CP650 Issue

[Steve Guttag]

You, obviously, didn't watch enough then. He is sharper than most people working a bench, past and present. It isn't that he complains about the cost of ESRs, he is just noting how expensive they can be and that he has an alternative that can indeed test power amplifier capacitors too. Again, if you came away with that impression, it is you who doesn't understand. You can watch other videos he has done to get a better sense of his knowledge/capabilities. Or, you can just think you figure out a guy in a few minutes...whatever. He has also revved is leakage tester so it has a couple more ranges now but still the same base design.

[Neal Scanlan]

Hello

I changed the capacitors and there was a small benefit in the time it takes for the unit to fail. It still requires a full power down/power up to reboot.
All of the voltages on the front panel are reading low by comparison to the quoted voltages in the installation manual. There is momentary drop in voltage that I just catch on the volt meter before the unit fails.

Top 3: In Bypass
-15v = 13.68v
+15v = 14.1v
-14vb =12.65v. 11.6v

Bottom 3:
+5v = 4.5v
+5vb = 4.6v. 4.6v
+14vb = 13.3v 11.8v

Do these figure throw light on to the problem for anyone?

[Neal Scanlan]

Looking at the power supply the are two trim pots V1 & V2. Would these be to increase/decrease voltage to the main boards, if so could anyone advise as to how to proceed assuming this is a potential help in sorting the issue with the unit?

[Mark Gulbrandsen]

Looking at the power supply the are two trim pots V1 & V2. Would these be to increase/decrease voltage to the main boards, if so could anyone advise as to how to proceed assuming this is a potential help in sorting the issue with the unit?

Never had top adjust the trimpots... they come factory preset. Assuming that replacing the capacitors fixes it, they should not need adjustment. Your voltages do seem a little low though. It could mean other issues with the power supply, or internal issues. Also check the contacts in the push on connectors for darkening.

[Mark Gulbrandsen]

You, obviously, didn't watch enough then. He is sharper than most people working a bench, past and present. It isn't that he complains about the cost of ESRs, he is just noting how expensive they can be and that he has an alternative that can indeed test power amplifier capacitors too. Again, if you came away with that impression, it is you who doesn't understand. You can watch other videos he has done to get a better sense of his knowledge/capabilities. Or, you can just think you figure out a guy in a few minutes...whatever. He has also revved is leakage tester so it has a couple more ranges now but still the same base design.

Watched four of his videos. I am impressed by his vintage test gear collection. I also own a number of the same pieces he has.

[Marco Giustini]

I think that one of those trimpots adjust the 5V, the other the 15V and the -15V - it won't be necessarily perfect but I would adjust it so it falls in the middle - such as +15.3V and -14.7V if that makes sense.

Before giving up on that PSU I would try adjusting them - disclaimer: you do that at your own risk

[Jim Cassedy]

650'a have become so (relatively) cheap right now, that I just keep a spare one around for either parts or emergency swapping.

[Neal Scanlan]

Hello,
So my conclusion is that the problem is with the PSU. I tested the voltages with the PSU out of the chassis and they were as per the previous tests taken from the points on the front of the 650.
I was able to increase the voltages by turning the pots but only by 0.5v still under the recommended voltages for the unit. On start up the voyage for the +15v was now 14.5v and the -14v was at -13v.

Over a period of about 30 minutes both these voltages slowly dropped in parallel until the unit defaulted to Bypass. This happened consistently over 5 x tests.

Does anyone agree that my test are indicating a problem with the PSU?

I can get a new PSU and will be on the look out for another 650 processor.

[Marco Giustini]

Yes, it seems to be the PSU indeed. Schematics are not available for that model but it sounds like an issue with the feedback - the PSU senses the outputs and adjusts the "switching" to keep it stable. Something is warming up and failing.

One thing you can try is "cold spray". It's a can of non-inflammable spray which freezes components. Once the voltages have dropped, you can start spraying areas and see if/when the PSU regains functionality. Then you can try single components in that area. Focus on the feedback area and the optocouplers, it's the area nearby the adjustment trimmers and towards the optocouplers - the black thingies which are across a gap on the PCB.

Sometimes it works, sometimes it doesn't. On a CP650's PSU I was able to pin-point a faulty tantalum capacitors but I had to freeze it to death - that is, it would not change its behaviour with just a quick spray.

The above if you want to play with it, best solution is to find another one of course.

And remember there are lethal voltages in a SMPS so you do that at your own risk.

