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7
MAINTENANCE
PREVENTNE MAINTENANCE
The M5700 Program Amplifier is designed
for long, trouble-free service.
However,
as with all high quality electronic equip-
ment, a regular program of inspection should
be followed.
It is recommended that when the amplifier
is first placed in operation, D.C. voltage
be measured with the same voltmeter that
will be used for maintenance and trouble
shooting, and that these readings be record-
ed on the amplifier schematic above the
typical voltage shown"
Dust and dirt should be periodically remov-
ed with a soft brush.
SERVICING
When servicing the amplifier, the following
,:Joints should be observed:
I"
The condition of the output stages, 07
and 06, can be most readily checked by
measuring the D. C" voltages associated
with thes e stages.
2. Circuit resistances should be measured
only after removing the associated trans is -
tor or transistors, to prevent damage due to
ohm-meter battery voltage.
3"
Do not remove or insert transistors with
the power on.
4.
Do not probe the printed board with a
metal probe
with
the power on.
5. Circuit voltages are reversed from stand-
ard vacuum tube practice, as is the polarity
of all the electrolytic capacitors.
6.
The location of the positive end of each
electrolytic capacitor is indicated by the
white dot marked on the top of the circuit
board.
PRINTED CHASSIS COMPONENT REPLACEMENT
CHECKING COMPONENTS
I"
The components should
be carefully
checked by measuring circuit voltages and
resistances before attempting to remove one
of the leads from the printed chassis.
Ex-
treme care must be exercised in removing
the lead to prevent damage to the board or
conductors. This operation should not be
considered unles s
it
is the only way the
component can be checked"
If
one lead must
be removed without damage to the compo-
nent, apply a well cleaned and tinned 25 to
60 watt iron to the fillet adjacent to the
lead. With small long nose pliers or thin
,~
'crewdriver, pry the folded portion of the
~'iead
in line with thE! holes.
Applying the
iron for more than four seconds at a time
may damage the chassis base material.
Remove as much solder from the lead as
possible. Remove all the kinks in the wire.
With heat applied,
gently pull the wire
through the hole.
RESOLDERING THE COMPONENT
2.
If
the component is good, replace as
follows:
Use a metal twist drill (1/8" dia.
or less) to clear the hole only in the fillet
of solder.
Turn with the fingers only re-
move solder slowly to prevent the drill from
tear ing the fillet.
I
Fig. 7 - Cleaning Holes
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