Linn-LK2-pwr-sm维修电路原理图.pdf
Copyright 2000 Linn Products Limited. All rights reserved. Paul ONeill Service Manual for LK2 Series of Power AmpsService Manual for LK2 Series of Power Amps Covering LK2(60), LK275 also - since the LK2 can emit a considerable amount of heat and has a fairly strong electrical field, it is better to keep it away from other devices that may be adversely affected by this. Avoid locations that have high humidity or the chance of the unit getting wet. Avoid locations where there is a lot of dust. Handling Emitter Collector; Bass Collector) of every transistor on the faulty board. In general a working junction will measure many Kohms or even Megohms, whereas a faulty junction will tend to measure almost short circuit perhaps a few ohms possibly up to 500ohms at most. If in doubt, compare with the same junction on the good channel and replace transistor if you suspect faulty. It is advised that you check every single transistor on the board, i.e. dont stop if you find a faulty one, as quite often there is more than one faulty transistor on the board. Remember to include the big transistors (the 4 that are clamped to the heatsink) when measuring. The above test, while not absolutely guaranteed to find every faulty transistor, will find the vast majority. Remember that it is quite common for more than one component to be faulty, as often a faulty component will cause damage to others around it in the circuit. See below for advice on how to check for this. Other components Other components are slightly less straightforward. The same principles as with Transistors above can be applied (measure using an ohmmeter) but there is a lot more work involved and a lesser chance of success as these parts are less likely to go faulty and less likely to follow such a straightforward pattern as the transistors. If you have a fault that is not caused by any of the faults listed in this manual i.e. the fault tables and this section - then try to narrow the fault down to an area of the circuitry using conventional fault-finding and then measure and/or replace the components in that area. Resistors can of course be easily measured for impedance but are very unlikely to go faulty unless another component failure has damaged them, so look for telltale signs like scorching etc on or around the resistor that might indicate this. The Capacitors on this circuit can also be checked using an ohmmeter as above. Sometimes capacitors will internally short-circuit so worth a quick measurement. Check the components (as transistors above) using an ohmmeter. RadioFans.CN 收音机爱 好者资料库 LK2 Service Manual Page10 Copyright 2000 Linn Products Limited. All rights reserved. ContentsPaul ONeill Power-up problems Fault Table Wont power up SymptomCircumstancesPossible Cause(s)Cure Wont power up. Power LED dead may be broken or may have a bad connection Reconnect cable or repair if broken. One channel dead May be intermittentChannel has “tripped”See Trip Faults section below One channel dead May be intermittentBoard is faultySee Amplifier Faults section below Wont switch off Amp will not switch off using power switch May be intermittentFaulty power switchReplace power switch use Linn part no: SWRL 006 RadioFans.CN 收音机爱 好者资料库 LK2 Service Manual Page11 Copyright 2000 Linn Products Limited. All rights reserved. ContentsPaul ONeill Fuse blowing SymptomCircumstancesPossible Cause(s)Cure Fuse blowingMay be intermittentWrong type of fuse fittedReplace fuse(s) with correct value +/- 20%; 64V; Electrolytic Capacitor (Linn part no: CAP 085) Same part can be used for any version of LK2 Fuse blowingConstantFault inside LK2, e.g. short circuit or similar. See Introduction to Fault Finding section (accessible via Linfo Website - Product Information) for tips on tracing the fault. Also see circuit diagrams. RadioFans.CN 收音机爱 好者资料库 LK2 Service Manual Page13 Copyright 2000 Linn Products Limited. All rights reserved. ContentsPaul ONeill Amplifier problems Fault Table No output SymptomCircumstancesPossible Cause(s)Cure No output from both channels Possibly intermittent Unit not powering up correctly. See Power up problems section above No output from one channel Applies only to LK260 PNP; 160V; 15A; MT100 (Linn part no: TRAN 017) Q24 NPN; 160V; 15A; MT100 (Linn part no: TRAN 018) No output from one channel Applies only to LK275 PNP; 160V; 15A; TO218 (Linn part no: TRAN 017) Q24 NPN; 160V; 15A; MT100 (Linn part no: