Turn off digital

[Tony Bandiera Jr]

I put switches on the BACP readers at UC Irvine https://www.film-tech.com/warehouse/...911&category=1 as we kept the processor and other equipment powered 24/7. It was very easy and Sam confirmed with me that I didn't void any warranty doing it.

I'd place the switch on the DC line from the processor that powers the entire penthouse, not right on the LED.

Oh, Mark, you little scamp. Why waste time and energy doing that? You'd have to use a double pole switch to break the + 15 volts, you'd then be slamming power off and on to the CCD as well (which BTW electrically is exactly the same as hot plugging the cable, a huge no-no), and just where would you break the connections to do all of that? KISS, Keep It Simple Stupid. Just break one side of the LED itself and be done with it.

Josh, Steve and Frank nailed it. TJ's solution is a bit overboard as now you have a relay(s) that could potentially fail and kill your sound.

Simpler is ALWAYS better when it comes to mission critical things like power for sound and projection, etc. Just look at the plethora of issues that digital projection brought to what was once a simple, mainly mechanical process.... light up a screen with moving pictures.

[Tj Hopland]

I wasn't the relay person, wasn't that the concept with the status led? I was just asking with side of the led driver board you would want to switch or if it doesn't make any difference? Short term either should work I was thinking before the board so you would maybe have a little more voltage and current to keep the switch contacts clean.

[Ryan Gallagher]

I wasn't the relay person, wasn't that the concept with the status led? I was just asking with side of the led driver board you would want to switch or if it doesn't make any difference? Short term either should work I was thinking before the board so you would maybe have a little more voltage and current to keep the switch contacts clean.

I think the person who mentioned relays was Josh discussing older penthouses with separate power (on switched outlets for automation purposes). I was not considering one in combo with the addon of an LED button.

Why waste time and energy doing that? You'd have to use a double pole switch to break the + 15 volts, you'd then be slamming power off and on to the CCD as well (which BTW electrically is exactly the same as hot plugging the cable, a huge no-no), and just where would you break the connections to do all of that? KISS, Keep It Simple Stupid. Just break one side of the LED itself and be done with it.

Josh, Steve and Frank nailed it. TJ's solution is a bit overboard as now you have a relay(s) that could potentially fail and kill your sound.

Simpler is ALWAYS better when it comes to mission critical things like power for sound and projection, etc.

Tony's points are also extremely fair, and does suggest that breaking power with a switch ahead of the DCtoDC board (on 702s) would be functionally equivalent to hot-plugging the reader, which has certainly been stated as something to avoid in other topics! So that is a no-go approach for me.

If one was seriously needing a status indicator it would probably be best implemented sharing the +15v main supply for the status LED circuit in the case of the 701/702s, and not actually needing one it feels like overkill... best to do what Steve, Frank, and everyone else has done and just plain vanilla switch for the reader diode line itself with no fancy status other than the reader's diode illuminating.

Mark was the one that suggested placing the switch ahead of the DC diode driver board. I think the main motivation for wanting this approach is it does not have any potential to affect the resistance (voltage drop) of the reader diode circuit, potentially shortening the tunable/usable lifespan of the diode itself. But if hot plugging/powering the CCD is really a no-no then this approach is potentially invalid. I suppose depending on the reader, if there is a separate diode driver board this is doable, but if on a shared DCtoDC board like the 702s then it is not. (at least not easily without board level mods).

Oh and Tony's point about the style of switch needing a double-pole if breaking the input +/- 15v input is also valid. The switch I linked previously would NOT do that business, even if it was advisable to take that approach.

[Paul Finn]

A simple no-fuss resolution to this issue is to just disconnect the reader cable connectors on the back of the processor with it OFF and DD is not needed/used.

Paul Finn

[Steve Guttag]

That works until someone forgets the "Off part" and zaps the CCD. Furthermore, Dsubs are not meant for a lot of uses.

[Ryan Gallagher]

That works until someone forgets the "Off part" and zaps the CCD. Furthermore, Dsubs are not meant for a lot of uses.

I also think the 702s just have a panel gasket and all the connections are inside (not in front of mine). Oh I see Paul meant on the processor. Yeah not providing instructions to our other ops to do anything in the back of the racks!

The whole point is to have them off when in Optical modes, but 650 is still needed, seems to leave too much room for an oopsie. With a diode switch the 650 can go back to just saying powered on like it used to.

[Tj Hopland]

This is a fun thread, we should see how complex we could make this. How about some sort mechanical governor tied to the sprocket that activates a switch? If its not a DD print you don't go around the sprocket so LED won't come on? Could go old school with brushes and mercury switches. Could go new school with a shaft encoder or maybe some sort of prox sensor to read the movement and solid state controls for the led. If you still have fire shutters in your projector you could run a piece of fishing line from the fire shutter up around a pulley that would then pull on Steve's patented switch design (or is it just the label?). Steve's switch and label is manual so if you had yours linked to the fire shutter you don't need the label and its not manual so no pesky licence fees involved?

I believe the hot plugging risk is all related to the main/camera board. I assume its not directly related to the power going on and off. I'm guessing the possible damage comes from things like which order various pins get connected and or that it may not be a smooth one time action. It could be something like +15 and and one of the hot video lines get connected before any of the returns make contact then you rock the connector slightly and the video pin makes and breaks several times If it was something designed to be hot plugged they would have used some sort of connector that had different length pins like maybe all the grounds and returns would be longer than the power and signal ones so you could then be reasonably sure those would make contact first. Think like most line/mains power plugs, the ground pin is longer so it makes contact first.

