Craig B
Re:trophile
An old friend just dropped off his LK1 and 2 x LK275 which have been in storage for many years now. These had been used to passively bi-amp Nexus LS-250 'speakers since new. He remembered there having been some distortion on one channel for some time before they went into storage.
I have had the LK1 in before, suffering from the none-responsive front panel keypad issue. Fortunately, the pre-amp is one of the earlier examples with the voltage adjustment pot on the control board. This has been working fine since having had a twiddle with it to find the magic spot where both the keypad and IR remote work.
As the LK275s hadn't been switched on for a very long time, I gave them a 'softish' start via a connected in series lightbulb and tested for DC offset. After 10 minutes, one amp was showing 38.2V on the right channel (note V not mV!). The left channel was at .053V. Within 30 minutes, the left channel heatsink was getting warm to the touch whereas the high DC right channel heatsink was still cold.
I haven't had the cover off for a visual inspection yet, however, we've already exceeded my very limited level of expertise wrt testing for amplifier faults, plus the individual amplifier boards are reportedly a bugger to work on, with through-board components being as tightly packed as sardines.
On a possibly related note, my research has turned up Linfomation concerning 'LK2 Reliability Modifications' that were to have been performed on all LK2(60)/LK275 amplifiers. There are references to bending a tant away from a hot resistor and replacing a couple of resistors that tended to overheat, one of which is buried beneath one of the large PS caps. I am certain that none of these mods have been carried out on these two amps.
I've included a link to the service manual which includes the reliability modifications for anyone who is interested in having a look.
Any and all suggestions gratefully received.
http://www.acousticpsychos.com/Files/Linn-LK2-pwr-sm.pdf
I have had the LK1 in before, suffering from the none-responsive front panel keypad issue. Fortunately, the pre-amp is one of the earlier examples with the voltage adjustment pot on the control board. This has been working fine since having had a twiddle with it to find the magic spot where both the keypad and IR remote work.
As the LK275s hadn't been switched on for a very long time, I gave them a 'softish' start via a connected in series lightbulb and tested for DC offset. After 10 minutes, one amp was showing 38.2V on the right channel (note V not mV!). The left channel was at .053V. Within 30 minutes, the left channel heatsink was getting warm to the touch whereas the high DC right channel heatsink was still cold.
I haven't had the cover off for a visual inspection yet, however, we've already exceeded my very limited level of expertise wrt testing for amplifier faults, plus the individual amplifier boards are reportedly a bugger to work on, with through-board components being as tightly packed as sardines.
On a possibly related note, my research has turned up Linfomation concerning 'LK2 Reliability Modifications' that were to have been performed on all LK2(60)/LK275 amplifiers. There are references to bending a tant away from a hot resistor and replacing a couple of resistors that tended to overheat, one of which is buried beneath one of the large PS caps. I am certain that none of these mods have been carried out on these two amps.
I've included a link to the service manual which includes the reliability modifications for anyone who is interested in having a look.
Any and all suggestions gratefully received.
http://www.acousticpsychos.com/Files/Linn-LK2-pwr-sm.pdf
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