The Dimmer Doctor's Page of Troubleshooting Hints

Troubleshooting is art and science combined with plenty of common sense and it can be Dangerous. Depending on your technical and common sense strengths your approach may vary. One thing to keep in mind is that the equipment was working properly and now isn't so something has failed.

The answer depends on collecting information and answers to what the Dimmerdoc believes are "simple" questions.

The "Simple" Questions:

How is it supposed to work?

What is it doing now? (How is it not working?)

What happened just before it stopped working properly?

Have you personally witnessed this problem or is it being reported? Do not discount "operator error" that can occur under the stress of production demands.

Is it a continuous ("bad" all the time) or intermittent problem?

Intermittent problem:

Mechanical Intermittence: Can you make it happen by wiggling or banging something or does it take some time for the problem to occur? Intermittent problems that you can cause by mechanical means can usually be tracked down quickly.

Or

Time Related Intermittence: Does the intermittance occur and become continuous after the system has been on for a while (how long is "a while")? This often means a heat related problem. If it is within the dimmer (swap out the "bad" dimmer for a known good one to be sure), the dimmer will have to be repaired. If the dimmer is "good" then using a signal tester, logic probe, and/or oscilloscope and schematics may be the only recourse.

Continuous problem:

If practicable, try swapping dimmers to make sure the problem follows the dimmer.

Is the dimmer failed-on (load is full bright with no control signal and can only be turned on/off with circuit breaker)? This usually means a shorted dimmer that must be removed and repaired.

Is dimmer failed-off (load stays off no matter what is done to the dimmer)? This usually means either a no power or no signal condition.

Is the dimmer either partially on and will dim up to full, or will it dim from off to partially on? This often means a failure in one of the SCRs that will require dimmer removal and repair. The other cause is misadjustment of front panel controls on the individual dimmer. (Older "analog" dimmers usually have these controls. Newer "digital" dimmers do not.)

No Power Condition:

The following tests may expose you to lethally dangerous voltages. Do not attempt them if you are the least bit unsure of what you are doing. Call in an experienced electrician not an undertaker.

Is power connected?

Are fuses OK and circuit breakers on?

Is a load connected? [Test load in a "hot" or test outlet (without a dimmer) to prevent damaging another dimmer if load is shorted.]

Does the dimmer or dimmer controller (at the dimmer) have a self-test switch, control, and/or light? If your dimmers have this feature you can make sure the problem is dimmer related before chasing down a control signal problem.

No Signal:

Is a control cable connected? (Check both ends of control cable and connectors for bent/broken pins.)

Is control console on and working properly? (If there is more than one control cable try swapping cables at the console to see if problem follows cable or stays on same dimmer.)

If signal is AMX, DMX or other "multiplexed" "digital" signal, is the signal OK? (You may have to get a tester for this unless you have a test switch and/or light on the dimmer end of the cable or know how to use a logic probe or oscilloscope.) In this case the easiest test is to swap out the cable, then the console, and finally the decoder at the dimmers.