Did Steve say where in the path he put his switch(s) and I missed it?

[Frank Raia]

Well Tj, I have another alternative. I could buy another CP500 or a DA20 and hook only the Digital reader to the second one. This way All you have to do is turn the secondary unit off just like turning off the DTS system. How would that work with the original CP500 switching to optical if digital drops out? Another way I was thinking... Have all 4 (optical, SRD, DTS and SSDDS) hooked up to automation on a timer to cycle the power on and off to each in sequence order so they each get equal time during the same showing. Oh and the automation would some how have to mute the sound at each power on/off so the speakers would not blow.
This I believe would solve the hot swap problem.

[Jim Cassedy]

A simple no-fuss resolution to this issue is to just disconnect the reader cable
connectors on the back of the processor with it OFF and DD is not needed/used.

That's what I do at my venue when we are going into an extended 70mm engagement.
The risk of damage by hot-plugging/un-plugging here are very low, since I'm the only
permanent projection-tech on staff, and, if I get hit by a bus or am out sick or something,
the person they would bring in to fill in for me is equally experienced.

Our main audio processor here is a Trinnov Ovation, so our CP-650, and thus the
Dolby Digital readers are only powered up when running 35 or 70mm.
We've got a couple of KELMAR power supplies that power the optical sound
readers. The optical sound LED's only come on when the projector motor switch
on each projector is turned on. The Kelmar power supplies don't have a power
switch on them, but, I'll reach up into the rack and unplug the AC power to them
if we are doing an extended 70mm engagement.
( ie: LICORICE PIZZA, OPPENHEIMER, DUNE II, BRUTALIST, etc. )
> I also don't power up the 35/70mm magnetic sound pre-amps unless we're
running a print with mag-tracks. (yes, sometimes we still do that here!)

[Ryan Gallagher]

That's what I do at my venue when we are going into an extended 70mm engagement.
The risk of damage by hot-plugging/un-plugging here are very low, since I'm the only
permanent projection-tech on staff, and, if I get hit by a bus or am out sick or something,
the person they would bring in to fill in for me is equally experienced.

Our main audio processor here is a Trinnov Ovation, so our CP-650, and thus the
Dolby Digital readers are only powered up when running 35 or 70mm.
We've got a couple of KELMAR power supplies that power the optical sound
readers. The optical sound LED's only come on when the projector motor switch
on each projector is turned on. The Kelmar power supplies don't have a power
switch on them, but, I'll reach up into the rack and unplug the AC power to them
if we are doing an extended 70mm engagement.
( ie: LICORICE PIZZA, OPPENHEIMER, DUNE II, BRUTALIST, etc. )
> I also don't power up the 35/70mm magnetic sound pre-amps unless we're
running a print with mag-tracks. (yes, sometimes we still do that here!)

Similar here minus the single operator experience level. We are in a mode where we are actually trying to "grow" the number of capable projectionists in town, even if it means just other production department staff filling in due to an emergency. But in reality so far it's always been with one of the two staff projectionists shadowing the new to our booth recruits.

Outside local projectionists do operate, we have two on our rolodex, they are still learning the quirks of our booth and they have always had a shadow so far since we crew 2 to split the DCI Preroll & Backup vs Analog responsibilities. We also find we prefer the buddy system for catching any issues before they happen, worst case the 2nd person is VERY handy for being the FOH communicator in the event of a film stoppage for some reason.

This venue used to leave it's 650 powered on all the time (and thus the 702 diodes), had to replace them after the pandemic when I started. I switched them to putting it in standby when not in film mode.

To complicate the issue, prior procedures relied on the non-sync from the 650 for walkin music and intro mic, for ALL FILM (even DCI). About a year in I wired up an alternative non-sync path from the same mixer directly to the AP20. Both options exist but the norm now is to not boot the 650 for DCI engagements.

I think the main "logic" for leaving the 650 on was that it too is known to dislike constant standby cycling... I've seen mention of the standby button itself being the weak point. If we don't got back to always on due to adding a diode switch, perhaps I can double check that we can just turn the Furman strip rack power off in that rack instead... the 650 after all has zero standby functions it is required for, but preserving that physical button would be nice.

TJ, I'll have to think about my most Rube-Goldberg version of a diode enable... LOL. You could nest a Arduino powered non-contact tachometer inside a 702 reader, it would be aimed at the flywheel with a fleck of white paint on it's shaft or wheel. The arduino would switch the digital diode reader on if it detected an RPM at all. Now you've got tons of electronics and programming and maybe a relay that can fail. ;-) (Although a normally closed relay could mitigate most of the failure modes). This isn't all that different from what the Sony readers do, diodes only light when things are moving through the reader... but i'm sure their implementation is a bit more fool-proof.

[Jim Cassedy]

I think the main "logic" for leaving the 650 on was that it too is known to dislike
constant standby cycling
... I've seen mention of the standby button itself being the weak point. .

I have had to replace the push-button switches on two 650's that failed. (The buttons
failed- not the 650's!) - Fortunately both of them failed in the "ON" mode, so until I was
able to replace them, I would just reach behind the rack and pull the power cord out of
the back of the unit. The switches are fairly easy to replace, but both times I had to do
that, I decided to completely pull all the cards out and give the case, and the individual
circuit boards, a good cleaning with a soft paint-brush and compressed air to get rid
of all the 'booth dust-bunnies' that accumulate on equipment after a while.