LK2 Service Manual
Page15
Copyright © 2000 Linn Products Limited. All rights reserved.
Contents
Paul O'Neill
Trip (protection) problems
Important information about the Trip / Protection circuitry
About ‘Trip’
The LK2 series had a trip circuit for each channel, which was designed to protect the LK2 board and/or
speakers from a potentially damaging “over-current” situation. This means that if the LK2 senses that it is
drawing too much current, it shuts down the affected channel. This situation may be caused by a faulty
speaker (internal short circuit), speaker cables shorted together, very loud music, faulty pre-amp etc.
How to clear trip
Once a channel trips, it will remain in ‘trip-mode’ until the LK2 is switched off for up to 20 minutes. It is best to
ensure that you leave the unit switched off for the full 20 minutes – if you power it up before it has fully
discharged / un-tripped, the trip capacitors will charge up again and you will have to wait another full 20
minutes. We have heard of customers who do not leave it switched off for long enough, switching it on
before it is ready and perhaps doing this a few times then think the product has a permanent fault.
Continuous or repeated tripping
It is important to remember that the trip circuitry is included as protection and the LK2 may be tripping for a
very good reason. If tripping occurs continuously or even occasionally, it may be because the LK2 is doing
its job correctly and something within the system is causing it to trip. The source of the problem needs to be
isolated and removed (perhaps the speaker or the speaker cable, the pre-amp is faulty etc). See
Introduction to Fault Finding
for tips on how to trace (accessible via Linfo – Product Information).
It is, of course also possible that the LK2 is faulty, in which case, see table below.
Symptom
Circumstances
Possible Cause(s)
Cure
Tripping
May be intermittent
Power transistor (the large
transistors clamped to the
heatsink) faulty.
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)
Tripping
May be intermittent
Regulator U1 or U2 faulty
Replace faulty regulator – part
details:
U1 – LM317T Voltage regulator
(Linn part no: IC 005)
U2 – LM337T Voltage regulator
(Linn part no: IC 006)
Tripping
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).
It is also worth checking /
replacing regulators U1 & U2
(part details above) and the big
resistors at either side – R37 &
R46 – part details: 0.1ohm; 10%;
2.5W; 100V. (Linn part no: RES
050)
Содержание LK260
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