Model 865-A Deep Sea Acoustic Release/Transponder M-855-009
Benthos, Inc.
18
5.2 Electrical Parts
5.2.1 Battery Packs
The standard battery pack consists of 18 alkaline 'D' cells arranged in two parallel strings of 9 cells each.
These strings have an open circuit voltage of 13.5 volts when new and are tied together through isolation
diodes on the battery pack connector board. The isolation diodes serve to protect the good string in the
unlikely event that one string fails. Thus, there is redundancy designed into the battery pack.
The battery pack is easily replaceable in the field. No soldering is required. See Section 7.1 for step-by-
step instructions.
Replacement battery packs are available from stock at Benthos at very reasonable prices.
5.2.2 Electronics Chassis Assembly (Part No. D-855-73)
This modular assembly includes the battery tube, electronics tube, chassis end plates, connectors and
circuit boards. The battery pack fits snugly into the battery tube and the circuit boards are protected by
the electronics tube. When installed, a connector on the motor mates with a connector on the chassis
assembly, thus providing circuit paths to the switches on the end cap assembly. Also, a connector on the
top end automatically mates with the transducer when the housing is closed. Locating pins serve to align
all connectors and prevent incorrect insertions.
Two circuit boards are installed back to back with a connector in between. All critical signals are double
pinned on this connector for the highest possible reliability.
5.2.2.1 865-A Board No. 1 (Part No. C-855-130)
Board No. 1 contains all the large components required for transmitting, i.e. output transformer, inductor,
power transistors and capacitors. It also contains the circuitry for transmit pulse gating, and the sensitive
receiver preamplifier. The transducer is connected to this board.
To remove Board No. 1, power OFF, disconnect the transducer connector, then remove the four corner
screws and unplug the board (see Figure 5-2).
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