T962 PreAmp Power Supplies ------------------------------ Original Rev. 15-NOV-2007 Current Rev. 16-Sept-2008 The power supplies for the PFC-16 preamplifier cards are in two chassis in the DAQ rack. Each of the preamplifier card files in the preamp box has its own power supply chassis, i.e. there are two power supply chassis in the full system. Each preamp power supply chassis must operate 15 preamp-filter cards, i.e PFC-16 cards. The expected load per power supply chassis is: Load Load Load per Card File Power per PFC-16 per PFC with Supply Channel Card 15 PFC Cards ----------- ---------- ---------- ------------- Preamp +8V 14.0 mA 224 mA 3.360 Amps Preamp -6V 3.5 mA 56 mA 0.840 Amps Filter +5V 38.7 mA 619 mA 9.288 Amps Filter -5V 38.7 mA 619 mA 9.288 Amps Total Watts 0.52 Watts 8.32 Watts 124.8 Watts Linear power supplies are used to simplify the task of achieving the low noise level power that is necessary for the preamp filter cards. - The Preamp +8V comes from a 12 Volt 10.2 Amp power supply Power One model number: HE12-10.2-AG. This power supply must be modified to supply a nominal 8 Volt output as described below. HE12-10.2-AG (Lead Free) is 179-2340-ND @ $115.00 - The Preamp -6V comes from a 5 Volt 6 Amp power supply Power One model number: HC5-6/0VP-A. This power supply must be modified to supply a nominal 6 Volt output as described below. HC5-6/OVP-AG (Lead Free) is 179-2325-ND @ $57.50 - The Filter + & - 5 Volts will come from 5 Volt 18 Amp power supplies Power One model number: HE5-18/0VP-AG. HE5-18/0VP-AG (Lead Free) is 179-2344-ND @ $151.00 Fuses in the Power Supply Chassis: AC Input DC Output Supply Model Fuse Fuse ------------ ------------ -------- --------- +8V Preamp HE12-10.2-AG 3 Amp 15 Amp -6V Preamp HC5-6/OVP-AG 1 Amp 3 Amp +5V Filter HE5-18/0VP-AG 3 Amp 15 Amp -5V Filter HE5-18/0VP-AG 3 Amp 15 Amp Modifications to the Individual Supplies in the Power Supply Chassis: +8 Volt Preamp Supply Convert the HE12-10.2-A supply to make a nominal 8 Volt output by doing the following: Add a 0.5 Ohm 25 Watt resistor in each leg of the main secondary winding of the power transformer. The intent of these resistors is to reduce the added heat load on the pass bank transistors caused by the increased voltage drop across them. These resistors also improve a little the filtering that is accomplished by the bulk DC filter capacitor. These two resistors are mounted to the end of the power supply frame with screws and heat conduction paste. Replace R11 which is normally a 2.2k Ohm resistor with a 220 Ohm resistor. Just bridge the 2.2k with the 220 Ohm part. R11 is a feedback resistor to the uA723 regulator chip. The current through R11 is still small because it is in series with the 4.7 k Ohm resistor R12. -6 Volt Preamp Supply Convert the HC5-6/OVP-AG supply to make a nominal 6 Volt output by doing the following: Replace R11 which is normally a 3.6k Ohm resistor with a 7.5k Ohm resistor. Remove CR6 to deactivate the over voltage protection which otherwise would fire the crowbar SCR at about 6.0 to 6.2 Volts. Operating this 5 Volt supply to make a quiet 6 Volt output has some risk because there is only about 10 Volts of bulk DC at the input of the pass bank. Things should be OK because: the -6 Volt supply will not need to put out any more than 6 Volts (the drops in the long DC power cables running to the preamp box actually work in the direction to reduce the output required from this supply while still giving a full -6 Volts to the preamps) and because this supply is well oversize - it is a 6 Amp supply that should only need to deliver 0.84 Amps. +5V and -5V Filter Supplies - no modifications are needed Safety Interlock with the Air Blower ------------------------------------ The Preamp Power Supplies do not have any AC line power until they receive an interlock control voltage from the preamp air blower. This interlock signal is a 12V DC signal that comes from a small power supply in the preamp air blower unit. Resistors in this power supply limit the current available on this control signal to a few tens of mA. In each Preamp Power Supply chassis this interlock control signal is used to close a solid state relay which then delivers AC line power to the preamp power supplies. The solid state relay used in each Preamp Power Supply chassis is a Crydom model CWD2425S. It is rated to handle 240 VAC at 25 Amps. Remote Sensing -------------- Because of the constant load presented by the PFC-16 preamp cards these Preamp Power Supplies do not use remote sensing. Once installed the power supply output voltages can be adjusted to deliver the nominal Preamp +8V and -6V and the Filter +5V and -5V at the Preamp Box. Variation of even a couple of hundred mVolts will not greatly effect the operation of the PFC-16 cards. Preamp DC Power Cable Connections --------------------------------- The Preamp Power Cable that runs from the Preamp Power Supply over to the Preamplifier Box uses 4 contact Chinch Jones connectors to plug into the Preamplifier Box. There are separate connectors for the Preamp Vcc Vee power and for the Filter Vcc Vee power. The Preamp Power Cable uses #14 AWG 105 deg C wire with the following colors: Preamp Vcc Red Filter Vcc Yellow Preamp Vee White Filter Vee Orange Preamp Return 2x Black Filter Return 2x Black The Chinch-Jones connectors used on the Preamp Power Cables are: The cable connector is a Chinch S-2404-CCT socket connector. Mounted in a cutout in the Preamplifier Box is a Chinch-Jones P-2404-AB plug connector. All connectors are wired: Vcc on pin #15 Vee on pin #16 Return is on pins #13 and #14 and the alignment pin Power Connectors to the PFC-16 Cards ------------------------------------ - PreAmp Power Connector The preamp power connector is a 6 pin 2x3 header without walls. It has the standard pin numbering with pin #1 in the upper right-hand corner and pin numbers alternating the two rows as you move along the connector. The preamp power connector has the following pinout: Pin Power Cable Pin Power Cable Num Supply Color Num Supply Color --- -------- ----- --- -------- ----- 1 PAMP_VCC Red 4 GROUND Black 2 PAMP_VEE White 5 PAMP_VEE White 3 GROUND Black 6 PAMP_VCC Red - Filter Power Connector The filter power connector is a 6 pin 2x3 header without walls. It has the standard pin numbering with pin #1 in the upper right-hand corner and pin numbers alternating the two rows as you move along the connector. The filter power connector has the following pinout: Pin Power Cable Pin Power Cable Num Supply Color Num Supply Color --- -------- ------ --- -------- ------ 1 FLTR_VCC Yellow 4 GROUND Black 2 FLTR_VEE Blue 5 FLTR_VEE Blue 3 GROUND Black 6 FLTR_VCC Yellow