
May I borrow this statement as well: Thx to STRONG not having pressed in bearings on their 5-star units, how many of us seen grooved out scanner drum shafts due to bearing failure, yet the scanner drum still rolls smoothly in the normal eye? Why, when I do belts on the 5-star units, I spin both the scanner drum shaft and the main drive shaft with the flywheel/pulleys off so I can check these bearings out.
-Monte
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