tweaking classic Linn LK1 & LK2 / LK280

A friend of me have issues with his LK2. The input voltage (measured to GND) from the regulated power supply rises up to nearly +110V at the positive rail and fall down to -10V at the negative rail.
Which error is most likely ?
Schema you will find by post #51 (last pdf, see below)
under
http://www.diyaudio.com/forums/solid-state/106226-tweaking-classic-linn-lk1-lk2-lk280-6.html
Q30 and Q34 already replace, without success.
Maybe one of the other user's observe the same behaviour and have find out the reason therefore.
Thank you for comments.
 
A friend of me have issues with his LK2. The input voltage (measured to GND) from the regulated power supply rises up to nearly +110V at the positive rail and fall down to -10V at the negative rail.
Which error is most likely ?
Schema you will find by post #51 (last pdf, see below)
under
http://www.diyaudio.com/forums/solid-state/106226-tweaking-classic-linn-lk1-lk2-lk280-6.html
Q30 and Q34 already replace, without success.
Maybe one of the other user's observe the same behaviour and have find out the reason therefore.
Thank you for comments.
Issue fixed. Very rare occured unwanted internal disconnecting between the GND transformer winding and the outside cable coming from transformer winding going to the outside secondary winding connector.
Thus transformer's GND-reference isn't available from outside and I need therefore a replacement. Maybe there are user's, which had make an upgrade to a SPARK and can make me an offer from such a no longer used toroidal transformer. Please avoid PM and send an information concerning this to my own email address
kirschner-hifiQweb_de
(please replace "Q" and "_" by the right signs).
thank you very much in advance.
 
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Issue fixed. Very rare occured unwanted internal disconnecting between the GND transformer winding and the outside cable coming from transformer winding going to the outside secondary winding connector.
Thus transformer's GND-reference isn't available from outside and I need therefore a replacement. Maybe there are user's, which had make an upgrade to a SPARK and can make me an offer from such a no longer used toroidal transformer. Please avoid PM and send an information concerning this to my own email address
kirschner-hifiQweb_de
(please replace "Q" and "_" by the right signs).
thank you very much in advance.
I open the transformer and note an interrupt between the winding wires for GND and the flexible cable, that goes outside. The reason was oxidation (maybe by aging of cable insulation - this I have never seen before). After resolder and replace the cable, that goes outside, transformer works correct. But as consequence, the power amp was damaged (one half get two times voltage for a too long time) and I need new power devices TIP35C/TIP36C or BD249C/BD250C in the old TI-outline as show in follow image:
http://img.jofogas.hu/images/BD249_..._tranzisztor_par_es_BD250a_16996423836274.jpg
currently available power transistors from this type unfortunately only available in this (newer) outlines:
http://img.alibaba.com/img/pb/616/376/774/774376616_416.jpg
http://i.ebayimg.com/images/a/(KGrHqEOKisE4nfCWvWBBOLSPQiKNg~~/s-l300.jpg
This means, that I have to widen the opening in the power amp PCB for the larger outline design by milling. This I want to avoid and therefore the question: where I can order the mentioned transistors in the old TI outline?
Thank you for advices.
 
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For best success I would suggest to place your question here:

Parts - diyAudio
I have found 10 pcs from each type on ebay thanks to a reference from a member. But the repair prozedure proved to still be quite complicated.
After replace the two pairs BD249/250 and all transistors and regulators LM317/LM337 in the regulator circuit I note no voltage difference in the positive rail between input and output of the regulator (61V5 both at input and output). After hard search I found the reason: shorted Diode D14 near by regulator U1 - go to last pdf-file, last page from post #51 under
http://www.diyaudio.com/forums/solid-state/106226-tweaking-classic-linn-lk1-lk2-lk280-6.html
After replace I note an offset at the loudspeaker output from approximately 2V5. The reason therefore was a burned R4 (150 ohms) and shorted tantal electrolytics C2 and C20 (NFB) - go to the same pdf, but first page.
After replace this parts the LK2 works fine, even after a long period of listen.
 
