Adcom MOSFET GFA-5802 - Manual (Page 7)

FRONT PANEL FEATURES
POWER LED
This LED will glow whenever the AC ON/OFF switch is turned on and the GFA-5802 is energized. The POWER LED
indicates that there is AC voltage being fed to the amplifier, but it does not signify that all the amplifier’s circuits are in operation.
If, for example, the THERMAL PROTECTION LED glows, the amplifier will not produce sound even though the POWER LED
may still glow. Additionally, the internal power transformer is provided with a thermostat which will interrupt power to the
transformer if its temperature exceeds 125®C. This high temperature will seldom, if ever, be encountered unless the amplifier is
subjected to abnormal conditions, such as operation into loads of less than 2 ohms at very high listening levels for long periods
of time, etc Once the temperature within the transformer decreases to a normal level, the thermostat will reset itself
automatically and normal operation will resume
INSTANTANEOUS DISTORTION ALERT LED’s
The INSTANTANEOUS DISTORTION ALERT circuit is a unique ADCOM distortion detection system which reads all
forms of non-linear distortion such as THD, IM, slew-induced, “clipping”, etc. The INSTANTANEOUS DISTORTION ALERT
LED’s will light when distortion reaches 1% regardless of impedance, voltage/current phase angle or the reactance of the
loudspeakers which the amplifier is driving. Sometimes, when the amplifier is in use, the LED’s may occasionally flicker during
high volume listening, particularly if you are driving low impedances This flickering is no cause for concern The LED’s are
simply warning you that the amplifier has reached its maximum power output into the particular loudspeakers you are using. If,
however, the INSTANTANEOUS DISTORTION ALERT LED’s glow brightly or are illuminated most of the time during playback,
you are overdriving the amplifier and should turn down your volume control to reduce the listening level, otherwise it may cause
the THERMAL PROTECTION to be activated or, in extreme cases, damage your loudspeakers
THERMAL PROTECTION LED’s
The GFA-5802 is provided with a thermal protection circuit which will shut down the amplifier if either heatsink’s
temperature reaches 85®C The THERMAL PROTECTION LED’s will light whenever the thermal protection circuit on its
respective channel has been triggered and the amplifier is inoperative The thermal protection circuitry will typically be triggered
by very high power demands into impedances much lower than the amplifier is capable of driving at those levels. If either
amplifier channel's output through the loudspeaker(s) ceases abruptly, and one or both of the THERMAL PROTECTION LED’s
glow, you will know that the circuitry is protecting the amplification devices. Once the temperature of the heatsink(s) drops to a
safe operating level, the amplifier will automatically resume operation.
Activation of the thermal protection circuitry in the GFA-5802 is an indication that the amplifier has been overdriven or
that the load the loudspeakers are presenting to the amplifier is unreasonably low. If you wish to prevent recurring activation of
the thermal protection circuitry, you must reduce the volume level demands or correct the load-impedance condition which may
be causing activation of this circuitry, or both internal protection fuses may blow.
Another reason that the THERMAL PROTECTION LEDs will glow is if the Speaker Outputs (O or O) are shorted (if the
positive and negative wires were to touch together). If this occurs, you will experience severe distortion from the speakers for a
few seconds. The amplifier will then shut down and the PROTECTION LEDs will glow.
SERVICING
ADCOM has a Technical Service Department to answer questions pertinent to the installation and operation of your
unit. In the event of difficulty, please contact us for prompt advice. If your problem cannot be resolved through our combined
efforts, we may refer you to an authorized repair agency, or authorize return of the unit to our factory
Please address mail inquires to.
ADCOM Service Corporation
11 Eikins Road
East Brunswick, NJ 08816 USA
Phone or fax inquires to'
Telephone: (908) 390-1130 or after 7/97 (732)
Fax: (908) 390-9152 or after 7/97 (732)
Monday through Friday
9:00 AM to 5:00 PM EST
When calling or writing about your GFA-5802, be sure to note and reter to its serial number as well as the date of
purchase and the dealer from whom it was purchased. In the event the unit must be returned to our factory for service, you will
be instructed on the proper procedure when you call or write for a Return Authorization UNDER NO CIRCUMSTANCES
SHOULD YOUR UNIT BE SHIPPED TO OUR FACTORY WITHOUT PRIOR AUTHORIZATION.
If the original shipping carton and its fillers have been lost, discarded, or damaged, a duplicate carton may be obtained
from our Service Department for a nominal charge
Always ship PREPAID VIA UNITED PARCEL SERVICE (UPS) OR OTHER APPROVED CARRIER. DO NOT SHIP
VIA PARCEL POST, since the packing was not designed to withstand rough Parcel Post handling FREIGHT COLLECT
SHIPMENTS CAN NOT BE ACCEPTED UNDER ANY CIRCUMSTANCES.