CP750 level drop disease

[Mark Gulbrandsen]

Replacing the CP750 motherboard is kinda silly in my opinion. The board costs greater than half the price of a new CP anyways

The capacitors to re-do the motherboard cost less than 20 bucks!

[Randy Stankey]

The cheap-ass television that I bought at fire sale prices from H.H. Gregg, just before they went bankrupt has lasted longer than some of these pieces of expensive, professional audio equipment.

I have worked in manufacturing electronics. If you have ever bought a VitaMix blender, I might have helped to make the circuit board inside. If you have been in a hospital that uses defibrillators made by Siemens or GE, I might have made that, too. Let me tell you, when you are making equipment such as that, you often have a supervisor proverbially standing over your shoulder every minute. Life in an electronics shop can be a bitch!

So, I'm sure that you can understand why I feel pissed off when I hear that professional audio equipment doesn't last as long as the cheapo TV I bought at a Going-Out-of-Business Sale.

Yes, I understand some of the things about cost of manufacturing... IPC Classes and all that.
Yeah, I know that we shouldn't expect every piece of electronics to pass military level scrutiny, every time.
I get it! If we had to make sure that every single circuit board underwent quality inspections to Six Sigma qualification, we'd be paying ten times as much. That's not a problem.

If everybody just "knows" that Dolby CP 750 motherboards "just fail" when they get old, there's something wrong!

[Carsten Kurz]

There is also still Datasat... We've been using an AP20 for years and never had some real issues with it. Most places I know never had a single show lost due to a problem with their AP20.

Similar to other devices, the AP20 had some issues with power-supplies. However, as far as I know, they have improved that during recent years. Our's runs since early 2013 without any issues. Not even a quirk since it's installation. The AP20 power-supply is a more or less common industry-standard OEM type.

For the amount of CP750 in the field, the failure rate may still be adequate. Still, the fact that practically, you have to buy two units in order to use it over an assumed 'typical' lifetime doesn't speak for Dolby. Our CP65/DA20 combo is now nearly 25 years old and never had any issues. I wouldn't demand the same from todays digital devices, but 10+ years should be doable for professional equipment in that price range. As a CP, it is also a single point of failure for every cinema. Not every site can afford to store a replacement on site.

- Carsten

[Leo Enticknap]

The AP20 power-supply is a more or less common industry-standard OEM type.

Hmm ... we had them when I worked at the Egyptian (2014 to '17), and had the power supply die in two out of the three units. I remember that there was something unusual about them (15v rather than 12 on the main bus, maybe?) that made it impossible to buy aftermarket replacements: the only practical way to get hold of them was from Datasat themselves. I have only encountered one AP20 in the three years since (and even then I didn't have to work on it - I was servicing other equipment in the booth), and so my memory of the specifics of them is a bit hazy.

The cheap-ass television that I bought at fire sale prices from H.H. Gregg, just before they went bankrupt has lasted longer than some of these pieces of expensive, professional audio equipment.

Maybe because your TV doesn't receive anything like as intensive or punishing use as a typical CP750? Powered up for 2-3 hours a day in an air conditioned living room is kinder than 24/7 in a projection booth with an ambient temperature well into the 80s. To which I'm guessing you'll reply that given the cost of the unit and it being a single point of failure in a theater system, Dolby really should have thought of that and designed accordingly.

I do wonder if the lack of a cooling fan in the CP750 is at least part of the reason why it has these two significant vulnerabilities (level drop disease, and the power supply boards crapping out). Maybe if they'd cut a grille into the power supply side of the case and put, say, a 60mm PC fan in it, that would have extended its life. The ones I've had go have tended to be in warmer than average places.

If you have ever bought a VitaMix blender, I might have helped to make the circuit board inside..

Besides traffic signals, what can be changed from green to red at the touch of a button?

A frog in a Vitamix.

