Film-Tech Forum ARCHIVE: CP 750 problem

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Posted by David J Hilsgen (Member # 2614) on 08-21-2019, 02:48 PM:

I've had a few CP 750 s go dead where even the backup power supply does no good. I've noticed the 5 amp Auto fuse had blown on the circuit board ,replaced that get a few flashes from the front that's it .has anybody else had the same problem and know what's causing this.

Posted by Ken Lackner (Member # 1002) on 08-21-2019, 05:08 PM:

Yep. Not exactly sure what causes it, but I suspect heat, as those things have no active cooling and they get very hot. The only thing that can be done at this point is replace the motherboard. You can purchase one from Dolby or send your unit to them for repair. Sorry, wish I had better news.

Posted by David J Hilsgen (Member # 2614) on 08-21-2019, 10:16 PM:

Yeah I bet if a guy would take that top cover off cut a square hole into it Mount a fan in there it probably would prolong the life

Posted by Marcel Birgelen (Member # 6801) on 08-22-2019, 01:24 AM:

quote: David J Hilsgen
I've noticed the 5 amp Auto fuse had blown on the circuit board ,replaced that get a few flashes from the front that's it .

It's a clear indication whatever caused the issue isn't gone. If you do have backup power, maybe you can disconnect that one after replacing the fuse to make sure that one isn't actually the culprit.

Also, if you do have backup power, you could try to run it on backup power only, by disconnecting the main power from the motherboard (connector on the "bottom right" when you have the front plate in front of you), this to ensure that the main PSU isn't the problem.

If that doesn't help, it's probably a component on the motherboard gone wrong.

Posted by Mark Gulbrandsen (Member # 72) on 08-22-2019, 10:30 AM:

Makes me really glad I went with USL at all my DC conversion sites over the years. I have not had any JSD-100 failures yet. Have had two JSD-60's go kerfluey on me though.

Mark

Posted by Steve Guttag (Member # 268) on 08-22-2019, 09:35 PM:

Hmmm. I believe all of our CP750s are still going too. I think we've had 3 power supplies fail (could be a couple more but not many). We also give them space above/below to breathe.

I don't get the point of the JSD100 and the JSD60 was just 2-channels shy of where it needed to be. The JSD60 also put the pro-logic decoder on the wrong AES pair. Near-misses.

Posted by Mark Gulbrandsen (Member # 72) on 08-24-2019, 07:25 AM:

No Idea on that because all my JSD-60's are in simple 5.1 systems that never play back anything through pro-logic. The user programmable mix down matrix is also very handy for drive in use. For a small processor/price point it has a lot of features that others lack. Auto-EQ, Parametric EQ, and an optional three channel biamp crossiver just to name a few.

Mark

Posted by Steve Guttag (Member # 268) on 08-24-2019, 10:21 AM:

Most of our systems are 7.1, hence the missing 2-channels. And since they have a matrix decoder...it SHOULD have been on pair "A" to handle DCPs that have a 2.0 channel configuration (shows up more times than I care to mention).

Agreed on its drive-in configuration...where we also use them. Note, there is yet more configuration available on the JSD-60, if one looks under the hood. Like you can decide which channels respond to the fader or not so you can set up your drive-in, in particular as you see fit. There is a lot right about the JSD60...just missing 2-channels and the matrix on the correct channels, for me.

Posted by Mark Gulbrandsen (Member # 72) on 08-24-2019, 01:20 PM:

Only four out of 340 screens I did got 7.1 installed. Three were with JSD-100's and one was with a QSC Cinema processor. At that site we were able to gut the theater equipment wise and start over from scratch. Most locations were too small to justify it, or they just didn't want to spend the money to do it. In fact at Mike's theater, QSC actually advised against it because of the size. Most of my customers screens were <200 seats.

Mark

Mark

Posted by Marcel Birgelen (Member # 6801) on 08-24-2019, 06:48 PM:

In my opinion 5.1 to 7.1 is a bigger upgrade than 7.1 to Atmos for most environments.

In our screening room, most people are capable of hearing the subtle differences between a 5.1 and 7.1 mix. It really adds some "physical depth" to the sound as you can clearly indicate sounds as coming from behind you.

Then again, most people don't really hear the difference between Atmos and 7.1. If you really play them one after another and you specifically point at the differences, you might see that some of them notice them, but even for me it's often hard to hear and you could easily fool me by just claiming something to be an Atmos mix, where it actually isn't...

The biggest advantage of Atmos is that we do have 5 stage speakers and that format could actually use them appropriately. Unfortunately, most Atmos mixes still locate dialog just flat in the center, probably simply in the center bed because they're simply to lazy to let it track the location of the character on screen...

The overhead speakers are there just mostly for the show. I wouldn't even mind if they'd scrap them from the "minimum equipment list".

