750 replacing a dead JSD 60

[Laurence Hammett]

A client has asked me to replace a dead JSD 60 with a CP 750. The 750 spits sound correctly to auditorium but although 750 Sees the server no sound is passed through in spite of even going to DB 25 cables from the solaria projectors server. However when I hook up a D To A converter through a CP 650 all is golden. Am I missing something. I would have thought that the cable should work for AES-EBU to either JSD 60 or CP 750. Client bought the 750 used so it wouldn't amaze me if the unit was bad as I have had at least 3 others die within the last couple of years.

[Harold Hallikainen]

First off, I'm sorry to hear about the dead JSD-60. It was a lot of fun to design! The CP750 and JSD-60 DB25 AES/EBU inputs have the same pinouts, so that should not be the problem. I wonder if there is some configuration that is messed up. I have not done enough with the CP750 to be much help there. Good luck!

[Leo Enticknap]

Installing a CP750 now is really not a good idea, because of two known issues, the upshot of which is that it's a question of when it dies, not if.

The first, less serious one is that the power supply cards tend to go. I don't know if Dolby still has them, but the last I knew, we still had two or three in stock, plus a few used but OK ones culled from CP750s that had succumbed to the other, more serious cause of death.

This is nicknamed "level drop disease," the symptom of which is that the master output level drops to the point at which the CP750 is unusable. You end up maxing out the channel gains and setting the fader to 10, and you can barely hear anything. The unit also cannot be tuned to reference. The cure is replacing the motherboard, but because the factory that made one of the chips on it burned down during the pandemic and these chips are no longer available, Dolby can no longer sell replacement motherboards. So once level drop disease happens, it's the end of the road for your CP750.

I've found that typically, most level drop disease failures happen between six and nine years from the manufacture date on the sticker on the back. The cause is overheating, so CP750s in relatively cool racks can last a bit longer.

When you write "The CP750 sees the server," do you mean that you have a light below Digital 1, as so:

image.png
If so, do other sources and test signals play OK? If nothing plays OK, I suspect level drop disease. If other sources do play OK and you have that green light, the answer likely lies in the server settings. The green light indicates that the CP750 thinks that it's getting valid AES3 on all the channels it's expecting. If you do not have the green light, there is a problem with the input AES3 data.

The only channel routing/configuration options on the CP750 affect how the rear surrounds for 7.1 and HI/VI are handled:

image.png

Misconfiguring this setting relative to what is in your room would not cause the first six channels (left, center, right, LFE, left side surround, and right side surround) not to play.

[Mark Gulbrandsen]

First off, I'm sorry to hear about the dead JSD-60. It was a lot of fun to design! The CP750 and JSD-60 DB25 AES/EBU inputs have the same pinouts, so that should not be the problem. I wonder if there is some configuration that is messed up. I have not done enough with the CP750 to be much help there. Good luck!

I actually switched from Dolby to USL processors because Dolby had the capacitor plague pretty bad with the CP-650 and many died after just two to three years. Customers just did not want to buy any more Dolby products no matter how hard I pushed them. So... I installed lots of JSD-100's, and quite a few JSD-60's instead. Never had a single issue with any of the JDS's, but I've been out of the field since 2018, and who knows if they are all still running or not. I assume many still are.

[Scott Norwood]

What processor are people installing now for 5.1/7.1 DCP-only setups now? Is everyone doing Q-sys even for simple installations? Or is there some other high-value processor that people like now for this use case?

[Laurence Hammett]

What processor are people installing now for 5.1/7.1 DCP-only setups now? Is everyone doing Q-sys even for simple installations? Or is there some other high-value processor that people like now for this use case?

New for me is Dolby CP 950 but I hear TRINNOV is being pushed by some suppliers.

[Laurence Hammett]

I actually switched from Dolby to USL processors because Dolby had the capacitor plague pretty bad with the CP-650 and many died after just two to three years. Customers just did not want to buy any more Dolby products no matter how hard I pushed them. So... I installed lots of JSD-100's, and quite a few JSD-60's instead. Never had a single issue with any of the JDS's, but I've been out of the field since 2018, and who knows if they are all still running or not. I assume many still are.

I have always have liked USL processors and this is the only one I have had crap out on me. 750's are dropping like flys. 3 in one 6 plex.
What is upsetting is QSC bought USL and then killed it except for HI/VI closed cap which they farmed out to MIT.

[Laurence Hammett]

Installing a CP750 now is really not a good idea, because of two known issues, the upshot of which is that it's a question of when it dies, not if.

The first, less serious one is that the power supply cards tend to go. I don't know if Dolby still has them, but the last I knew, we still had two or three in stock, plus a few used but OK ones culled from CP750s that had succumbed to the other, more serious cause of death.

