JBL 8, Service Manual, Page: 7 / 16

6
Powered Subwoofer ARC SUB 8
H. If signal present at pin 8, but still no sound, check
for cold solder joints on all power resistors, R4a and
R4b and the the power amp module. If C24 is
blown, C6 is not soldered or is defective. Check the
signal at R2. On the down signal side, the voltage
signal should be very small. If signal is similar on
both sides of R2, the amp module is likely defective.
I. If you hear a mechanical clicking noise from the amp
module, this indicates that the short circuit protection
has been engaged. Check that Q3, Q4 and Q5 are
soldered correctly. Also check that Q3 is not shorted
to power amp case.
J. If you have to replace the power module, be very,
very patient with the solder removal from this single
sided PCB. COMPLETELY REMOVE SOLDER
BEFORE TRYING TO REMOVE THE MODULE!
K. Assembly notes. Top side soldering as below:
J5: solder both ends
J3: solder both ends
J1: solder both ends
R48: solder GND end
At junction of C7a/C7b: Pin to GND
Crossover pot Gnd wire from PDB pad to POT
barrel. (Only physical contact required between
pot body and faceplate).
After repair, inspect for possible safety hazards, including
loose hardware, missing lock washers, correct fuse and lead
dress of primary wires (these must be held in position with
cable ties so that they cannot touch secondary components).
With ohmmeter, check that panel is connected to signal
ground.
It is essential that the following safety insulation test be
performed prior to returning the Power Sub-Woofer to the
customer, using one of the following methods.
A) Insulation Resistance Test
With a 500VDC Insulation Tester, Check
insulation from the outer metal contact of the
RCA jack (chassis) to the line neutral of AC
cord. Resistance should be >100M
Ω
.
B) Hi-Pot Test
If a UL approved Hi-Pot tester is available, test
line & neutral of AC cord to outer shell of RCA
jack (chassis) at 1100VAC for 2 seconds.
Observe all of instrument manufacturer’s
instructions and safety warnings in performing
this test.
Connect sub-woofer system to a music source. Play at high
level while checking for air leaks around panel edge, driver,
panel jacks and controls, and voice coil problems such as
rubbing or loose turns. With the crossover "frequency" set to
50Hz, very little of the voice content should be heard.
4. REASSEMBLY
Follow all disassembly instructions in reverse order. If the
input plate has been removed, it must be re-sealed with a small
bead of silicon seal or air leaks may result.
5. LIST OF SAFETY COMPONENTS
REQUIRING EXACT REPLACEMENTS
F1 Fuse SLOW BLO 0.5A 250v T type
UL approved
CMC1 mc4438 Neosid 28-52, 2x 2.2mH
#23 awg @ 2x 24
L1 mc4436 Neosid 32-19 200uH
#18SNSR @36
T1 Transformer #4300, Use only factory
replacement
PWR CORD SPT-2 better with polarized plug,
UL appoved wired with the hot side
to fused side. Use with UL approved
panel strain relief only.
BDR Bridge Rect. 200V 4A Use only factory
replacement.
C1, 2 3300uF, 50V Electrolitic Radial.
Be sure replacement part is at least the
same working voltage and capacitance
rating. Also the lead spacing is
important. Incorrect spacing may
cause premature failure due to internal
cabinet pressures and vibration.
C6 10u 50V Electrolytic Radial.
R29 470
Ω
0.25 +-1% Metal
S53AMI Power Amp Module