Posted by Mark Gulbrandsen (Member # 72) on 08-24-2019, 08:27 PM:

Which is why I never have advocated Atmos. Just as 7.1 is expensive, the expense for Atmos is extremely hard to justify in a 250 seat room. And even going from 5.1 to 7.1 is going to involve redoing the wall coverings. Its that part that made most customers shy away. There is usually more expense there than in the actual surrounds.

Mark

Posted by Ron Curran (Member # 3631) on 08-24-2019, 10:16 PM:

7.1 was a breeze for us because we already had it for film. I really don't know why 7.1 AND Scope didn't become the standard for DCI. The system could easily cope with a fallback to 5.1. And cropped formats are a no-brainer within a Scope container.
Also, I can't see the value of Atmos when 7.1 is still a rarity. Especially if your main market is not Action-adventure pix.

Posted by Steve Guttag (Member # 268) on 08-25-2019, 08:53 AM:

7.1 is essentially a zero cost upgrade. MOST of the systems I dealt with already separately amplified the rear surrounds (EX or not, in the film days). Hence most of our systems are 7.1. It didn't cost ANYTHING. I don't think I upgraded many/any from 5.1 to 7.1. There were some 4.0/4.1 to 7.1s though and a few 1.0 to 7.1 (going from film to DCinema).

As for new installs, they are almost all 7.1. It has to be the odd room that would only get 5.1.

Size of room should have ZERO consideration of 5.1 versus 7.1. Shape of room, on the other hand, could have an impact. If it is 100-feet long and only 20-feet wide, then 7.1 will have little impact for many and would require quite hefty speakers for the rear surrounds (say QSC's SR-1590s or JBL's 9350s).

And, for the record, I've never had QSC try to talk me into or out of a product/design. Who is the designer? You or them? If I have a question about a product's appropriateness, I'll ask them...not wait for them to tell me. You are supposed to be the one with the knowledge.

Posted by Mark Gulbrandsen (Member # 72) on 08-25-2019, 10:58 AM:

I don't remember who the designer was back then (2012ish), but that same person highly reccomended it at the large single screen where we had already planned on doing it. Most of the systems I delt with were installed by others in the stereo optical days. When a chain has 90 out of 115 screens equipped that way, the upgrades, if they are done, happen over time. And that chain has since been sold. So who knows what has happened there. Again, you are over looking the cost of re-doing the theater wall coverings. Wooden backings were typically put on the wall first and coverings went over those, so they'd have to be moved and some new ones added for extra surrounds. The cost of the interior coverings had to be taken into account in the overall cost of going to 7.1 in all the locatons I serviced, and that cost is higher than the conversion to 7.1 itself. Older locations coverings are going to be not only filthy, but probably faded just from atmospheric exposure over 30+ years. Having seen the dust come off of old wall coverings liek that being removed in those sorts of places, I prefer not to even be in the same county when that is going on.

Mark

Posted by Steve Guttag (Member # 268) on 08-25-2019, 11:19 AM:

Why are they needing to add speakers to the rear wall? They should be there already in a 5.1 system! That is why 7.1 is essentially a zero cost upgrade. At most, one would need an additional amplifier and reconfiguring the surround wires to the amp, if it is a 5.1 system.

If they don't have rear surrounds in a 5.1 system, they are doing it wrong already.

Posted by Mark Gulbrandsen (Member # 72) on 08-25-2019, 11:22 AM:

Oh there were in SOME places, but in the wrong locations and would have to be moved and or added to. Most were originally very poorly done installs to begin with that went in way before 7.1 was even a glimmer of light in someone's eye.

Posted by Jarod Reddig (Member # 6363) on 08-25-2019, 05:05 PM:

I agree 5.1 to 7.1 is a bigger more noticeable upgrade then 7.1 to Atmos.

Posted by Victor Liorentas (Member # 5272) on 08-25-2019, 06:47 PM:

The first and maybe only time I heard Dolby Atmos was on Gravity.I was blown away!Ever since that time I have noticed no Atmos effects on any movie. The Force Awakens sounded like 7.1...the last Terminator sounded like 7.1
I then started looking into it and learned that their processor was reverting to 7.1 due to normal neglect.Need rebooting or whatever it takes but nobody cared to check unless someone complained (me)!

So maybe Gravity just used Atmos to it's full potential and maybe some Atmos units require some babysitting?

Posted by Mark Gulbrandsen (Member # 72) on 08-25-2019, 07:45 PM:

I have heard 13 Atmos films and only Gravity really impressed me. I get the impression that many of the Atmos systems being installed are just the bare minimum so they can get certified, put up the name, and charge the premium. It also seems that the mixes under-utilize it. I finally stopped going to Atmos shows.

Mark