This is nicknamed "level drop disease," the symptom of which is that the master output level drops to the point at which the CP750 is unusable. You end up maxing out the channel gains and setting the fader to 10, and you can barely hear anything. The unit also cannot be tuned to reference. The cure is replacing the motherboard, but because the factory that made one of the chips on it burned down during the pandemic and these chips are no longer available, Dolby can no longer sell replacement motherboards. So once level drop disease happens, it's the end of the road for your CP750.

I've found that typically, most level drop disease failures happen between six and nine years from the manufacture date on the sticker on the back. The cause is overheating, so CP750s in relatively cool racks can last a bit longer.

When you write "The CP750 sees the server," do you mean that you have a light below Digital 1, as so:

image.png
If so, do other sources and test signals play OK? If nothing plays OK, I suspect level drop disease. If other sources do play OK and you have that green light, the answer likely lies in the server settings. The green light indicates that the CP750 thinks that it's getting valid AES3 on all the channels it's expecting. If you do not have the green light, there is a problem with the input AES3 data.

The only channel routing/configuration options on the CP750 affect how the rear surrounds for 7.1 and HI/VI are handled:

image.png

Misconfiguring this setting relative to what is in your room would not cause the first six channels (left, center, right, LFE, left side surround, and right side surround) not to play.

Turns out that the server is spitting out DCI but the 750 wants to see DMA 8 so I ordered a board from Dargco. Apparently they survived the hurricane. Thank god for my nifty box that spits out AES in both formats in tone, pink and channel ID.

[Laurence Hammett]

First off, I'm sorry to hear about the dead JSD-60. It was a lot of fun to design! The CP750 and JSD-60 DB25 AES/EBU inputs have the same pinouts, so that should not be the problem. I wonder if there is some configuration that is messed up. I have not done enough with the CP750 to be much help there. Good luck!

Actually the server is spitting out DCI but the 750 wants to see DMA 8. I do love USL products. Sorry they got bought up by QSC and then killed.

[Mark Gulbrandsen]

I have always have liked USL processors and this is the only one I have had crap out on me. 750's are dropping like flys. 3 in one 6 plex.
What is upsetting is QSC bought USL and then killed it except for HI/VI closed cap which they farmed out to MIT.

Seems to be a Dolby Tradition! But in all fairness, Cinema Processors rack up tens of thousands of hours really fast. The other sad part is so many are tossed just because of bad electrolytic capacitors. Generally caps rated at 85c have about a 7 to 10 year life expectancy, and 105c caps a few years longer. Re-capping a CP-65 power supply is pretty easy, takes under 2 hours, and I actually did them on site. But recapping an entire processor takes hours, and you need to have the proper de-soldering gear to do it properly. Also, some chains would rather replace as they can write some of the cost off.

[Leo Enticknap]

Sadly, the CP750 "level drop disease" is not a bad capacitor problem: it's a IC chip problem. The underlying problem is that everything is one one vast motherboard, so if one non-generic (i.e. not a capacitor or resistor) component can no longer be obtained, the manufacturer can no longer make new motherboards and offer them for sale. Combine that with a known weak spot with another non-generic component, and the entire unit becomes e-waste.

Like Larry, I've had customers faced with CP750s in their death throes buy supposedly "used but OK" CP750s on Ebay (and other sources), and have me swap them in, to kick the can down the road and avoid the more major and costly disruption of replacing them with another model. If they buy one for $500 and they get 2-3 years out of it, it could be an OK deal; but if I were a theater owner or operator, I wouldn't want that guillotine blade hovering above my head, knowing that the screen could be down at any moment.

I do love USL products. Sorry they got bought up by QSC and then killed.

In our defense, we bought the HI/VI/CCAP system from QSC and, with Harold's help, have been gently resuscitating it, including active work on the software/firmware, and hardware improvements including a new power supply brick that we hope will outlast the originals. But I fear that the JSD processors are essentially on their way out, now.

[Mark Gulbrandsen]

Well, even the IC's can be replaced as long as it's a generically available chip. SMT is pretty easy to do. I just repaired an old Parasound Zone Preamp for a friend. In his unit the micro controller failed. I know a retired HP Engineer that can download the stored program, then write it to a file he saves, then rewrite that file to new chips. I met him on another forum a long.time ago, because I used to have an HP Digital scope that sometimes refused to boot, or sometimes would not fully boot. The type of chips in that old scope were the kind that whats written on them fades over time. So I sent him the chips and he cleared them and rewrote the program, which he already had back on to them.
On the Patasound I sent the controller out of another working unit plus a NOS chip. And so he returned the NOS and the factory original. Both units work fine. So if the 750 is havimg micro controler chip issues, it still may be able to be fixed. Other non programmed chips if obsolete are always still available, just not in production quantities, and often from places that specialize in obsolete semiconductors.