[Marcel Birgelen]

[QUOTE=Leo Enticknap;n4901]Hmm ... we had them when I worked at the Egyptian (2014 to '17), and had the power supply die in two out of the three units. I remember that there was something unusual about them (15v rather than 12 on the main bus, maybe?) that made it impossible to buy aftermarket replacements: the only practical way to get hold of them was from Datasat themselves. I have only encountered one AP20 in the three years since (and even then I didn't have to work on it - I was servicing other equipment in the booth), and so my memory of the specifics of them is a bit hazy.[QUOTE]

Like Carsten mentioned, some of the first generation had flaky PSUs, they usually could be revived by replacing a few bad caps though. AFAIK it's indeed a pretty standard OEM PSU. Designing good PSUs isn't easy. I remember reading the articles on Folklore.org, written by early Apple employees, about the development of the first Mac. Even they hired someone externally, specialized at developing PSUs because they correctly recognized that building GOOD PSUs isn't as easy as it seems.

The capacitors to re-do the motherboard cost less than 20 bucks!

Keep in mind that not everybody is a soldering-iron ninja. My soldering skills for example, could be much better. I spent more time at re-doing the caps on the CP750 motherboard than what it probably was worth, but it became something of a pet project. Also, there is no real guarantee yet, that re-capping the board will solve this actual problem.

[Randy Stankey]

Maybe because your TV doesn't receive anything like as intensive or punishing use as a typical CP750? Powered up for 2-3 hours a day in an air conditioned living room is kinder than 24/7 in a projection booth with an ambient temperature well into the 80s. To which I'm guessing you'll reply that given the cost of the unit and it being a single point of failure in a theater system, Dolby really should have thought of that and designed accordingly.

Yes, you're right. I would reply that my TV is on for up to 12 hours a day or more but that's a special case. It's not fair to infer from the specific to the general, saying that my TV stands up to seven years of continuous use and that means all TVs should do the same.

Still, a cinema sound processor is mission critical equipment. It should be built to appropriate standards for such equipment. A few years of continuous use, even if the temps are over 80 deg. shouldn't cause problems like this. It's something else. Bad parts? Improper settings of the reflow machine? Poor workmanship? "Escapes" from the Q.A. inspections and testing?

The only thing, I shudder to think that Dolby cheaped out and produced product to consumer grade standards instead of industrial.

I work for this company:

Not that location, of course. I work at another factory located in my home town.
I'm not in that video but the room where I work looks just like the clip at 1:25 - 1:30 in that video. I could be one of those people sitting at those workstations.

We make cables and connectors that go into industrial equipment and aircraft like Boeing 747's and stuff like that. Just this evening, I sat, for eight hours squirting potting compound into D-Subminiature connectors. The whole damned thing is about an inch wide and it has 25 terminations. You do it with a hypodermic needle, looking through a 10-power microscope.

You can not get even one drop of stray potting compound outside the potting well of the connector. The pin height is measured to 0.001" and they have to be set between .005" and .035" but the spread between the highest and lowest pin can be no more than .0100"

If I pot one of those bad pins in place and it is out of spec, even by one thousandth, it gets returned to me with a red tag on it and I have to dig out all that cured potting with a heat gun and an Exacto blade, reset the pin then pot it all over again.

Every hour or so, a supervisor walks the line asking, "How ya' doin'?"

Just last week, when Air India Express Flight 1344 skidded off the runway and killed a couple dozen people, I said to my supervisor, "I hope none of my parts were on that plane!" He laughed and said, "I've been saying that for the last twenty years!"

I go through this kind of crap every day. Can you imagine how I feel when I hear that a movie processor just stops working for no apparent reason?

I struggle to pay rent, every month. This kind of mistake just makes me want to spit!

Besides traffic signals, what can be changed from green to red at the touch of a button?
A frog in a Vitamix.

Ouch!

[Mark Gulbrandsen]

Still, a cinema sound processor is mission critical equipment. It should be built to appropriate standards for such equipment.

Absolutely correct Randy! I have yet to see any cinema processor that has 105 deg C electrolytic capacitors installed in it, yet they don't cost but a few cents more per capacitor. I always rebuild boards with 105 deg C rating caps. Broadcast equipment typically always has them included.

[Steve Guttag]

The cheap-ass television that I bought at fire sale prices from H.H. Gregg, just before they went bankrupt has lasted longer than some of these pieces of expensive, professional audio equipment.

HH Gregg filed for bankruptcy in 2017. Is anyone having CP750 issues from units shipped in 2017 or later?