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I have found 10 pcs from each type on ebay thanks to a reference from a member. But the repair procedure proved to still be quite complicated.
After replace the two pairs BD249/250 and all transistors and regulators LM317/LM337 in the regulator circuit I note no voltage difference in the positive rail between input and output of the regulator (61V5 both at input and output). After hard search I found the reason: shorted Diode D14 near by regulator U1 - go to last pdf-file, last page from post #51 under
http://www.diyaudio.com/forums/solid-state/106226-tweaking-classic-linn-lk1-lk2-lk280-6.html
After replace I note an offset at the loudspeaker output from approximately 2V5. The reason therefore was a burned R4 (150 ohms) and shorted tantal electrolytics C2 and C20 (NFB) - go to the same pdf, but first page.
After replace this parts the LK2 works fine, even after a long period of listen.
By chance I have at the same time a LK2-80 with serial number 209572. The reason for checking was the fact, that only a low idle current was noted, both at the output and VAS-stage. Therefore the large and the small heatsink remains cold. After hard search again I found the reason: Tantal ellektrolytic C8 (VAS-stage) was soldered in the wrong polarity, possibly already while the manufacturing - go to pdf-file No 6, first page from post #51 under
http://www.diyaudio.com/forums/solid-state/106226-tweaking-classic-linn-lk1-lk2-lk280-6.html
Because wrong polarity at this capacitor occurs an unwanted leakage current through a virtual parallel resistance. This prevented the current flow in the VAS-stage.
After replace this cap the power amp device works correct and the idle current value is now about 150 mA, exact same value like the second channel.
Amazingly for me was the fact, that this capacitor working in reverse mode was not defective.
It would be interesting for me to know how many devices of LK280 arround the mentioned serial number have been installed incorrectly this capacitor - thanks for advices.
 
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I open the transformer and note an interrupt between the winding wires for GND and the flexible cable, that goes outside. The reason was oxidation (maybe by aging of cable insulation - this I have never seen before).
Here the pics therefore
the yellow/black colored wire was replaced by the blue wire.
 

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The Linn dealer in our 'burb told me that if you ran the amp without a load it would fail. I happened across one at a thrift shop -- one bad channel and top cover missing.

Not one to just do the recommended modifications -- i have a bunch of Thermal-Trak transistors and LME49811 and this PCB almost ready for burning:
 

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Realizing of a very large Heatsink for Linn's LK-1 Voltage Regulator Transistors

In genuine condition there are three small heatsinks and consequently burned PCB area arround this. For me the best solution to avoid this are the approach from Linn's modell KAIRN and KARIK - go to the first two images below.
In order to realize the LK-1 in retrospect, many steps are necessary - go to the additional images.
 

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Continuation Picture Series

more images
 

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Continuation Picture Series

last images.

Not only the voltage regulator transistors, but some components in the moving coil head amp goes also very hot - there is to observe also a burned PCB arround the parts of this unit. Each channel has two 150R resistors, which are to be soldered at a great distance from the printed circuit board - go to image No 5 and 6.
But what can I do for cooling the ZTX653/753 ?
Maybe using of the FZT653/753 (SMD outline) with the possibility to solder on a small copper heat sink ? - go to
https://ae01.alicdn.com/kf/HTB1UADS...-font-FZT653TA-FZT653TC-SOT223-Transistor.jpg

Unfortunately the approach from Linn's model KAIRN (see images No 7, 8 and 9) is with LK-1 not to realize without performing a new PCB design.
 

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Hi

from yours photos i see, in 317 3D circuit, the resistor normally called R1 is connected to IC input pin .

Have You checked if the regulator output is stable changing input voltage ?
Yes (go to image number 7, post#72 - the right-hand wire of the 120R resistor must connectet of the output (middle) PIN from LM317).
And a second mistake was present while photo shooting:
The GND-connection between the upper end of the LM317 parts and the mainboard (near by the main capacitors) was missing (go to image number 3+4, post#73).
But both errors were eliminated before performing the operating test procedure.
Nevertheless - thank you very much for this advice.
 
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LK2/LK2-80 Capacitors for it's Power Supply - which should I prefer

I am looking for capacitors in a special size: 40x55mm (10mF/63V 0r 4,7mF/100V)

This I have found:

1) KEMET ALT22A472DD100 (formerly BHC-Aerovox - ESR unknown)
ALT22A472DD100 | KEMET Aluminium Electrolytic Capacitor 4700μF 100V dc 40mm Can - Solder Tag, Radial ALT22 Series +85degC | KEMET
ALT22A472DD100 KEMET | Mouser Deutschland
http://www.filcap.de/wp-content/uploads/Datenblatt-Serie-ALP22-und-ALT22_23-85°C.pdf
2) ftcap SIH Series 47210040050 (34mΩ) or 10306340050 (29mΩ)
http://www.ftcap.de/fileadmin/user_...trolyt_kondensatoren/webboxen/Snap_in/SIH.pdf
3) ftcap SIG Series 10306340050 (14 mΩ)
http://www.ftcap.de/fileadmin/user_...trolyt_kondensatoren/webboxen/Snap_in/SIG.pdf
4) 4d-electronic
https://www.reichelt.de/Becher-Elkos/BE-4-700-100/3/index.html?ACTION=3&GROUPID=3146&ARTICLE=5396
from http://www.4d-electronic.de/
(please note: wrong image)

unfortunately the versions under
http://www.exxelia.com/en/product/detail/71/felsic-hv
which have from my own view the best capacitors for audio
don't provide the wanted sizes.

