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Linn Lk280 one side very hot

nostromo

nostromo

pfm Member
I have 6 Lk280 amps for my active Isobarics. One of these is running very hot just on one side. It's heatsink fins are too hot to touch (almost cause a burn) whereas the other side is just warm to the touch. None of the other heatsinks are this hot.

This is with no music playing, just turned on and idling. It sounds OK when played though.

Any ideas of what may be causing this, I only recently noticed this but it may have been like this for a while. Any pointers to a possible fix will be much appreciated.

I'm concerned it's cooking the board and will cause it to fail soon.
 
Have the amps been recapped at some point?
"Too hot to touch" in idle is definitel a little bit too hot.

It might be a good idea to open the hot amp, and see if anything is obviously wrong. Follow the available service manual (via Google) for this. While you are at it you can make a recap at least of the smaller 100uf electrolytics and see if this cures the issue. Of course order the parts first...
 
Prevention is better than fault finding!!

Better to look now while it is still working and you can take some values and readings (IMO)
 
cubeasic said:
Have the amps been recapped at some point?
"Too hot to touch" in idle is definitel a little bit too hot.

It might be a good idea to open the hot amp, and see if anything is obviously wrong. Follow the available service manual (via Google) for this. While you are at it you can make a recap at least of the smaller 100uf electrolytics and see if this cures the issue. Of course order the parts first...
Click to expand...

Yes these were recapped by myself with Elna caps for the board and Mundorfs for the Power smoothng...in 2015 that's 6 years ago, using:

((MLGOAG-090) - 15000uF 63V Mundorf MLytic AG Electrolytic Capacitor)

((ELNAS-110) - 100uF 63V Elna Silmic II Electrolytic Capacitor)

Bought from Hifi Collective (I've just checked my order history with them).

I've had a look inside and there's nothing I can see that's obviously blown. These are Class A/B and I was wondering if this one has decided it be more A than B...;).
 
So the electrolytics should be fine.
Are the voltages before and after the regulator ok? Before around 60V, after around 40V.

There are also tant caps at several places that eventually could be replaced.
Maybe one of them shorted...
 
Mynamemynaim said:
Prevention is better than fault finding!!

Better to look now while it is still working and you can take some values and readings (IMO)
Click to expand...

I'm useless with electronics, I'm a complete novice (with a bad habit of rushing in to break things). I wouldn't know what to measure and where (I do have a multi-meter, mostly used for continuity testing-;)).

You might have seen in an earlier post from me ... I've ruined a Linn Activ Crossover. The crossover is now in pieces and being slowly repaired with help from Youtube...it's going well (IMHO, won't know for sure until I install it though).
 
cubeasic said:
So the electrolytics should be fine.
Are the voltages before and after the regulator ok? Before around 60V, after around 40V.

There are also tant caps at several places that eventually could be replaced.
Maybe one of them shorted...
Click to expand...

As a complete novice, I'm not sure where to find the regulators ( I'll hazard a guess these will be close to the two large capacitors?) I'll open it up again tomorrow and post a few photos so you may be able to point me at them?

The tants I've heard are a protection mechanism and these switch off the amp if it overheats or if it blows a speaker driver or there is no load connected.....I could be wrong here, it's just what I remember from reading stuff (disclaimer: to anyone like me who is a novice, I know nothing about these tants really). How would you suggest testing these? Does the amp have to be on and connected to speakers?

The tants are small round (yellow?) caps that look like little plastic balloons? Would you have a part number/source/specification?
 
nuit73 said:
Take a look here: https://pinkfishmedia.net/forum/threads/tweaking-recapping-an-lk280.28568/
Click to expand...
I just finished reading that thread and downloading the LK2 service manual. Will take a look at the service manual (bedtime reading).
There is mention in that thread that LK280 does get hot....but no mention of asymmetric temperatures. Lot's of talk of taking the PSU circuit out into a separate box with beefier components, much like a Linn Spark. As it happens I bought a Spark from ebay over 8 years ago, just for the hell of it, I've never used it, all I can remember is that it was bloody heavy, must be full of solid lead! If it ever got dropped, it would cause serious toe damage. I've made a mental note to open that up and have a look (out of curiosity) and perhaps when I retire to re-cap it and see if it does anything...probably best to try it on the mid amps....and then if it's good try and make a couple more 'knock-off' copies.
 
nostromo said:
As a complete novice, I'm not sure where to find the regulators ( I'll hazard a guess these will be close to the two large capacitors?) I'll open it up again tomorrow and post a few photos so you may be able to point me at them?

The tants I've heard are a protection mechanism and these switch off the amp if it overheats or if it blows a speaker driver or there is no load connected.....I could be wrong here, it's just what I remember from reading stuff (disclaimer: to anyone like me who is a novice, I know nothing about these tants really). How would you suggest testing these? Does the amp have to be on and connected to speakers?

The tants are small round (yellow?) caps that look like little plastic balloons? Would you have a part number/source/specification?
Click to expand...

I can take a photo and mark the relevant positions. This might take a few days though. You can consult the available service manual, there are part values in the appendix. I think only two different tant-types were used, 100 uf and 22 uf.
 
cubeasic said:
I can take a photo and mark the relevant positions. This might take a few days though. You can consult the available service manual, there are part values in the appendix. I think only two different tant-types were used, 100 uf and 22 uf.
Click to expand...

I'm busy with work this week, but hope to get time over the weekend to open it up and take some pictures to post here. I'd like to get a handle on this and fix as it may reoccur with my other LK280s in the future.
 
If it getting hot I would not connect it to any valuable loudspeakers until you know its not outputting anything orrible.
 
The speakers are active Linn Isobariks and very precious to me. The channel in question is driving one of the bass units and these are the most expensive and hardest to physically replace... So I'll heed your advice and use it on the tweeters, if and when I think it's safe to do so.

I've taken the photos... Will post tomorrow.
 
Good morning folks,

When I opened up this LK280 to remove the PCB for photographing, I noticed that the bolt that holds the output side of the board onto the heat sink was missing. I don't feel this could be the culprit as the main heatsink link is linked via the steel pad which uses thermal paste. I've now found the bolt and put everything back as I couldn't see anything obviously wrong. But of course if you do....please point it out for me. Also if there is anything I should be looking at replacing e.g. the tants, please point me to those too.

I've notice some heat burn on both under-sides of the board, more severe on the output side (Speaker connector side). The components however look fine to me.

Any advice gratefully received. Thank you for taking the time to have a look.

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I’d agree with blanket replacement of the tants and electrolytics , especially since those brown jobs are too big.

Id also (very carefully) remove and check the black rectangular polystyrenes, these are very susceptible to heat damage.
 
David, I have those big Elnas in all 6 amps, so I'm reluctant to change them all. The other amps are running fine, just warm to the touch. I don't know anything about the tants, are these the 'balloon' looking ones, especially on the bottom of the board and what spec are these, what's best to replace these with? The black rectangular ones (polystyrene?) there are about 15 of these all on the LHS of the board....that looks like a job too far for my capabilities but I'm mulling over whether to attempt that.
 
I like it where it says 'CLYDE BUILT!' with an exclamation mark. If this was a big ship, I'd better understand the emphasis...:)
 
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