We have CP750s now over 10-years old without issue. Seriously, of the units we've sold/installed (so i know their racking environments), we've had zero motherboard failures. I think we've had maybe 5-6 power supply failures. The power supply issue was identified so they shouldn't be failing anymore. Apparently, the manufacturer of the power supply (not Dolby) got a bum run of a particular part that would fail. How rampant it is, I cannot say since, again, out of hundreds of units, we are up to 5-6...still a bit high as that is up to 3% or so.

Now we HAVE sold a few motherboards and quite a few power supplies to others. All of the theatres/complexes we installed, have a backup supply since it is quickly plugged in.

I did, accidentally, omit the AP20/AP25. My only concern about it now is that its design is getting along in years and I don't know how much vested interest ATI has in keeping it going. If I had a bunch of them out there, I'd have a better feel for what their state is. I don't think I know of anyone that has them that doesn't either like them a lot or, at least, have respect for them. I'm sure there are other processors out there that got omitted.

I don't know what you have against the JSD series.

I don't have anything against them, per-say. I was never a big fan of the JSD-80. I never liked its sound quality as a film processor and as a digital processor, it is frustrating with a single delay possible so DVD/Blu-ray and DCP can't be in lip sync...so, you have to adjust Blu-ray lip-sync in the JSD-80 and then adjust DCP lip sync in the server to account for both projector and whatever you're using for Blu-ray latency. I do allow for that it was a processor built before DCinema so it was caught off-guard, like the CP650 for DCinema and was pressed into use as a DCinema processor. There are other aspects of the JSD80 that I don't like (the fader commands use a bastard HEX over ASCII thing). I also haven't had the failure free success you've mentioned. But these are personal findings, you are welcomed as many others to find them to be great processors.

The JSD-60 has two things in particular that rub me wrong...it's missing 2-channels. I've almost never installed a 5.1 theatre once Surround EX came out. It isn't that I installed Surround-EX but that I wired the surrounds and amplified them that way. We use QSC DCA amps almost exclusively and the DCA 1824 just made it too easy and economical. The other one is almost inexcusable...the prologic decoder was put on pair 4 of the AES inputs. So, you can either have a-standard wiring with a-standard configurations or effectively not have that feature. We've used them for Drive-Ins were they've done just fine.

The JSD-100...if it had the features of the JSD-60 in it would have been a better unit but other than that...what does it bring to the table? 16-channels of AES? I can get Surround 7.1...fine...how bout handling a 2.0 soundtrack with a pro logic decode? It has an Active Matrix decoder...for 2-channel inputs (analog or digital) but what about DCPs coming in on the 16-channel input? Don't get me wrong, the JSD-100 has stuff going for it...it has quite a few inputs, both analog and digital. It just doesn't check the boxes I look for in a CP. It is sort of like the CP850 and the CP950. They have this glaring defect that we are asked to provide all of the time. The CP850/CP950 don't have a multichannel analog input...I use those..a LOT. Consequently, I've never sold a CP850 Base...you go down the list of features needed...no analog input...next. I found myself using the QSC DCP300 (and DCP200) for much of what the JSD-100 would have been considered for. It has an 8-channel and a 6-channel analog input so sources like "film" and "Video" can be accommodated at the same time...and since we use DCA amplifiers, it sort of fit the bill. The DCP line is far from perfect (again...nobody's perfect) but when looking at features needed/available, it would beat out the JSD-100, consistently. And now, with Q-SYS, particularly with the introduction of the DCIO (-H), you don't get much more flexible than drag-n-drop DSP. The baby processor (CORE) can handle up to 128 inputs and outputs...that should tide most people over for awhile.

[Scott Norwood]

I'm kind of with Randy on this, but I can also see where some elements of the computer industry are coming into play here. No one makes computers to last 10+ years because there is no real point to doing so, outside of certain industries (aerospace, military). Since a modern cinema processor is basically a computer with some analog bits added onto it, I can sort of see where that mentality would come from, although a cinema processor is an appliance with a fixed set of features and upgrades really shouldn't be needed for years, unless the requirements change.