Maybe one of the members can give me advices - thank you very much.
 
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I'd strongly recommend to do these mods to any owner of a LK2/60:

- do the Reliability Mods (R33 und R49 > 2 W, C6 & C19, see below)
- heatsinks for Q10, Q11 und Q14 (the still get hot)
- evtl. heatsinks for LM317/337
- add the two 100 µF, the LK2/75 comes with
- renew several lytics, e.g. Pana FC, Silmic or Nichicon Muse
- consider to renew the big lytics, go for 10.000 µF
- if you remove the transformers and put them in an external case, you'd gain spce for additional capacitance
- swap C5, C6 & C19 for Micas
- decrease C1 to 2.2 nF, C2/20 > 330 µF + MKP (e.g. 150 nF)

Hope I didn't miss anything.



Does it sound better?

It does. :D


The modded LK260 play more authoritively, quicker and more dynamicly. The
former "british Sounding" has gone. If you like the old british day, don't do it.
If you like music and realism - do it !!
Probably there are more modifcations you could do, but there's already more
air and a deeper basement. I can listen to Marcus Millers Bass lines better.

I have to say I already have put the transformers into an external case
(similar to "Spark").
Hard to understand why Linn chose C1 so big and C2/20 that small. I cannot
understand als why there are no heatsinks on Q10/11/14. Even with some
Copper HS they still are 55° - 60° C hot. No wonder the melt the styrenes.
R49 also still gets hot. This one is prone to burn as it's just two 1/4 W types
from factory.
Follow mods for good reliability are very importend by the old LK2 versions with PCAS003 board:
1) R49: 2K2, 5W (VAS stage, was in the first version 2K2, 0,125W, later 2x1K1, 0,125W)
2) R50+R11: 8K2, 5W (for reference current through zeners D1/D5, was in the first version 2x3K3, 0,125W, later 2x4K3, 0,125W)
3) Q10/11/14 from VAS stage on the exist main heatsink (very difficult steps necessary, but possible - go to the attached images; please note: this is not possible on the LK2-80 PCB's "PCAS020")
4) replace burned C6 (68p) and C19 (220p)
5) R33 (20K, 0,125W) replace by 2x10K, 3W
Now the main heatsink for the output power and serial voltage regulator devices will be more hot. But now no longer burned parts on the PCB.
But a question: how can I adjust the idle current through the output transistors ?
 

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Now the Linn forum's gone, these tweaks and updates here become far more important.
I'm a bit confused though, as many posts are for the original Lk2 power amp (with some LK1 preamp tweaks thrown in).
If anyone is still glancing in here, what about the LK280 and maybe Klout, the circuits of which seem different to the LK2-60 and 75 versions? I ask because the Klout always sounded 'better' than the 280 yet has a similar circuit I gather - a stock 280 sounds a bit 'forced' to me in comparison. is most of this in the reservoir supply size, or are there circuit tweaks which would free off a 280 sonically, more like the Klout? I've been offered a working 280 for silly cheap money and would like to investigate it after thirty years away.
 
I am looking for capacitors in a special size: 40x55mm (10mF/63V 0r 4,7mF/100V)

This I have found:

1) KEMET ALT22A472DD100 (formerly BHC-Aerovox - ESR unknown)
ALT22A472DD100 | KEMET Aluminium Electrolytic Capacitor 4700μF 100V dc 40mm Can - Solder Tag, Radial ALT22 Series +85degC | KEMET
ALT22A472DD100 KEMET | Mouser Deutschland
http://www.filcap.de/wp-content/uploads/Datenblatt-Serie-ALP22-und-ALT22_23-85°C.pdf
2) ftcap SIH Series 47210040050 (34mΩ) or 10306340050 (29mΩ)
http://www.ftcap.de/fileadmin/user_...trolyt_kondensatoren/webboxen/Snap_in/SIH.pdf
3) ftcap SIG Series 10306340050 (14 mΩ)
http://www.ftcap.de/fileadmin/user_...trolyt_kondensatoren/webboxen/Snap_in/SIG.pdf
4) 4d-electronic
https://www.reichelt.de/Becher-Elkos/BE-4-700-100/3/index.html?ACTION=3&GROUPID=3146&ARTICLE=5396
from http://www.4d-electronic.de/
(please note: wrong image)

unfortunately the versions under
http://www.exxelia.com/en/product/detail/71/felsic-hv
which have from my own view the best capacitors for audio
don't provide the wanted sizes.

Maybe one of the members can give me advices - thank you very much.
any news ?