TRAN 018) RadioFans.CN 收音机爱 好者资料库 LK2 Service Manual Page14 Copyright 2000 Linn Products Limited. All rights reserved. ContentsPaul ONeill No output from one channel Applies only to earlier 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. Check / replace power transistor(s). Parts may be as listed in the box above or they may be as listed below, depending on whether it is an earlier or later version of LK260. Part details Q20 PNP; 100V; 25A; TO218 (Linn part no: TRAN 005) Q24 NPN; 160V; 15A; TO218 (Linn part no: TRAN 004) No output from one channel May be intermittentRegulator U1 or U2 faultyReplace faulty regulator part details: U1 LM317T Voltage regulator (Linn part no: IC 005) U2 LM337T Voltage regulator (Linn part no: IC 006) No output from one channel Applies to LK280 only May be intermittent or may be constant U3 (hybrid card) faulty. U3 is the small board that is connected at 90degrees to the main board beside the big caps. Replace U3 Linn part number IC 030 (not available elsewhere). Take great care when removing U3 from the board as it is very easy to rip tracks. The pins in the middle are especially difficult to de-solder use heat 10%; 2.5W; 100V. (Linn part no: RES 050). No output from one channel May be intermittentFaulty component in circuit.See “Fault Finding on the LK2 hints PNP; 160V; 15A; MT100 (Linn part no: TRAN 017) Q24 NPN; 160V; 15A; MT100 (Linn part no: TRAN 018) TrippingMay be intermittentRegulator U1 or U2 faultyReplace faulty regulator part details: U1 LM317T Voltage regulator (Linn part no: IC 005) U2 LM337T Voltage regulator (Linn part no: IC 006) TrippingApplies to LK280 only May be intermittent or may be constant U3 (hybrid card) faulty. U3 is the small board that is connected at 90degrees to the main board beside the big caps. Replace U3 Linn part number IC 030 (not available elsewhere). It is also worth checking / replacing regulators U1 10%; 2.5W; 100V. (Linn part no: RES 050) RadioFans.CN 收音机爱 好者资料库 LK2 Service Manual Page16 Copyright 2000 Linn Products Limited. All rights reserved. ContentsPaul ONeill TrippingApplies only to LK280 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. Check / replace power transistor(s). Part details Q23 PNP; 160V; 15A; MT100 (Linn part no: TRAN 017) Q24 NPN; 160V; 15A; MT100 (Linn part no: TRAN 018) TrippingApplies only to LK275 PNP; 160V; 15A; TO218 (Linn part no: TRAN 017) Q24 NPN; 160V; 15A; MT100 (Linn part no: TRAN 018) TrippingApplies only to earlier 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. Check / replace power transistor(s). Parts may be as listed in the box above or they may be as listed below, depending on whether it is an earlier or later version of LK260. Part details Q20 PNP; 100V; 25A; TO218 (Linn part no: TRAN 005) Q24 NPN; 160V; 15A; TO218 (Linn part no: TRAN 004) TrippingMay be intermittentFaulty component in circuit.See “Fault Finding on the LK2 hints & tips” section at the beginning of this manual. Distortion / crackling etc SymptomCircumstancesPossible Cause(s)Cure Output distorted may one or both channels May be intermittentPower-up problem if amp receives insufficient power it will struggle to amplify the signal and distortion will occur See Power-up problems section above. RadioFans.CN 收音机爱 好者资料库 LK2 Service Manual Page17 Copyright 2000 Linn Products Limited. All rights reserved. ContentsPaul ONeill Output very badly distorted Applies only to LK260 & LK275 Probably constant One of the “Reliability Modification” components has failed Carry out “LK2 Reliability Modifications” procedure can be accessed via Linfo Product Information. Distorted outputMay be intermittentFaulty component in circuit.See “Fault Finding on the LK2 hints & tips” section at the beginning of this manual. Crackling noise from output Probably intermittent may be temperature dependent Transistor in circuit faulty junction is breaking down See “Introduction to Fault Finding” (accessible via Linfo Product Information) Or See “Fault Finding on the LK2 hints & tips” section at the beginning of this manual. DC at output SymptomCircumstancesPossible Cause(s)Cure DC voltage at output. Fault symptoms vary levels of voltage etc. Probably constantRegulator U1 or U2 faultyReplace faulty regulator part details: U1 LM317T Voltage regulator (Linn part no: IC 005) U2 LM337T Voltage regulator (Linn part no: IC 006) DC at outputMay be intermittentFaulty component in circuit.See “Fault Finding on the LK2 