Dolby IMS 3000 dimmer issue

[Mukesh Kumar]

Hi,
I am facing an issue with IMS 3000 dimmer. When the dimmer cable is connected to IMS 3000 GPO, the dimmer ON/OFF LED keeps glowing. I have tested it on another screen and the same issue occurs.

Troubleshooting done so far:

Checked ims with another dimmer → same issue.

Installed another IMS in the same screen → Dimmer is working properly.


From the above checks, it seems the issue is with the IMS 3000 itself.
Can you please confirm if the IMS is faulty or if there is any configuration that needs to be checked?

[Caleb Williams]

Hello there

Can you confirm what type of dimmer you're connecting to?

Please also post the contents of the macro you're using to trigger the GPIO/dimmer

When the dimmer on/off led is lit, does that prevent you from manually changing the dimmer?

Did you try swapping the GPIO cable before you swapped the IMS servers around?

[Shibu Paul]

“The IMS3000 automation must be connected with a dimmer interface. Could you please confirm which dimmer units are currently in use?”

[Dave Macaulay]

It does seem that the GPO on that server is faulty if another dimmer has issues with that one but is OK with another one. It may be working OK within its specs but the dimmer circuit needs some modification. I can't find an IMS3000 GPO circuit schematic but they often need a pull up or pull down resistor to ensure switching is positive.
Probably not useful information, but I avoid GPI/O when possible and prefer network interfaces like Jnior or EPRAD. A problem device may fry the server circuit, whether an opto isolator or open collector - on a pretty expensive board. A relay output is hard to damage and cheap to fix.

[Leo Enticknap]

My memory is a bit hazy, but IIRC, the GPIOs on an IMS3000 require an external 5-12V power source (e.g. by adding a wall wart to the circuit) and/or pull up resistor: they don't work as simple dry contact closure connections. In any case, using them is such a PITA that to operate relays using cues in an IMS3000 SPL, we've always used a separate device that can be triggered by commands over IP, e.g. an automation controller, JNIOR, or IP2CC.

[Steve Guttag]

The IMS3000 GPO is on open collector circuit:

image.png
It would appear that it is good up to 24V and needs a minimum of 5VDC pull-up.

The GPO connector does provide the +5V (and ground reference), if needed:

image.png

I'm in the camp of using a proper automation for the dimmer interface or some form of GPO to relay. You may find that the GPO is pulling down your device's input pin without a suitable pull-up.

[Mukesh Kumar]

20251012_014847.jpgcurrently using this dimmer.

[Mukesh Kumar]

When i connect dimmer with this IMS3000 control 1 and off led is glowing red and blue. Looks shorting dimmer.

[Shibu Paul]

Mr. Mukesh Kumar,
At least use Darbari brand dimmers and interfaces.

[Caleb Williams]

When i connect dimmer with this IMS3000 control 1 and off led is glowing red and blue. Looks shorting dimmer.

Does it remain shorted after removing the connection to the IMS? If it does, then you have a problem with the dimmer. If the short goes away, then there is a problem with the IMS server or the cable itself.

Based on information you've previously provided, it sounds like something in the IMS GPIO failed. If your comfortable modifying the automation commands and changing the wiring, you could try using different outputs on the GPIO.

[Leo Enticknap]

If the GPOs on the IMS3000 are borked and the IMS3000 is out of warranty (if it's still in warranty, then presumably the dealer you bought it from can set up a return/exchange repair), then another option would be an external relay interface, commanded over IP from the IMS3000. I use the IP2CC in situations like this, and have been very happy with it, but there are several other similar devices on the market. Not sure what is and isn't easily available in India, though.