SERVICE MANUAL

AudioBox AB64

updated 21 June 2007

Analog Board Reliability Advisory

Contents

This manual provides troubleshooting and servicing information for the AudioBox model AB64.

Please read this short document carefully. It contains important information about possible sources of difficulty, tests that may be performed and corrective actions that may be taken.


What to Do First:

Please consult the AB64 User's Manual for setup information.When an AB64 that has been set up and working properly subsequently seems to be malfunctioning, do the following:

  1. Verify AC power connection to external power supply
  2. Verify connection from external power supply to AudioBox
  3. Verify power supply is generating the correct voltage (no less than 13.0 VDC and no more than 15.0 VDC)
  4. Verify audio connections and proper functioning of all connected audio equipment
  5. Verify ethernet cabling and connections
  6. Verify MIDI cabling and connections
  7. Try rebooting both the AudioBox and the control computer or interface


Startup / Firmware problems

If the AudioBox does not start up properly, the problem can often be resolved by reinstalling the latest firmware, clearing the default show on the drive, or clearing the file directories.

Reinstalling Firmware

The lastest firmware is always available on the download page on this web site. See the Richmond Sound Design web site to download the Windows installer and the download page on this web site for the Mac OS installer. Instructions for running the firmware installers are included in the downloads.

Booting to ROM

To install new firmware, it is sometimes necessary to prevent the firmware currently installed on the AB64 disk from running. This is done by powering on the AB64 and immediately pressing the leftmost pushbutton on the front panel. "BOOT TO ROM" will appear at the bottom of the LCD screen, and "RUNNING IN ROM" will appear at the end of the bootup period. At this point, firmware installation can proceed.

Default show problems

If there are still startup problems after reinstalling the firmware, it may be that the default show (the show file that is automatically opened wihen the unit starts up) is causing problems. Clearing the default show will prevent opening the default show file during startup which may allow the AB64 to start up normally. To clear the default show, power on the AB64 and immediately press the leftmost pushbutton on the front panel. "BOOT TO ROM" will appear at the bottom of the LCD screen, and "RUNNING IN ROM" will appear at the end of the bootup period. Go to the UNIT SETUP LCD page and perform the CLEAR DEFAULT SHOW command.

Clearing directories on the disk drive

If there are still startup problems after clearing the default show, there may be a corrupted file directory on the disk. Power on the AB64 and immediately press the leftmost pushbutton on the front panel. "BOOT TO ROM" will appear at the bottom of the LCD screen, and "RUNNING IN ROM" will appear at the end of the bootup period. Go to the UNIT SETUP LCD page and perform the the CLEAR DIRECTORIES command.


Internal Disk Drive

Drive does not spin up

Verify that the drives are installed correctly. See the Internal Disk Drive secton in the User's Manual.

Check power voltages to the disk drive. If the are bad, do not reconnect the power connector to the disk drive. Return the CPU board or the entire AB64 for servicing.

If the disk drive power voltages are normal and the drive does not spin up, the disk drive is defective, there is a problem with disk drive data cabling, or there is a problem on the AB64 CPU board.

Other Disk Drive Errors

Perform the procedure to clear drive and reinstall firmware, above.

Drive Defragmentation

A defragmentation of the internal AudioBox disk recovers unuseable disk space that accumulates as files are erased and re-written on the disk. The only legitimate reason to defragment a disk is to retrieve disk space when a disk is almost full and the recoverable disk space is needed. Defragmenting a disk will not repair a damaged disk directory or correct any other fault condition. Nor will defragmenting a disk make playback work better in any way.


Audio Artifacts

There have been occasional reports of audio artifacts in an AudioBox output variously described as clicks, thumps, buzzes, etc. The following is a checklist of possible causes:

  1. Ground loops can exist between the AudioBox and connected equipment. It is especially important that any connected computer be connected to the same AC power source as the AudioBox. If the equipment is in a rack, the rack must be grounded to the same electrical ground as all the equipment in the rack. Other equipment electrically connected to the AudioBox chassis must not inject noise into the ground system, especially if the AudioBox outputs are connected unbalanced. These recommendations hold true for audio equipment in general.
  2. Mixing single-ended outputs with balanced inputs is inadvisable. The reason this causes problems is that the ground coming from a balanced device can be, and often is, a dirty AC ground since it is basically a chassis ground (AC safety ground) that doesn't carry signal. The noise from this ground gets injected into the AudioBox ground system, which is OK as long as the entire system is balanced. But with, for example, an unbalanced output, the ground is being used as a signal ground, and SCSI signal currents can modulate the noise in the grounding system, causing a low-level buzz in the output that correlates with SCSI activity. If everything is unbalanced, no problems have been reported, because single-ended devices have to produce clean grounds. And if everything is connected balanced, which is the obvious recommendation, no SCSI noise has ever been reported in the audio outputs.
  3. Phantom power should never be applied to AudioBox inputs or outputs.
  4. Equalization and delay settings should only be changed on muted channels, as stated in the AudioBox command set and in the documentation for AudioBox control software. In particular, if clicks or thumps are heard at the start of a cue, the cue should be examined to see if it contains EQ or delay commands along with commands that open gain channels. If so, either split the cue or delay the gain commands that open the audio channel or channels by several frames. Digital equalization and delay algorithms can sometimes introduce audible noise (clicks and thumps) at the instant when the parameters to these functions are changed. It is, of course, possible to implement digital equalization and delay functions that are entirely free of these artifacts, but these implementations consume roughly twice the DSP horsepower as the functions that are implemented in the AudioBox. The AudioBox, like many other digital audio processing devices, was designed to deliver the maximum amount of signal processing possible with the available hardware resources, with the understanding that equalization and delay settings are to be kept static on live channels.
  5. Excessive levels can cause clipping, especially if equalization is in use that boosts a frequency band. The AudioBox gain matrix is, technically-speaking, an attenuation matrix, meaning that the gain functions always cut gain, never boost it, making it nearly impossible to cause internal clipping. Another way of saying this is that a fully open channel (input gain at max, crosspoint gain at max and output gain at max) is a unity gain channel from input to output. The audio inputs clip at +20 dBu. With EQ, however it is possible to add gain to selected frequency bands, which makes internal digital clipping possible. Care must be taken when EQ with gain is combined with high signal levels. Playback audio material from the internal disk drive is connected to the matrix input without attenuation. A gain-normalized audio file by definition has at least one full range sample in it; at this point in the file the signal is at an instantaneous level of +20 dBu. If any EQ with gain is added to a channel that has its input level full-on into which is playing back a gain-normalized audio file, clipping will occur.
  6. Distorted audio can find its way into the selections stored on the internal disk drive, either before or during the transfer of the data to the AudioBox. In this case, distortion will always occur in the same playback location (or locations) every time the selection is played back. It is possible to transfer the file back to the host computer, and check for any differences with the original sound file.