hints & tips” section at the beginning of this manual. RadioFans.CN 收音机爱 好者资料库 Paul ONeill Copyright 2000 Linn Products Limited. All rights reserved. LK2(60) & LK275 Reliability ModificationsLK2(60) & LK275 Reliability Modifications Some components on the PCAS 003 (used in the LK260 & LK275) are sometimes prone to failure after many years of use. This modification can be carried out as a preventative measure to prolong the life of the amplifier or as a combined repair / prevention if one of the components has failed. Carrying out this modification will repair around 60 70% of LK2 faults Important Information about this modification Please read through this procedure in its entirety before starting any work. It is important to follow ALL instructions carefully and exactly This procedure involves soldering and de-soldering and it is advised that only personnel with a fairly high degree of soldering skill undertake this task. Due to the age and the years of heat stress some of the solder joints may have changed their chemical properties and if this is the case it will be quite difficult to melt them. Use flux (or melt new solder onto the old solder joint), Use heat and patience - not force. The changes outlined in this procedure will protect the LK2 from similar potential failures in the future by using higher wattage resistors than were originally used and adjusting the position of some components to minimise heat damage It is advised that all these modifications are carried out to both channels. Estimated time for completion of this task: 1 hour CAUTION Important Safety Information Residual Voltage. With certain faults especially but also under normal circumstances, there can be residual voltage stored in the boards which could cause quite a serious electric shock. To avoid this, it is best to leave the LK2 switched off for a few hours before starting work on it and then using a voltmeter, measure across the metal contacts of each of the big capacitors (DO NOT TOUCH) on each channel (DC voltage). If there is a voltage remaining on these capacitors then it is important to discharge it either short across the + & - contacts with a screwdriver this can cause a harmless but spectacular and terrifying bang combined with a huge spark. It is much more pleasant to connect one of the resistors that you will use for the mod the 2.4Kohm/2.5Watt and connect this across the contacts of the capacitors until the voltage has discharged. The LK2 is very heavy and has sharp fins on the heatsink be very careful when lifting, handling, dismantling and re-assembling not to injure yourself. RadioFans.CN 收音机爱 好者资料库 LK2 Reliability Modifications Page2 Copyright 2000 Linn Products Limited. All rights reserved. Paul ONeill Fault Symptoms There are several different symptoms, depending on what component has failed (symptoms usually affect one channel only): No output at all Bad distortion at output DC at output Units affected Potentially all LK260s or LK275s (those not upgraded to LK280) Equipment Required (Those items marked may not definitely be required) Workbench clear of debris and clutter No2 Posidriv (Supadriv) Screwdriver No1 Posidriv (Supadriv) Screwdriver 2.5mm Hex key or Allen Key Medium sized flat-blade screwdriver 7mm spanner or nut-runner 5.5mm spanner or nut-runner Soldering Iron, temperature controlled 25 watt with fine tip Solder Sucker Fine solder Paper handkerchiefs or paper towels Heatsink compound (a white grease-like substance that improves heat conduction) Fine Pliers Soft cloth Parts Required 20Kohm, 2.5Watt resistorQty 2 (per unit) 2.4Kohm, 2.5Watt resistor Qty 2 (per unit) 220pF 160V Polystyrene capacitorQty 2 (per unit) 68pF 160V Polystyrene capacitorQty 2 (per unit) Note if you cannot find the above parts available in your local area, some alternatives are available in the case of the resistor wattage values: It is possible to use a higher wattage resistor in each case, although it tends to be the case that the higher the wattage, the larger the resistor and it may not be able to physically fit in the space available or may touch against another device or component, especially in the case of R33 (not a good idea). It is possible to use a slightly lower wattage resistor in each case, however if too low. this will shorten the life of the resistor and the fault may re-occur. A minimum of 1 watt is recommended. RadioFans.CN 收音机爱 好者资料库 LK2 Reliability Modifications Page3
