This time it's a Klout (where do they think these names up?!)
As you can see from the photo, the left channel is just showing a red LED, and has no output.
First off remove the top...We're going to need to remove the left hand amplifier board to inspect and repair...
... which takes a lot of disassembly!Disconnect the transformer, and the remote switching board. Unscrew the single screw securing remote input socket from the baseplate (you can leave it attached to the rear panel). You can now remove the baseplate, remote switching board and transformer.
Unscrew the input socket for the board we want to remove from the rear panel, and remove the two long cap screws that secure the output sockets. The cap screws are located in between the heatsink fins. There are 6 more cap screws securing the output transistors heatsink block, and the board itself to the heatsink. Remove these. You can now wiggle the offending board from the chassis.
Cursory checks on the board show all 4 output transistors to have failed leaky. A sanity check with the good channel confirms this.
There are two pairs in parallel. Two 2SC3519's and two 2SC1386's. Thankfully these are still available at the time of writing, so are duly ordered up. Driver transistors Q20, Q21, Q22, Q30, Q31, Q27, Q26 and Q25 check OK
The ESR of the electrolytics are checked. There are six 100uF 63V caps, two 220uF 16V on each board. They read OK'ish, but not great, so are replaced. The main smoothing caps all read sub 0.01 Ohm, and are not replaced.
The small sub-board has two 68uF 16v caps on the top. They read almost open circuit! Replaced.
Once this channel is repaired, I'll re-cap the other as it won't be far behind failing!
The transistors are held to a heat spreader by these two nuts. Removal is fairly straight forward. Clean all the old, dried up heatsink compound form the spreader with some IPA.
Heatsink compound is cleaned off the heatsink, and a smear of new compound applied.
And the board squeezed back in place!
I reassemble the amp, just to test the freshly repaired channel before re-capping the good one.
It's good news.
All boxed up, tested and good for another 20 years :)
Hi Doz, I have the exact same issue with my Linn Klout. Do you do repairs?
ReplyDeleteSee "not a business" on the right hand side. Thanks.
ReplyDeleteI’ve re-capped / upgraded nine Klouts so far. All the small caps were off with those showing extreme heat stress (browning) being very off. Some of the small ones on the piggyback boards also dead. All small caps replaced with 105 degC rated for longer life. The large reservoir caps replaced with low ESR long life Vishays with 12,000 hr at 85degC. The earlier boards have a 4 pin layout so these were replaced like for like with new ones from Kemet. Where appropriate I added factory mods that were introduced through the Klouts life to the earlier ones missing those mods, according to serial nr. Key amongst these for sound improvement are: Mica shims under the output transistors, star washers under the transformer bolts and baseplate screws and a 47 nf Poly cap on the back of the board across the joints with the transformer wires. Adding snap on Ferrite rings onto the transformer wires to the main boards eliminates an annoying buzz on startup affecting some units, so its good to add those too. I’ve also had to replace broken phono sockets and an LED or two and replace two power switching boards with factory NOS, but those are no longer available. If you blow the remote on/off by using an non Linn Kairn amp which may be sending the wrong voltage / power, check diode D3 on the small power board just next to the big cap. Some units may get problems with the 12V relays
ReplyDelete