RT-14 12V Chip Blown — Trigger Box Loses All LEDs and Functionality¶
Summary¶
The MRMC DB37 Trigger Box loses all functionality — no LEDs light up, no relay outputs fire — despite appearing correctly connected and configured in Flair. The fault is internal to the RT-14: a 12V power chip on the RT-14 board has blown. The Trigger Box itself is fine; it is simply receiving no power from the RT-14. Diagnosis is with a multimeter; fix requires RT-14 service/replacement.
Symptoms¶
- All LEDs on the Trigger Box are dark — including status LEDs that should always be on
- No trigger outputs fire during test or during runs
- Flair reports no errors related to triggers
- The Trigger Box works correctly when connected to a different RT-14
- Problem appeared suddenly, not gradually
The RT-14 12V Power Supply to Trigger Box¶
The RT-14 provides 12V power to the connected Trigger Box via the DB37 ribbon cable connector. This 12V is generated by a dedicated chip on the RT-14 PCB. The Trigger Box's relay outputs run from this 12V supply.
If this chip fails, the Trigger Box receives no power and appears completely dead.
This chip is not fuse-protected
Simon Wakley confirmed: "It's not hard to blow up." The 12V chip has no fuse protection. Excessive current draw (from connected trigger loads, short circuits, or inrush from capacitive loads) can destroy the chip without warning.
Diagnosis¶
Step 1 — Confirm It's the RT-14, Not the Trigger Box¶
Connect the Trigger Box to a different RT-14. If LEDs come on and triggers fire normally, the Trigger Box is fine — the fault is in the original RT-14.
Step 2 — Measure 12V at the DB37 Connector¶
Using a multimeter, measure the voltage between the 12V pin and the GND pin on the DB37 ribbon cable connector (at the RT-14 output, with the Trigger Box disconnected or with a breakout/probe adapter):
| Measurement | Interpretation |
|---|---|
| ~12V | 12V chip is functioning — fault is elsewhere |
| 0V | 12V chip is blown — RT-14 needs service |
Refer to MRMC wiring documentation for the exact pin numbers for 12V and GND on the DB37 connector.
Test with Trigger Box disconnected if possible
If the chip blew due to an overcurrent condition, leaving the Trigger Box connected during diagnosis could further stress the circuit. Disconnect the load and measure the open-circuit 12V to confirm chip function.
Fix¶
The 12V chip is a surface-mount component on the RT-14 PCB. Replacement requires component-level soldering skill and access to the correct replacement part.
Options: 1. Send to MRMC for service — recommended; MRMC can repair or replace the RT-14 2. Component-level repair — if you have an electronics technician available; identify the blown chip from the MRMC schematic 3. Swap RT-14 — if a spare RT-14 is available on set, swap immediately and arrange service for the blown unit
Prevention¶
The 12V chip is susceptible to overcurrent from connected trigger loads. To reduce risk:
- Do not connect high-current inductive loads (motors, large solenoids) directly to the Trigger Box relay outputs without protection
- For high-current trigger loads (e.g. large bloop lights, solenoids), use the Trigger Box relay as a low-current switching signal to control an external relay or SSR rated for the actual load
- Avoid short circuits on trigger wiring — always test new wiring before connecting to the RT-14
Community feature request
Multiple operators have requested that MRMC add a replaceable fuse to protect the 12V chip in future RT-14 revisions.
References¶
- Duncan Weinland, Simon Wakley, Gordon Eschke — November 2024
- MRMC RT-14 Quick Start Guide
- TRIG-ethernet-trigger-box-cinebot-ric-ini — different trigger box type (Ethernet, Cinebot Mini)
Official Documentation¶
WhatsApp Excerpts¶
- 2024-11-22 07:21 - ~ Simon Wakley: I would check the connector that says 12v to Gnd and see if maybe you’ve lost your 12v. It is a separate chip in the rt14 and can be blown. You have a meter?
- 2024-11-22 07:23 - ~ Duncan Weinland: Am I checking the 12v pin and GND pin on the Trigger box when all hooked up?
- 2024-11-22 15:31 - ~ Simon Wakley: That Chip on the RT14 is not hard to blow up. MRMC should possibly add a fuse? Any idea what might have blown it. You do have to be careful with the 12v as it does only supply limited current.
- 2024-11-22 15:41 - ~ Steven Carlson: Is there a published spec for what that current limit is?
- 2024-11-22 16:48 - ~ Peter Constan-Tatos: Agree. Fuse should be on the triggers box for easy access as this is where any fault is created.