SECTION IV
OPERATION
Should a fuse bloVli instantly, it indicates a high current short in
the 12VDC Iine. Either in the supply, the poV\,ercable to the am-
plifier, or in the amplifier itself. The first step should be to un-
plug the power cable from the amplifier, remove the top cover
from the power supply for access to the terminal strip and with the
aid of a short jumper wire, connect terminal No.5 in the supply
to the car frame. This will normal'ly start the supply (replace fuse
blown in above test). If the supply does start when shorting ter-
minal I~O. 5 to the frame and the voltage output~is as it should
be, it v;ouldindicate the short is in the Bi-Linear Ampl ifier. If
the supply' blows another fuse, you can isolate the cable as a
source by disconnecting all cable wires at the supply terminal
strip and again starting the supply by jumping terminal No.5 to
the car frame (replace the blown fuse). If the supply operates
normally, then the trouble is in the cable. If another fuse is blown
, _ , . ,.' the trouble is in the supply. Removethe supply and very care-
A specIal hermal Rel~l-ncmded+"tbL'L J 1.' ~o_o_ffe~ __, fully look for components that might be touching the case and
the user maximumprotection from temperature failure of compon- ------cau-sing'En;fturt-.-----1+--RoAELQ[-.EJob2..erved,then itis reasonably cer-
ents, especially transistors. If a nominal temperature of 176 de- tain the trouble is a bad transistor-~-------
grees is exceeded, this protective device will open the primary
relay 1<1and render the supply inoperative until the temperature
drops to a safer level, at which time it will automatically reacti-
vate the supply.
Operation of the Model 602 Power Supply is controlled by the aNI
OFFSwitch of the Model 600 Bi-Linear Amplifier. Whenthe Mod-
el 602 Power Supply is operating properly, there will be a slight-
ly 'audible. tone of approximately 400 cycles heard near the
Power-S·upply. Due to the heavy power drain on the automotive
electrical system by this Power Supply when (>perating only use
it when the motor is in operation. Usage of the Power Supply
without the engine in operation can cause damage to the transis-
tors due to low voltage conditions.
Power SURplydamage is most likely to occur by continuing oper-
ation or usage after driving the vehicle for a considerable period
of time and then stopping and turning off the motor. The temper-
ature rise within the motor compartment is rapid and wi II cause
transistor failure or operation of the thermal relay. Under such
conditions the Power Supply should be turned off unti I the car is
moving again or until the motor compartment has cooled down.
The majority of transi stor fai Iures are traceable to usage of the
equipment after extended driving periods while the car has stop-
ped for refuel ing, etc.
Loss of operation during a transmission due to this relay is cer-
tainly more desirable than loss of operation due to transistor
failure. Proper mounting in a well ventilated area will prevent
loss of operation due to either of the above causes, barring other
factors of unusual natural heat. .
The 602 power s~1' fl'y is further protected from over load damage
by a fuse in the negative return load of the high and low voltage
sections. This fuse is located on the side opposite the primary
40 amp fuse. It is a size AGe 0.5 amp fuse. Failure of this
fuse while tuning up or operating indicates an overload which
could cause 602 power supply fai lure or secondary component
failure.
DO NOT use a larger fuse. Use onlv type AGe
0.5
amp.
An occasional fuse failure is much less inconvenient than
transistor or torroid transformer failure.
Use onlv AGU-40 fuses in the primary Power SupplV line.
A higher amperage fuse will not protect the supplV from
damage.
In most cases, when the 40 ampere fuse blows, it indicates a
strong probabiIity of a shorted transi stor. However"-sometimes a
surge can blow a fuse without damage occuring an~Ja new fuse
should be installed and tried before further investigation is made.
If the supply operates normally, then it indicates nO,damagewas
done. If it instantly blows the new fuse, it is most likely an in-
dication of a bad transistor, a short in the primary cables, or a
short in the power cable.
The following ohecks can be made to isolate va}ious problems
that might be encountered and speed servicing in tr:iefield. How-
ever, V',e suggest that no work be done in the field unless you
anticipate completing the work in the field.
When a bad transistor is the conclusion of the tests made, it can
be verified with a simple VOM test, using a low ohm scale which
will read 5 ohms or less. To make the test. disconnect the two
wir~s to the lugs of the transistor (use long nose pliers to hold
the lugs near the case and prevent overheating the transistor) and
measure resistance between the two lugs. It should be at least
3 ohms. A bad transistor will show a direct short. If good, im-
mediately reconnect the wires, taking care not to reverse them,
use the pliers again for a heat sink. Check the other transistors
and replace the one found shorted. While replacing the defec-
tive transistor, aIways check the four 1.5 ohm
I
5 watt base
drive resistors for proper value. If all transistors are found to
be good, it would indicate a short circuit in the other power sup-
ply components, such as a diode, capacitor or toroid transformer.
If the emitter current equalizing wires, R9- R12, have been
damaged, do not replace with any other size and length
wire or improper current distribution will cause transistor
failure again. Use
6
of
#22
AWG wire onlv.
If the fuse does not blow and the lamp and fi laments light.
but the power supply does not start osci lIating, the type
111495 bulb should be checked to insure the filament has
not burned out. The type 111495 is an aircraft lamp avail-
able from most aircraft repair shops. If not locally avail-
able, type 111458 can be substituted, but the filament is
not as rugged as the type 111495. ;