I do wish that more stuff would just use regular PC-style ATX power supplies. This sort of device is a solved problem; good manufacturers (Seasonic, etc.) churn these out in large quantities with a very low failure rate. if they ever fail, they can be replaced inexpensively with locally sourced parts. ATX-size redundant power supplies are available, too (as used in the Doremi servers). I'm not sure why manufacturers insist on designing their own power supplies at this point if they can do what needs doing with +3.3V, +5V, +12V, and -12V.

[Harold Hallikainen]

On the CP750, it would be interesting to know exactly what is failing. An entire board replacement seems a bit extreme, though there may be another part just waiting to fail.

Switching power supply design is a real art, and there are specialists who just do that. Between the magic of magnetics, the high voltages, high currents, and high temperatures involved, it's real tricky! My switcher design has been limited to low power, low voltage stuff (POE in LSS-200, boost regulator in CCR-100 and CCH-100, buck regulator in IRC-28C). I THINK the switcher we bought for use in most USL products (JSD and other rack mount equipment) was pretty reliable. I don't remember hearing of a failure. However, the external 32 VDC power supply for the IRC-28C seems to fail right around the rated MTBF. I did not get an opportunity to see what actually failed in them.

Again, it's always interesting to know if a particular component is failing and why.

Harold

[Steve Guttag]

Scott, on the CP750 power supply...it isn't a Dolby design. Most people don't design their own switching power supplies for a component like a sound processor. As Harold pointed out, there is a real art to it...including keeping its noise out of the analog circuits (most of the CPs end in analog). I also think that the failure point on the CP750 is not likely designed in but something that didn't show itself for many YEARS and was a failing of a particular component...quite possibly capacitors.

As for changing an entire board versus component level work. SMT components put the hurt on doing component level service. It isn't that it cannot be done but it changes the skill level a bit and, when it comes to repair, the time/cost of the technician doing the work has to be factored into the cost...not just the parts. It is one reason a manufacturer can do such repairs, often cost effectively...they can be tooled up and the tech is going to be well experienced with the repairs. My guess is that the volume of CP750s are such that it isn't worth setting up repairing motherboards versus the cost of a new board, particularly during the warranty period.

As for the UPC28c power supplies...the first set definitely have a limited life...the current ones seem to be doing much better. And, again, one has to be careful about noise with analog things (the UPC28c has analog inputs) so not just any switching power supply with the right voltage is going to work as needed.

[Randy Stankey]

No one makes computers to last 10+ years because there is no real point to doing so, outside of certain industries (aerospace, military). Since a modern cinema processor is basically a computer with some analog bits added onto it, I can sort of see where that mentality would come from, although a cinema processor is an appliance with a fixed set of features and upgrades really shouldn't be needed for years, unless the requirements change.

I looked up the price of a CP750 and found out they cost around $3,500, plus or minus 3 dB. It was probably a base model, too.

You know... That's half a year's rent for me!

Okay, for a big corporation like Cinemark, etc., that's like me reaching into my wallet and pulling out a $20 bill. It's not that expensive but it's not peanuts, either. However, when you have 500 theaters (worldwide) and each site has an average of 10 screens (some older locations only have 3 screens and newer, megaplexes have 20 or more) you're looking at up to 5000 cinema processors to buy, operate and maintain. That money adds up! ($17.5 million)

For that kind of money wouldn't you want to buy equipment that's going to last? Don't forget the cost of having a screen go dark.

I have yet to see any cinema processor that has 105 deg C electrolytic capacitors installed in it, yet they don't cost but a few cents more per capacitor.

When I worked as a machine loader at an electronics shop, making PCBs, there was this incident where we had three different jobs that all used the same 2N2222 transistor but we only had one reel of parts. We spent over a week, shuttling one reel, back and forth, between machines just to keep jobs running. It was a big fluster cluck!

I got fed up and Googled the part and found out that a reel of 10,000 of the things cost less than $150!

It was a few weeks later that they laid off the entire second shift due to lack of parts in the stock room.

What? They shut down the shop because they couldn't buy a couple of reels of "chicken feed" parts?

At 1.5¢ per transistor, they could double the cost of those parts and still make good profit without raising the price of the product very much, if at all.

How much extra would you be willing to pay for a processor if it had 105 C capacitors in it instead of the others if you could be assured that the thing would be a lot less likely to fail? 5%? More? Less?

