STANDBY BATTERY SUPPLY (1A4) (P/N 6025-1008)

TM 11-5820-918-13

the synthesizer logic. The unregulated +35 VDC supply is applied to the frequency

standard module and the programmer test logic.

NOTE

For units with a rechargeable battery supply (paragraph 4- 37), +35

VDC is also supplied to the battery charging circuit.

4-35. An internally mounted toggle switch is provided for switching between 120 and

240 VAC inputs. In addition, compensation for small increments of input line voltage

variations can be made with jumpers on a terminal board mounted adjacent to the trans-

former primary.

4-36. STANDBY BATTERY SUPPLY (1A4) (P/N 6025-1008). The non-rechargeable

battery consists of 18, 1.5-volt batteries. The supply (approx. 29 to 15 volts de-

pending on battery condiditon) is used to drive the switching regulator and the

crystal oscillator located in the frequency standard module 1A3 if the main power is

interrupted. A test circuit, located on the programmer circuit card 1A2A1, measures

the output voltage of the battery supply and yields the results necessary to drive

the front panel indicators. (Refer to paragraph 5-26 for battery test conditions.)

A5 amp fuse, located within the supply, provides protection for inadvertent shorts.

4-37. RECHARGEABLE STANDBY BATTERY SUPPLY (1A4) (P/N 6025-1018). The

rechargeable battery supply (figure FO-19) is used to maintain timing synchroni-

zation, blanker frequency memory and the 5 MHz frequency standard in the event

of power cut-off. The supply consists of 12 sealed lead/acid batteries, rated 2-volts

each, and a voltage regulator circuit card. The supply is contained in a sliding

drawer. Standby power of 28-volts DC is supplied to the 10245 MHz frequency stand-

ard and to a switching regulator which provides +5 volts DC to the programmer timers.

4-38. The regulator card, mounted in the battery box, receives unregulated +35 VDC

input from the 1024 power supply. Voltage regulator U1 (figure FO-19) is set to out-

put exactly 28.9 VDC by potentiometer R3. The resulting 28.9 volts at TP1 provides

a precise terminal voltage (28.2 volts) for the batteries at the manufacturers recom-

mended trickle charge rate of approximately five milliamps. The 6.8 ohm resistor,

R4, limits the charging current to a safe value (400 mA max.) when the batteries are

discharged. The 2-amp fuse, F2, prevents severe physical damage to the system wir-

ing harness or battery box if an inadvertent short occurs on the 28 volt line. Fuse

F1 protects the 1024 power supply from shorts in the battery charging circuit. Per-

manent damage to the batteries may occur if they are allowed to completely discharge

to 0 volts. Relay coil (K1) and zener diode (VR1) sense the battery voltage. If the

voltage drops below 19 volts, relay K1 drops out (opens) removing the battery load.

Turning the AC line power to the 1024 back on automatically resets (closes) the relay

and activates the battery charger circuit to recharge the batteries. Depressing switch

S1 forces the relay to drop out when the batteries have normal charge and the AC

line power is off. This allows the batteries to be disconnected from any load for long

term storage. Refer to paragraph 3-16 for additional storage information.