[Harold Hallikainen]

Actually the server is spitting out DCI but the 750 wants to see DMA 8. I do love USL products. Sorry they got bought up by QSC and then killed.

I assume this is the pin out on the DB-25. The CP750 and the JSD-60 use the same pin out on the DB25 connectors. See http://ftp.uslinc.com/Products/JSD-6...06.pdf#page=71 and https://projectionniste.net/docs/dol...al.pdf#page=79.

I think this pin out was originally defined by THX. A later pin out (used in later USL products) is AES59-2012, which was originally defined by Tascam.

So, I THINK that the AES DB25 that was plugged into the JSD-60 should also be able to drive a CP750.

Both Dolby and USL used ADC and DAC chips from AKM. USL also used DIR/SRC chips from AKM. Their factory burned down, so the chips were no longer available. Looking at the AKM web site, I do see codecs and sample rate converters. The SRC I see does not include the DIR that USL relied on, so that may not longer be available.

To a certain extent, EOL parts can be designed around. The front panel PCB of the JSD-60 (or maybe it was the JSD-100, I don't remember) was redesigned at least twice to deal with displays going EOL. The firmware was updated to figure out which display was present, then drive it appropriately. Some parts, though, like the DIR/SRC may have no replacement thereby requiring a substantial redesign of an old product. At some point, it's just more appropriate to start over with a new design.

Harold

[Steve Guttag]

With respect to CP750s.

Power supplies are available. The internal one is available from Dolby and we do stock them from the OEM supplier. That said, I'm starting to recommend to avoid using the internal supply and, instead use an external one. This removes one of the heat sources from within the box. I'm even thinking about mounting fans in lieu of the internal supply to draw air across the components.

The OEM for the external supply (same as the internal supply but in a plastic case) is NLA from the OEM but Dolby has stock. We have source a suitable replacement from Mean Well (and we've never had problems with their power supplies, in general). One does have to remove the stock DIN connector in favor of the 4-pin XLR female connector. The Mean Well part is a GP50A14E-R1B.

Another bonus to the external supply is that the end user can change it without tools!

Leo, how certain are you that actual chip damage is happening to cause the lower output levels? Is there any chance that capacitors are causing rails to sag and result in lower levels?

To answer the question of what are people using for basic 5.1/7.1. I'd say that the bulk of ours are Dolby CP950s. QSC still has their DPM300/300H. These are at the lower end of the cost scale (think about that, Dolby is towards the lower end of the cost scale). Trinnov OV2 has its following and has the benefit of handling the voicing/tuning of the room. Moving up, the Datasat AP25 gets you a hybrid of DSP processor with automation capabilities (and some video switching). And then their is Q-SYS. We are using Q-SYS for 7.1 systems, for sure. But, generally, when we do that...it will be a pair of Cores running a complex rather than 5-10 individual systems. Many of our single-screen Q-SYS systems have Q-SYS handling automation, control, video switching ...etc. So, more than just sound. I think if you look at my Q-SYS Corner thread and the responses/participation (or lack thereof) you'll get a sense of how many people are using Q-SYS versus the bread-n-butter processors like the CP950.

Another faction, though I don't think it is all that popular, is to use the server itself as a 5.1/7.1 processor. The Dolby IMS3000 and the GDC SR-1000 have audio processor options.

Oddly, Harman/JBL has their own Cinema Processor, which I see in more non-US installation pictures than in US ones.

I had mixed results with USL sound processors. The JSD100 has been a bit of a tank. I don't know if I ever had a failure on one. It was a bit rough, at first on its Ethernet port. The first command was a throw away to open the port. But, for the most part, it just works. The JSD60 is 2-channels shy of where it needed to be. It needed 7.1 with HI/VI. Also, USL seemed to have issues getting good shaft-encoders as they often went bad (from the JSD80 onwards). While it was available, I was using the JSD60 exclusively in our Drive-In installations.

[Leo Enticknap]

Leo, how certain are you that actual chip damage is happening to cause the lower output levels?

This was the explanation given to me by someone from Dolby at a Cinemacon chat (don't feel comfortable giving a name on a public website), and I've seen no reason to question it further. Plus, if the cause were an easily swapped out generic component, one would expect Dolby to offer an RXO service for these motherboards, and/or publish details of the fix for those who are comfortable wielding a soldering iron in the field.

Another faction, though I don't think it is all that popular, is to use the server itself as a 5.1/7.1 processor. The Dolby IMS3000 and the GDC SR-1000 have audio processor options.

IMHO, the reason it's not popular is that there is no onboard DAC. The IMS3000 and the SR-1000 with audio processing enabled spit out either AES3 or AES67 (or a Dolby-ized variant thereof): no analog. So either the amplifiers need to have onboard DAC capability, or you need a DAC box between the media block and the amps.