Isn't it worth it to pay a few bucks more, in the short term, if you will have to spend less time fixing things when they break or replacing them when they stop working?

BTW: Replacing Surface mount components on a moderately complex board isn’t THAT hard. I have done it using nothing more than a soldering iron, a magnifier and a pair of tweezers. Rework stations in a shop do it that way on a daily basis. For more detailed work they use hot air machines. It is well within range for a technician of average skill to perform repairs in the field if he is trained. A person can learn to do it in an afternoon if they have a good teacher.

[Carsten Kurz]

I think some manufacturers simply settled on the idea of a 10 year lifecycle for digital cinema gear, and then releasing a new model with 'some' improved featureset. So, there is no big incentive to build gear that lives longer. Saving money by not using hightemp caps is a win-win for them.

[Steve Guttag]

Randy...a few things. On the CP750 price...you're off by about $1,000 (not necessarily on the list price but on real-world prices. The cost of the motherboard is going to be about 1/2 the cost of a street price CP750.

As to the cost of parts...you can't isolate one part like that but you would have to make the same questions to all of them and then, suddenly you aren't talking about a few cents but you are now into dollars or hundreds per finished unit...which either has to be eaten as lower profit or passed on as a more expensive product, which, particularly in this industry, will result in lost sales.

I, again, come back to I don't think that whatever is failing was designed into the CP750 but was discovered long into the production and may not even exist on current motherboards.

As for exhibitors paying more for a product just because it should last longer...not in my 40-years in the biz has that been a selling point to the overwhelming majority. First off, it is almost always impossible to back up. If you sell a product claiming 15-20 year service life and it dies on year 11...or 5 die on year 11 but 200 keep going...who of that original transaction are still players for the companies with each other? Even overall quality can have little bearing on the sale. If it did, USL and Smart, and Kintek and the rest would never have had any market versus Dolby on cinema processors. None of the off-brands could track the Dolby NR, had the service life or the quality built into their CPs as Dolby did (particularly when comparing in the analog days). That was price and politics that drove those decisions. It was the same with projectors...you'd never see a Film Systems package sold if it was just based on quality and longevity...yet there they were...with quantity. About all one can go on with respect to longevity is going to be the history of the company, not so much a particular product. Why would people by a projector company's IMB nowadays? What is their history making "mediablocks?" And yet Christie and Barco make their own and package them right along with the projectors. The reliability of those mediablocks don't hold up as well as the 3rd Party ones but, naturally, 3rd party ones cost more than the house-brand and the projector company can (and do) build in "hooks" to give their product a control edge.

As for servicing CPs, in the field at the component level with a quantity of SMTs? That is going to happen less-and-less and it doesn't happen now. It isn't cost effective. You are comparing the time it takes for a technician to swap out an entire board plus the cost of the board versus pulling/installing the same board plus the time of changing the suspect components in a steamroller approach to repair (change all electrolytics in the hopes you get the one or group that are causing the issue). So you better have a fast technician to make it worthwhile...and...when done, they still have a 10-year old board in there. Part of what made Dolby processors great back when they came out (talking 70s and 80s) was you didn't need to do field repairs like that...you merely RXOed the board and swapped it out and leave the component level work to the proper test bench with the proper test equipment to ensure it is in spec when done. BTW...that cost was cooked into the processors price...there wasn't a charge for RXO boards except the freight.

If the parts for the CP750 MB are known...it is probably worth it to have someone take replaced MBs and change out the electrolytics and have their own stack of MBs for future swaps...now that could be cost effective but never would I have that level of work done in the field. When you are done in the field, the unit has to work.

[Dave Macaulay]

I'm not convinced that capacitor failure is at fault for the level drop.
Dolby has never published the signal path for the 750, let alone a schematic. It's pretty much impossible to troubleshoot a multilayer SMT board without a schematic and a boardview. I don't know if there's a spec for output voltage with alignment signal and specified channel fader level.
10 years is pretty decent life, really. I expect to drive a car for 10 years now (up from a "maybe" 5 years for 70's cars) but also expect some (hopefully minor) components to fail in that time. Older electronics with through-hole components like amps are usually serviceable but a schematic is super helpful - even without one bulging/leaking caps, exploded transistors, and charred PCBs guide diagnosis.