Fender Acoustasonic Junior Service Manual - page 2
ACOUSTASONIC JUNIOR
SPECIFICATIONS
Product Release No.:
PR 334
(This is not a model number)
Part Number:
120V Version 22-1302
240V Aust
22-1332
230V UK
22-1342
230V EUR
22-1362
100V
22-1372
Power Requirements:
100V Version: 100 VAC, 50/60 Hz, 300W
120V Version: 120 VAC, 60 Hz, 300W
230V : 230 VAC, 50 Hz, 300W
240V Version: 240 VAC, 50 Hz, 300W
Power Amplifier Section
Power output:
40 Watts RMS per channel, (80W RMS Total)
into 8 ohms @
Sensitivity:
640 mV @ stereo effects return (both channels)
Preamp Section
Input Impedance:
10 M
Ω
(inst), 3.6 k
Ω
(Mic), 36.4 k
Ω
(Line/Inst)
Sensitivity For
Full Power:
12.75 mV (Inst), 5 mV (Mic), 50 mV (Line/Inst)
Tone Controls:
Treble +/- 15dB @ 15kHz (Inst) & (Mic/Line/Inst)
Mid +/- 12dB @ 1 kHz (Inst)
Bass +/- 12dB @ 100Hz (Inst), +/- 12dB @ 50Hz (Mic/Line/Inst)
Feedback Notch:
-10dB from 80Hz to 700Hz (Instrument Channel)
String Dynamics:
0 to -15dB @ 6.3kHz (Instrument Channel)
Phantom Power:
+15VDC (Mic)
Speaker Complement:
Two 8 Ohm Special Design 8" Speakers (P/N 051016)
Single Piezo Horn (P/N 049260)
Dimensions:
Height:15.5"
(39 cm)
Width: 22.4"
(57 cm)
Depth: 10.2"
(26 cm)
Weight:
43 lbs.
(19.5 kg)
Product specifications are subject to change without notice
ACOUSTASONIC JUNIOR
THEORY OF OPERATION
L.Spkr
R.Spkr
L
Pwr
Amp
R
Pwr
Amp
Phase
Select
(+)
(-)
(+)
(-)
Stereo
EFX
Send
Stereo
EFX
Send
Stereo
EFX
Return
Stereo
EFX
Return
(L)
(R)
Reverb
Chorus
Switching
Logic
(Note 1)
Footswitch
Inst
Line/Inst
Mic
Gain
Gain
Notch
String
Dynamics
EQ
Bass
Mid
Treble
Ch. 1
Preamp
Ch. 2
Preamp
(+)
(-)
Phase
Select
EQ
Treble
Bass
Feedback
Notch
Filter
String
Dynamics
Return
Send
Mic
Reverb
Send
Master
Reverb
Rate
Depth
(S2)
Chorus
in/out (Note 2)
Note 1: S1=Ch. 1 Reverb out/in
S3=Ch. 2 Chorus out/in
Note 2: S4= Master chorus out/in is over-ridden
by the footswitch being plugged in.
(S5)
U10A
U10B
Fig. 1 Block Diagram
Mono
Effects
Loop
The
Acoustasonic Jr.
is a very different kind of guitar amplifier. The following discussion will introduce the service
technician to it's unusual organization and features (refer to Fig. 1):
INSTRUMENT CHANNEL
The
Instrument Channel
(Ch. 1) is implemented with operational amplifiers, and has some very useful features:
a)
The
Feedback Notch Filter
provides a 10 dB reduction at the center frequency (which is sweepable
from 80 Hz to 700 Hz.) This easily controls the most common feedback frequency of 240 Hz.
b)
The
String Dynamics
circuit provides a way of varying the amplitude of the 6.3 kHz region of the
overall frequency response (to compensate for a sometimes-present harshness of the piezo pickups.)
2