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J FT. D100
° ; CHECKING THE OPERATION OF THE PRO TECTION CIRCUIT
AC voltmeter
"Oscilloscope =
Wechselstrom
. ———sOsszillograph
|
OUTPUT ©
Audio oscillator
: Frequenzgenerator .
a
Oscillateu d 'onde sonore
output transistors, etc., perform an operation check on
—-- cuit >
bee
the ASO (Area of Safe Operation) detection circuit forthe
| Make sure 'that ihe: on operates (a click sound | is
: output transistors and 'the: aeoued poe) a
heard) approx. 7-10 seconds after the power switch
—
~. is turned on with the poe aners terminals unloaded
1. Operation check of the ASO. detection cireuit _ _ (speaker: disconnect). -
ee ae
forthe
=> ee
nae
Next, when a resistor with a resistance of See
eee
Conne:
2 oscillator to the TUNER IN ter
"40 k ohms and two. 1.5: dry batteries are connected in.
minals ..
—aker terminals unloaded (speaker:
series across. pins 5 and 2 of main power printed wiring
disconnect). Se —— frequency of the audio oscillator. _
board 1C901, the relay turns off within 1 sec. Next,
at 1 kHz and adjust the level of the input signal so —
-- when. power is turned on again after at least 10 seconds
that the voltage at the speaker terminals Is BePIOx So
have passed, the relay takes 7 — 40 seconds +o start.
Vrms.
activating. Next, change the polarities of the dry bat-
Under these conditions, 'shoréelreuit the Speaker. ter- "
teries and carry. out the above mentioned operation me
minals of the channel to which the input signalisap-
check the operation of the relay.
|
_ plied using a lead wire, etc. If this short-circuit makes
If the relay is energized with. 'this 'operation, it means
the ASO detection circuit operate, No output appears 2S.
that.' the. speaker, protection: circuits are functioning
short-circuiting is removed.
—.
When conducting 'this eperional: check. ce. care not
Next, turn off the power switch and, after appr Ox. x10 ___..
to create shortcircuits
with parts close athand.
|
"sec., turn the power switch on again. When output
ea
a
o e
A
a
eee
ee ae
comes. out of the speaker terminals, 'this aneleales
that the ASO detection circuit is operelne ae
_@ Phenomena and remedy when the protection circuit operates
| PRenamenon when the protection. mn
nee
| Type-of protéction Sreui .
" circuit operates —
7
|
Muting circuit
"No sound comes out about 7—10
| Normal:
0 7
er ee
a
ae
|
'sec. after ne pewer' switch i Is -.
Ta
ren S
turned ON.
|
ae
|
|
| 2
| Protection circuit it of t the.
No sound comes Out.
a
Short. circuit of speaker | Turn off the power switch, check ae
:
ee \Geton transistors :
2: When the power switch is.
.| Output terminal.
=
| whether the speaker terminal is short»
turned ON, the relay becomes -
.. ON, then OFF when i eda
is applied.
| circuited or not, and turn ON again. - [
1. No sound. comes out.
is
4. 2. Neutral point voltage: is more
0
than
#42
V o
ee
3. After the power switch is
tuiped ON, ateiay ae t.turn
ON.
| Speaker protection circuit
'ls
(DC voltage detec-
| Power amplifier faulty, |
ie tion/ protection circuit)
~ Repair faulty parts in power amplifier.
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