Help! Clicking relays and flashing LEDs on power up!

[angelotaylor]

Hello!

I have a problem with my desk, and I need a help. Sometime, when I turn on the console, its LEDs flash and I hear the relay click. This may continue until the OS starts loading, or it may stop and the console will load normally. If the console doesn't load, its computer displays a DSP control card error. What could be the problem? I moved the thick power cable behind the console and the problem disappeared. Is contact broken somewhere?

[Crash]

Mine would do that from time to time... I would just shut it off and let it chill for a moment and try to boot it again. I never let it just put on the light show. If you can't get it to stop ever, then you may have a problem with rail caps. No fun there.

From the database:

Over the years, since the d8b's introduction, there have been many cases reported of the desk exhibiting what can only be described as lunatic behaviour. This behaviour has more often than not, been attributed to faulty or failed “rail capacitors”.

The symptoms can be all or one or any combination of the following:

All leds on the desk flashing of their own volition
V-pots swirling back and forth
Faders dancing to their own tune
Thumps of about 2 per second emanating from the speakers
All meters pulsing in sync with the thumps
A low constant hum emanating from the speakers
Flashing or intermittent fluoro display
Control from the console is usually lost, but the GUI seems to keep responding when poked at by a mouse or addressed with the keyboard.
A general description of what a rail capacitor is and does is in order.

In electronic terms "rail" typically refers to one of the power supply voltages as in "the +12V Rail" Assuming that, a "rail capacitor" would be a filter capacitor on the secondary side of the power supply. These are usually relatively large value electrolytic capacitors and will usually fail in the "open" state. The purpose of these caps is to filter out any AC component to the voltage on the DC bus (rail). If the cap opens then it is basically like it was not there and AC noise on the rail won't get filtered. Components like comparitors and A/D converters use the DC buses for reference and AC on the bus can potentially wreak havoc. The most common symptom of failed power supply filter caps is 60 cycle, or 120 cycle hum. (Courtesy: zandtanista)

The Famous d8b Rail Capacitors are indeed connected between the power supply rail and ground, but they're not the power supply filter capacitors, they're decoupling capacitors on the various boards, designed to keep hash generated on the board from getting off the board and on to another board through the power supply wiring. They're surface mount capacitors, 0.1 uF I think. (Courtesy: Mike Rivers)
The capacitors that fail have been traced to a faulty or wrongly marked batch (the voltage rating marked on the component was higher than its actual rating) and were installed mainly in the earlier boards. If you have what is called the newer motherboard in your CPU (find out here) and the desk is of the same era, you are much less prone to experiencing the problem.

Long story short, these “bad” capacitors can fail over time and you may experience the abovementioned symptoms.

The advice then, is:

If you find yourself in the rail capacitor boat, resign yourself to the fact that you will need to send the board back to The Mothership for service. Trying to trace and ascertain which cap is bad and then, even if you find it, attempting to de-solder the old and solder the new SMD, which will require the patience of Job, is going to cause you way more grief than putting your hand in your pocket. As a future proofing measure, since you've gone to the trouble of shipping your console and it's open and the soldering iron is hot, it's worth requesting that the service tech replace all of the bad decoupling caps. These things cost cents. The labour may increase the cost marginally but not as much as having to ship it again and again etc.

Get into the habit of either turning your monitors (Main, Nearfield and Headphone) down on the amps or preferably off when you leave the d8b on and unattended for any period of time. Many a set of monitors has been reduced to dust if a rail cap goes. You should, at least, avoid that extra expense.
The obligatory anomalies:

Sometimes clock failures exhibit some of the same symptoms as a blown rail capacitor.
Booting the board while digital inputs or clock inputs are active can also cause some of the same symptoms.
Short power interruptions can also exhibit some of the same symptoms.
Ask on the forum about your individual symptoms before sending the d8b off for service.