The Hewlett-Packard Model 6235A Triple Output Power Supply is a compact, general-purpose bench supply designed for powering developmental IC circuits, both linear and digital. It combines two 0 to ±18V tracking outputs rated at 0.2A with a single 0 to +6V output rated at 1A. The ±18V tracking outputs can also be used in series as a single 0 to 36V, 0.2A output.
Function Description:
The power supply provides three independent outputs: one 0 to +6V output and two 0 to ±18V tracking outputs. Connections to the outputs are made via binding posts on the front panel. The +6V and ±18V outputs share a common output terminal, which is isolated from chassis ground. The chassis ground terminal is located on the supply's rear heat sink assembly. Each output is protected against overload or short-circuit damage by separate fixed current limit circuits. The +18V and -18V outputs are each limited to 0.255A ±15%, and the +6V output is limited to 1.275A ±15%.
Important Technical Specifications:
- DC Output:
- Voltage span: Variable using front panel controls.
- Minimum operating voltage for each output: ≤ 50 millivolts.
- 0 to +6V Output: Maximum rated output current is 1A. Short circuit output current is 1.275A ±15%.
- 0 to ±18V Output: Maximum rated current is 0.2A for each output. Short circuit output current is 0.255A ±15%. Unbalanced loads within current rating are permitted.
- Input Power:
- Standard Option: 104-127Vac (120Vac nominal), 47-63Hz, single phase.
- Option 028: 208-250Vac, 47-63Hz, single phase.
- Maximum input power: 35 watts (high line, full load conditions).
- Load Effect (Load Regulation):
- 0 to +6V Output: 8mV for a load current change equal to the current rating.
- 0 to ±18V Outputs: 10mV for a load current change equal to the current rating.
- Source Effect (Line Regulation):
- 0 to +6V Output: 8mV for any line voltage change within rating.
- 0 to ±18V Outputs: 15mV for any line voltage change within rating.
- PARD (Ripple and Noise):
- All Outputs: Less than 1mV rms and 5mVp-p (20Hz to 20MHz).
- Load Transient Recovery Time:
- All Outputs: Less than 50µsec for output recovery to within 15mV of nominal output voltage following a load change from a full load to half load (or vice versa).
- Temperature Ranges:
- Operating: 0 to +40°C ambient. From 40°C to 55°C, output current is derated linearly to 50% at 55°C.
- Storage: -40°C to +75°C.
- Meter Ranges:
- 0 to +6V Output: 0 to 7V, 0 to 1.2A.
- 0 to +18V Output: 0 to 21V, 0 to 0.24A.
- 0 to -18V Output: 0 to 21V, 0 to 0.24A.
- Meter Accuracy:
- Voltmeter: All Outputs: ±3% of full scale.
- Ammeter: All Outputs: ±4% of full scale.
- Weight:
- Net: 5 lb (2.3 kg).
- Shipping: 7 lb (3.2 kg).
- Supplemental Characteristics (Typical Performance at 25°C ambient):
- Load Regulation: 0 to +6V Output: 4mV; 0 to ±18V Output: 6mV.
- Line Regulation: 0 to +6V Output: 4mV; 0 to ±18V Output: 6mV.
- Ripple: All outputs: 0.2mV rms.
- Tracking Accuracy (±18V Outputs): Remains constant (within 1%) over 1 to 18 volts for any TRACK control setting.
- Temperature Coefficient: Less than 0.04% + 2mV voltage change per degree Celsius over 0 to 40°C after 30 minutes warm-up.
- Drift (Stability): Less than 0.1% +10mV (dc to 20Hz) during 8 hours at constant line, load, and ambient after 30 minutes warm-up.
Usage Features:
- Front Panel Controls: Voltage controls, output terminals, and a combination voltmeter/ammeter are located on the front panel.
- Voltage Controls: One control sets the 0 to +6V output, and another simultaneously adjusts the 0 to +18V and 0 to -18V dual tracking outputs. A tracking ratio control sets the ratio between the +18V and -18V outputs, allowing the negative supply's output to be set from less than 0.5V to equal the positive supply's output. A 1:1 ratio is useful for balanced positive and negative voltages.
- Metering: A line pushbutton switch with a simulated (non-electrical) on-off indicator and four meter select pushbutton switches are provided. One meter pushbutton selects either voltage or current monitoring, and the remaining three pushbuttons select the output to be monitored and the proper meter range.
- Line Voltage Options: Available with standard 104-127Vac, 47-63Hz input, and a 240Vac nominal line voltage option (Option 028). The supply is furnished with a permanently attached 5-foot 3-wire grounding type line cord.
- Load Connections: All output terminals are isolated from chassis ground. The +6V and ±18V outputs use a single common output terminal. This common (COM) terminal or any other output terminal can be grounded to the chassis ground terminal. Loads can be connected separately between each 0 to 18V output terminal and the COM terminal, or between the +18V and -18V terminals for a 0 to 36V output. A single load can also be connected between the +6V and -18V terminals for a 0 to 24V output.
- Parallel Operation: Two or more power supplies can be connected in parallel to obtain a total output current greater than that available from one supply.
- Output Capacitance: An internal capacitor helps supply high-current pulses of short duration during constant-voltage operation. External capacitance can improve pulse current capability.
- Reverse Voltage Protection: Internal diodes protect output electrolytic capacitors and driver transistors from reverse voltage.
Maintenance Features:
- Line Voltage Conversion: The user can convert the unit from one line voltage option to another by resetting an internal line voltage selector switch (S2), replacing the fuse and line cord plug, and changing the line voltage label. The selector switch is mounted on the circuit board behind the meter.
- Fuse Replacement: The ac line fuse is in an extractor type fuseholder on the rear heatsink. Correct fuse ratings are 0.4A slo-blow for 120Vac input and 0.2A slo-blow for 240Vac input.
- Overcurrent Protection Adjustment: Current limits are set by adjusting resistors R3 (for +18V), R13 (for -18V), and R23 (for +6V).
- Calibration: Procedures for current limit adjustment and meter calibration are available in the manual.
- Troubleshooting: A dedicated section in the manual provides troubleshooting procedures and guidance for open fuse troubleshooting.
- Repair and Replacement: Instructions for series regulator replacement and semiconductor replacement are included.
- Repackaging for Shipment: Original packaging materials are reusable. If unavailable, contact Hewlett-Packard for materials and instructions.
- Safety Considerations: The product is a Safety Class 1 instrument. Users are advised to review safety markings and instructions before operation. Ensure proper protective earth grounding to prevent potential shock hazards. Only use fuses with the required rated current and specified type.
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