[Tony Bandiera Jr]

Hello,
So my conclusion is that the problem is with the PSU. I tested the voltages with the PSU out of the chassis and they were as per the previous tests taken from the points on the front of the 650.
I was able to increase the voltages by turning the pots but only by 0.5v still under the recommended voltages for the unit. On start up the voyage for the +15v was now 14.5v and the -14v was at -13v.

Over a period of about 30 minutes both these voltages slowly dropped in parallel until the unit defaulted to Bypass. This happened consistently over 5 x tests.

Does anyone agree that my test are indicating a problem with the PSU?

I can get a new PSU and will be on the look out for another 650 processor.

Very high probability that is is a bad PSU, BUT there could also be a problem with something in the CP itself that is drawing excessive current as it heats up and is causing the issue.

One way to try to confirm it is the psu is to operate it with no load (not connected to the processor) and see if the voltage still drops over time. (That is if the psu doesn't have some sort of standby input that has to get feedback from the CP.)

If replacing the psu solves it with a test of 2 or more hours passing, then most likely nothing else is wrong. If however a replacement PSU gives the same results then best to replace the whole processor. (Or spend some time digging deeper into the unit.)

[Marcel Birgelen]

Depending on what budgets you're operating and how critical this piece of equipment is in your setup, I think the most economical way to go at this time is to look for a spare PSU and maybe even a spare CP650, like Jim indicated, they're pretty cheap nowadays. As soon as this fixes your original problem, you can still divulge your spare time into trying to fix your original CP650. A year or so ago, I fixed a CP750 with a similar problem by replacing a bunch of wonky caps on the motherboard itself. Like Tony indicated, the fault could also be in the unit itself, drawing too much current. Once a cap starts to leak, it's starting to operate more like a resistor than a capacitor, so leaky caps may cause your circuit to draw more current, which in turn, may cause a voltage drop across the main bus.

[Mark Gulbrandsen]

Like I said... Replacement of caps at 10 year intervals will prevent almost all down time with cinema processors. Steve claims his customers aren't interested in PM, but when they have to pay for an emergency call, 500+ miles of mileage, and over night shipping on a new PSU or mommie board, then they may feel differently about pulling normal maintenance. I always put it that way to my customers and they never said no to replacing caps on my next normal service trip. A technician also has to be a common sense salesman too.

[Steve Guttag]

It depends on the PM call. For mechanicals, I don't get too much fuss. For electronics? There are so many CPxxx that go closer to 20-years without incident, it is a tougher sell. I'm not saying you are wrong to recommend replacing a part that is known to age. For instance, on our UPSes, we try to get batteries replaced in the 3-5 year window...which should probably be narrowed to 3-4 years, I'm finding.

There does come a point where changing capacitors every 10-years, on working equipment, could mean they are spending money they could have used for newer, more current technology to replace obsolete equipment. So, really, you are more ensuring that, baring a freak failure, the cinema processor gets 20-years, which is likely enough to put it in the "unsupported" and notably obsolete category.

[Mark Gulbrandsen]

It depends on the PM call. For mechanicals, I don't get too much fuss. For electronics? There are so many CPxxx that go closer to 20-years without incident, it is a tougher sell. I'm not saying you are wrong to recommend replacing a part that is known to age. For instance, on our UPSes, we try to get batteries replaced in the 3-5 year window...which should probably be narrowed to 3-4 years, I'm finding.

There does come a point where changing capacitors every 10-years, on working equipment, could mean they are spending money they could have used for newer, more current technology to replace obsolete equipment. So, really, you are more ensuring that, baring a freak failure, the cinema processor gets 20-years, which is likely enough to put it in the "unsupported" and notably obsolete category.

Again, That's the job of the technician to determine weather to keep the old or buy the new.... Since many knew Digital Cinema was coming they chose to overhaul supplies at least back in the day..

[Leo Enticknap]

There does come a point where changing capacitors every 10-years, on working equipment, could mean they are spending money they could have used for newer, more current technology to replace obsolete equipment.

The problem in this case is that there is no easy replacement for a CP650, if its 35mm audio capabilities are needed. An AP25 with the optical preamp card is the only off-the-shelf solution I can think of, but then you'd lose SR-D (unless you added a DA-20 and automated the dropout to SR via GPIO, which is a significant science project, the end result of which will be that you'll still have some 15-20 year old equipment in use). Pretty much every used CP650 we acquire is resold almost instantly, either to replace one at an arthouse or other 35mm venue that is giving trouble, or because the owner wants a spare to hedge against the one in service starting to give trouble.