Hardware / Voltage Checks

Perform the following visual checks and voltage checks.

Visual Checks

Remove the top cover to the AudioBox and verify that all internal connectors are seated properly and that there is no obvious physical damage to the unit.Verify that there is no loose hardware.

Internal Power Checks

If the incoming power voltage is too high (over 15.0 volts), the "HI" LED on the back panel of the AB64 lights and the unit will not turn on. If the unit is on and the power voltage goes too high, the AB64 automatically turns off to protect internal circuitry. If the incoming power voltage is too low (below 13.0 volts), the "LOW" LED on the back panel of the AB64 lights. The unit may still operate with a low power voltage, but not reliably. When either the "LOW" or "HI" LEDs are lit, the problem with the external power voltage must be resolved before the unit is put back into service.

If the incoming power voltage is reversed in polarity or if the AudioBox is drawing too much power for some other reason, the power circuitry on the CPU board goes into a protection mode to prevent damage. In this mode, a polyfuse (a yellow device that looks something like a capacitor) near the power connector on the CPU board heats up, limiting the incoming current. When conditions return to normal, the polyfuse cools down and normal operation is reestablished, typically without requiring that the polyfuse be replaced.

If the incoming voltage is in range and the polarity is correct, a hot polyfuse indicates too much current is being drawn. Turn off the AudioBox, let the polyfuse cool, remove the power plug from the hard disk drive and restart the AudioBox. If the polyfuse remains cool, the disk drive is drawing too much current, and should be replaced. Otherwise, a main circuit board fault is indicated, and the unit should be returned for servicing.

The incoming power voltage can be measured on the CPU board at test point TP19 (this test point is after the polyfuse). See the voltage chart below.

CPU Board Voltage Checks

Touch the negative (black) lead of the voltmeter to ground (the chassis or a test point on the circuit board marked with a down arrow). Measure the voltages in the following chart with the positive (red) lead of the voltmeter:

Test Point

Nominal Voltage

Minimum Voltage

Maximum Voltage

TP19

14.0

13.0

15.0

TP18

3.3

3.1

3.5

TP20

5.0

4.75

5.25

TP23

12.0

11.0

13.0

Disk Drive Power Voltage Checks

Perform the CPU Board Voltage Checks (above) first. If the 5.0 volt and / or the 12.0 volt supplies are out of range, disconnect the power connector from the disk drive. (The power to the internal disk drive is supplied through a four-pin connector that plugs into the front of the disk drive next to the data cable.) Repeat the measurements at TP20 and TP23. If they are now within range, the disk drive is defective and should be replaced. If the voltages remain out of range, the CPU board or the entire AB64 should be returned for servicing.


Warranty / Service

Harmonic Functions Inc., Burnaby, British Columbia, Canada, warrants to the original purchaser that the AudioBox model AB64 (the product), excluding the internal disk drive (which is warranted separately by its manufacturer), and excluding the external power supply will be free from defects in materials and workmanship for a period of five years from the date of original purchase. Harmonic Functions warrants to the original purchaser that the external power supply will be free from defects in materials and workmanship for a period of 90 days from the date of original purchase. Harmonic Functions agrees, as its sole responsibility under this limited warranty, at its sole option, either to repair, replace, or refund the purchase price of any product discovered to be defective within the warranty period, upon receipt by Harmonic Functions. Any such replacement product may be, at the sole option of Harmonic Functions, a new product or a remanufactured product.

This limited warranty is not applicable to normal wear and tear, abuse, unreasonable use, mistreatment, neglect, damage caused by the equipment or system with which the product is used, or damage caused by modification or repair not carried out by Harmonic Functions.

This warranty and the remedies set forth herein are exclusive and in lieu of all other express or implied warranties (including any implies warranties of merchantability or fitness for a particular purpose) which are disclaimed and no other representations or claims of any nature shall be binding or oblige Harmonic Functions. In no event will Harmonic Functions be liable for any special, incidental, or consequential damages, including, but not limited to, damages resulting from use or malfunction of this product or the equipment or system with which it is used, loss of profits or revenue, or cost of replacement goods.

If you suspect a malfunction in an AudioBox AB64, contact your AudioBox dealer for further instructions.


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