User manual SOUNDCRAFT CPS800 POWER SUPPLY

[. . . ] Soundcraft shall not be liable for any loss or damage whatsoever arising from the use of information or any error contained in this manual, or through any mis-operation or fault in hardware contained in the product. No part of this manual may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, electrical, mechanical, optical, chemical, including photocopying and recording, for any purpose without the express written permission of Soundcraft. It is recommended that all maintenance and service on the product should be carried out by Soundcraft or its authorised agents. Soundcraft cannot accept any liability whatsoever for any loss or damage caused by service, maintenance or repair by unauthorised personnel. Harman International Industries Ltd. [. . . ] This greatly reduces the dissipation in the supply in protection mode. This system accomplishes its task, but can give trouble as the supply may work perfectly into a resistive test load but not start into a real console load. The problem is that a mixing console is essentially a constant-current load; as the supply voltage is increased, almost the full current is drawn when only 2 or 3 volts are applied. There are thus two stable states, with rails normal and the full current drawn, or with the supply shut down to the few volts that will cause the foldback current to flow. When the supply is switched on, it tends to stick in the second of these two states. The CPS800 POWER SUPPLY avoids this problem by implementing constant-current protection that causes complete shutdown (rather than foldback) after a fixed time delay. This is described for the +17V supply; the -17V supply operates identically. The first part of the problem is to measure the output current without dropping 0. 6V across a resistor to turn on a protection transistor. At 16 Amps the losses in this drop would be unacceptable. Therefore supply current is measured by the voltage drop across 0. 05R resistors (R35, 36 in parallel) which carry a quarter of the output current and so drop 200 mV at full load. This is compared with a 200mV reference voltage across R86, derived from bands-gap reference IC8 which sits on the output rail, by differential amplifier TR18, 19. The thermal sensor on the RH heatsink is LM35DZ TR31. It outputs 10mV per degreeC above freezing point (0 degC) and applies it to IC5-B non-inverting input. IC5-B is used as a comparator, with R114, 106 giving a small amount of hysteresis to prevent dither or oscillation. IC reference TR29 produces a stable 1. 237V which is reduced to 1. 00V by R104, 112. This is applied to the inverting inputs of IC5-A, B as the shutdown temperature reference, and represents 90 degC at the TO3 can top*. TR27 senses the temperature of the LH heatsink. * Temperature shutdown takes place at 100 degC on some earlier issue PCB's. If either heat sensor exceeds 100 degC the output of the associated op-amp goes high, applying voltage to the top of R109, and enabling the relaxation LED-flashing oscillator IC6-B. If JMP2 is fitted in the "ON" position, shutdown of the +/-17V rails is also implemented. TR30 is turned on via R117, which turns on TR28, and shuts down the -17V supply. The mutual shutdown system then also shuts down +17V. [. . . ] AP1357 Parts List 31 R11 R12 R13 R14 R15 R16 R17 R18 R19 R20 R21 R22 R23 R24 R25 R26 R26 R27 R28 R29 R30 R31 R32 R33 R34 R35 R36 R37 R38 R39 R41 R42 R43 R44 R45 R46 R47 R48 R49 R50 R51 R52 R53 R54 R55 R56 R57 R58 R59 R60 R61 R62 R63 R64 R65 R66 R67 R68 R69 R70 . AP1345 32 Parts List R71 R72 R73 R74 R75 R76 R78 R79 R80 R81 R82 R83 R84 R85 R87 R88 R89 R90 R92 R93 R94 R97 R98 R99 R100 R101 R102 R103 R104 R105 R107 R108 R109 R110 R111 R112 R113 R114 R115 R116 R117 R118 R119 R120 R121 R122 R106 REG1 REG2 REG3 TR2 TR8 TR9 TR10 TR16 TR18 TR19 TR20 TR21 TR22 . BD0301 Parts List 33 TR23 TR24 TR25 TR27 TR28 TR29 TR30 TR31 . BD0301 MISCELLANEOUS HARDWARE Description . [. . . ]