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B+K Precision Model 1686 DC Power Supply

Power your 12-volt equipment with this rugged supply.

Whether powering a prototype circuit or providing power for equipment being serviced, the bench-top DC power supply is an essential tool for anyone in the electronics industry.

Its also essential for any anyone who plays an active role as an electronics hobbyist. B + K Precision ( 6470 W. Cortland St., Chicago, IL 60635) has recently introduced the Model 1626, a supply that is ideal for powering equipment rated at 12 volts.

The 1686 can deliver an output from 3 volts to 14 volts DC with a maximum current of 12 amperes.

That high current rating is sufficient to power most car stereo systems, even those with high-power amplifiers. Most mobile amateur radio equipment, as well as CB transceivers, marine radios, and other high-current automotive accessories can be powered safely from the 1686.

The maximum output current available from the power supply is proportional to the output voltage.

When the supply is set to deliver 13.8 volts-which is the operating voltage for most equipment nominally rated at 12 volts--the 1686 can deliver 12 amperes continuously to the load. That drops to 10 amperes at 12 volts, 4.5 amperes at 5 volts, and 2.5 amperes at 3 volts.

At all voltage settings, the specified load regulation is less than 0.8% That is, regardless of the load at the output terminals, the supply's output voltage will deviate less than 0.8% from its initial setting. The line regulation of the supply is also rated at 0.8% from 108-132 volts AC.

That means that regardless of the change in the line voltage to which the supply is connected, the output voltage will deviate less than 0.8%.

The ripple and noise is specified a less than 10 millivolts rms. Overload current limiting provides protection against excessive overload or short-circuit output.

The 1686 is housed in a black metal cabinet that measures about 5/2 x 6 x 12 inches; it weighs jus over 12 pounds. The front panel features a pair of easy-to-read analog meters along the top edge, one for voltage and the other for current--that provide an indication of what the supply us doing at a glance. To the right of the meters is a rotary knob that controls the output volt age. The bottom half of the panel contains two sets of output connectors, a power switch, and two LED indicators.

The main voltage output is provided on a set of binding posts. Two sets of spring-loaded terminals--much like the kind commonly found on audio speakers--are provided for connecting low-current loads.

The tie points can supply a maximum of 2 amperes. Above the power toggle switch is an LED that serves as a power-on indicator.

Above that is an LED that indicates that the supply is in an overload condition and has reduced its output voltage.

The rear panel contains a fuse holder and a small fan. The fan, which helps to keep the supply compact by reducing the size of the heatsinks needed, does not run constantly. Rather, it is controlled by a thermostat, and comes on only when the internal temperature of the supply is too high for safe operation.

The outputs of the supply are isolated from the chassis and earth grounds, which is essential for flexibility in connections. If required, for example, the positive output can be connected to ground for powering positive ground automotive equipment.

The isolated outputs also allow multiple supplies to be connected together in series or parallel for powering equipment that has higher voltage and current requirements.

For example, connecting two supplies in parallel will provide a continuous source of 24 amperes, while connecting two supplies in series will provide an adjustable 6 to 28-volt power supply.

The model 1686 can operate from either 120-volt or 230-volt AC power lines with frequencies of 50 or 60 hertz. A slide switch on the bottom of the chassis permits easy selection.

We found the operation of the model 1686 to be quite straightforward. The manual supplied with the supply was more than adequate, and we were happy to find that calibration instructions were included there.

B +K Precision has priced its model 1686 at $199. We think that the supply is ideal for service shops that regularly repair mobile equipment, as well as for retailers who need to power equipment on display. Of course, radio amateurs will also appreciate the 12-ampere continuous duty rating.

Also see: RC Filters

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