User manual LINN LK275 SERVICE MANUAL

[. . . ] Service Manual for LK2 Series of Power Amps Covering LK2(60), LK275 & LK280 For the purposes of this manual, we will refer to the three types as LK260, LK275 & LK280. The term LK2 will be used as an "umbrella term", covering all three types, i. e. the LK2 series. CONTENTS INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 ABOUT THE LK2 SERIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [. . . ] If the fuse remains intact, the fault is more likely to be on the board. Bridge rectifier diode on amplifier board faulty (probably internally short circuit). These are the four large diodes which can be found on the underside of each amplifier board, under the big capacitors Try measuring across all four with an ohmmeter ­ if one has an internal short circuit, it should be quite obvious. Page11 Contents Copyright © 2000 Linn Products Limited. Paul O'Neill LK2 Service Manual Fuse blowing Constant Fuse blowing Constant Big capacitor(s) faulty ­ probably internally short circuit. Measure across both capacitors on the channel that is causing the fuse to blow ­ a faulty capacitor will measure short circuit or certainly low impedance. If in doubt, compare with good channel . See Introduction to Fault Finding section (accessible via Linfo Website - Product Information) for tips on how to isolate faulty board Fault inside LK2, e. g. short circuit or similar. Replace faulty capacitor Part details: 10000uF; +/- 20%; 64V; Electrolytic Capacitor (Linn part no: CAP 085) Same part can be used for any version of LK2 See Introduction to Fault Finding section (accessible via Linfo Website - Product Information) for tips on tracing the fault. Also see circuit diagrams. Page12 Contents Copyright © 2000 Linn Products Limited. Paul O'Neill LK2 Service Manual Amplifier problems ­ Fault Table No output Symptom No output from both channels No output from one channel Circumstances Possibly intermittent Applies only to LK260 & LK275 Probably constant May be intermittent Possible Cause(s) Unit not powering up correctly. One of the "Reliability Modification" components has failed Amp has tripped. Cure See `Power up problems' section above Carry out "LK2 Reliability Modifications" ­ procedure can be accessed via Linfo ­ Product Information. See `Trip Faults' section below. No output from one channel OR occasionally may affect both channels No output from one channel Applies only to LK280 Probably constant No output from one channel Applies only to LK275 & later versions of LK260. Probably constant Power transistor (the large transistors clamped to the heatsink) faulty. It is sometimes possible to measure these transistors using an ohmmeter to check if faulty (usually internal short-circuit across one or more of the junctions), but also there is the possibility that the transistor measures okay but is indeed faulty. It will sometimes be necessary to change them to confirm or rule out this fault. Power transistor (the large transistors clamped to the heatsink) faulty. It is sometimes possible to measure these transistors using an ohmmeter to check if faulty (usually internal short-circuit across one or more of the junctions), but also there is the possibility that the transistor measures okay but is indeed faulty. It will sometimes be necessary to change them to confirm or rule out this fault. Check / replace power transistor(s). Part details ­ Q23 & Q30 ­ 2SA1386; PNP; 160V; 15A; MT100 (Linn part no: TRAN 017) Q24 & Q34 ­ 2SC3519; NPN; 160V; 15A; MT100 (Linn part no: TRAN 018) Check / replace power transistor(s). Part details ­ Q20 & Q27 ­ 2SA1386; PNP; 160V; 15A; TO218 (Linn part no: TRAN 017) Q24 & Q31 ­ 2SC3519; NPN; 160V; 15A; MT100 (Linn part no: TRAN 018) Page13 Contents Copyright © 2000 Linn Products Limited. Paul O'Neill LK2 Service Manual No output from one channel Applies only to earlier versions of LK260 Probably constant No output from one channel May be intermittent Power transistor (the large transistors clamped to the heatsink) faulty. [. . . ] 5. Refit boards into tray ­ just do the reverse of the dismantling process described at the start of this document. Refit sleeve Test amp fully Page8 Paul O'Neill Copyright © 2000 Linn Products Limited. All rights reserved. Linn Parts List (Bill of Materials) for PCAS 003 Amplifier Board for LK2 (60) & LK275 Power Amps Please note that this list is provided for guidance only. Linn Products cannot guarantee the accuracy of the information contained in the list and will not be held responsible for any errors that occur as a result of its use. [. . . ]