ence voltage of 0.73V to the voltage across RT601. When placement Kit Number (RKC) or part number, description,
an unusually high temperature of 70°C (158OF) is reached product model number, and serial number.
on the heat sink, RT6Ol's voltage will have dropped to the
reference voltage and U503A or U503B will change state, FUSE REPLACEMENT
turning theTEMP on WARNING LED (D801). If the tempera- To replace line fuse F1, disconnect the line cord from
the ac source and remove the rear-panel fuseholder cap.
ture continues to rise to 100°C (212OF), RT6Ol's voltage
drops below 0.3V, U503C or U503D changes state, turning Replace the defective fuse as shown in the table. The fol-
off Q502 and Q501, opening relay K1, and turning on the lowing rear-panel symbols denote a fast-operating fuse
m~; and a slow-blow (time lag) fuse rT
SHUTDOWN LED (D802). In this condition, power the amps
are partially powered all other but (low-level) circuits and
the fan (BI) remain fully on. This condition remains until Model Operation at Fuse Type
the temperature on the heat sink drops to 70°C, when the
700 120Vac~10% IOA, 250V
LEDs turn off and full power is restored to the power amps. 3AB, ABC
RT501 is a positive-temperature-coeffic~ent thermistor 700 200,220,240 Vac* 5A, 250V 3AB, ABC
with a threshold at 120°C (248OF). It is mounted on the 700E6 100,120,140 Vac IOA, 250V 10A/250V
Power Supply board (A5) in front of 61 fan in the path of the (6.3 x 32 mm)
air flow through PC the board-fan assembly. When air 700E6 200,220,240 Vac 5A, 250V, T5/250V
motion is severely restricted, RT501 heats and its resist-
ance Increases (from 450 to approximately 1200 ohms). Time Lag (5 x 20 mm)
706 120 Vac " 10% 4A, 250V, AGC, 3AG
The current through R502 is reduced and the voltage SLO BLO
drop across R502 is not enough to keep transistor Q501
turned on. (2501 turns off, opening relay K1 and turning 706 200,220,240 Vac* 3A, 250V, AGC, 3AG
on the SHUTDOWN LED. It is extremely important that SLO BLO
RT501 should be mounted in the path of the air flow, its 706E6 100,120,140 Vac 5A, 250V 5A/250V
body perpendicular to the flow, approximately %" from (6.3 x 32 mm)
and not bent flat against the power supply board., 706E6 200,220,240 Vac 3.1 5A, 250V, T3.15/250V
The SPEAKER OUTPUTS dc sensor circuit is comprised Time Lag (5 x 20 mm)
of comparator U504 and associated components. A portion
of the output voltage is derived from the divider network of 'Rewired (see Operation at Other Voltages).
R640 and R641 on the power amp board. It is fed to the ,-CAUTION I
comparator inputs, and capacitors C509 and C510 remove
the audio signal leaving the only dc component. When the If trouble symptoms-overheating, erratic operation,
dc output at SPEAKER the OUTPUTS jacks exceeds + 3QV, etc.-were apparent before the fuse blew, or if the
replacement fuse blows, a qualified serviceman
U504 changes state, cutting off transistors Q501 and (2502, should troubleshoot the console carefully to find the
opening relay K1, and turning on SHUTDOWN LED D802.
Note that, when the comparator outputs change state, source of the trouble. Do not continue to replace
diode D509 and resistor R518 cause "latching"; the power fuses until the trouble corrected. is
switch must be turned off and back on to reactivate the I I
console. This feature is designed to call attention to the The Consoles also contain four fuses (F501-F504) on
presence of excessive dc at the output, which is an abnor-
mal condition and probably requires servicing. the Power Supply board (A5). If replacement becomes
necessary, replace only with identical fuses. Models 700
and 706 use type 3AG, IA, 250V, SLO BLO, with "pigtail"
leads. Models 700E6 and 706E6 use 5 mm x 20 mm, lA,
SERVICE INSTRUCTIONS 250V, Time Lag fuses.
EXTERNAL PARTS
The following parts can be removed and replaced with-
Voltages in this equipment are hazardous to life. out disassembling the console:
Refer servicing to qualified service personnel. Air Filter (MP1)
Knob, Rotary (MP2)
Knob, Slider (MP3)
REPLACEMENT PARTS Handle (MP4)
Parts that are readily available through local electronic Foot (MP5)
parts distributors are shown not on the accompanying Parts All knobs are pull-off and types are interchangeable.
List. Their values are shown on the Circuit Diagrams. Com-
mercial parts not readily available and unique parts are SERVICE ACCESS
shown on the Parts List and may be ordered directly from Disconnect the console from its ac power source. To
the factory. open the console for servicing, carefully place console the
The commercial alternates shown on the Parts List are on a firm, flat surface with the handle upward (sitting the on
not necessarily equivalents, but may be used in the event rear bumpers). Remove the air filter and remove nine
that direct factory replacements are not immediately avail- screws and eight washers securing the bottom panel to the
able. To maintain the highest possible performance and cover (four from the front and five from the rear of the
reliability Shure factory replacement parts should be used. bottom panel). Carefully rotate the console until the bottom
When ordering replacement parts, specify the Shure Re- panel rests on the work surface and extend either side |
ACEC
