I made all the aluminum components for this amp in New Hampshire USA at a company called AAVID Thermalloy. You wouldnt believe the care that goes into making the base and heatsinks. The are handled with white cotton gloves after machining.
Thanks for sharing the parts list. Most people would not do that. I had a KSA - 150 and that amp ROCKED. Krell Pre-amps SUCKED, and I went to the SP9 or higher preamp to match it. Damn that sounded amazing. Thanks from the advice from Andy Singer from NYC.
holy crap, nice job, i was worried at first when I started watching because I did not know if you really knew what you were into! I bought a KSA 300s recently that had service done and these amps are amazing (and great space heaters as well!) Now enjoy listening!
superb recap and off course all the whole job. On second hand sites, peoples also say with an old but at the time expensive unit,that a good-looking outside that it's in perfect condition.Not that 20 years is old, but it's revision time, which ain't cheap...but well done
I just got done rebuilding a KSA-150 that flamed out before I got it. The soft start board got so roasted that I would really like to replace it, if I could find a clean condition spare board. My KMA-160 monoblocks were actually easier to work on and don't have the heat problems the KSA-150/250 have.
@nicklytras Well... Then use Sprague and Mallory for normal purpose use. Sprague in driver and output boards and Mallory in the softstart. I prefer using better quality caps when i restore electronics. Sprague is not a bad capacitor at all, but a modern design cap as Panasonic FC is well known to be a good choice for audio applications. My unit still sounds like a KRELL !
Very nice Amp and an excellent video and jobb fragglan !!! It's nice to see a video which is informative and well done, I would very much like to hear the sound of this monster !!! Keep up the good work and enjoy your Krell :-)
@ethorii I've heard of people sent there amplifier several times to krell for repair , and the part that failed are just the softstart board and the overheated resistors who kill everything around them. Very bad layout for the resistors. This problem is solved in my case.
@Menningerproperties Yes, it was many hours of work. But if you do it your self, you now every part is changed and you can spend endless time to resolder bad joints. I found more than twenty of them, and one joint that was forgotten! A little bit of loosy quality check i suppose. I think this amp will stay in my home for a long time. And to listen to it brings you to heaven !
I have two KSA 80. Also had the 300s, and 100s. My buddy wants me to sell the KSA80 and step up to the newer FPB series. No way. If in fact heat is the big issue discussed here, and i get an amp thats nearly unused, then there are no roasted parts, the caps are still young enough to be viable, and updates can be performed before things roast. I know nothing of repairs, but that seems a fairly oblivious way to go about it. Kudos to the OP for this, and showing me a weak spot as i consider buying a KSA 250
charles - take your friends advice and sell the 80. I had an 80 and traded up to the KSA250, into my Apogee Stage, and what a difference - massive improvement, in every area. I regret selling the 250 8 years ago, and would like another, or at least a 150, to drive my Maggie 1.7i's.
Superb effort! Real nice and informative movie. I had model Second Series Rowland 7's that burned their inrushcurrent resistors but there were no other components around them luckily.
nice work, I am just starting a service on a KSA 150 and unfortunately some under qualified tech been in it already changing components and wrecking the copper traces where they clearly do not know how to desolder on dual sided boards. would be great to have the service info on this!
Hi, do you know where I can find the bias voltages and procedures for this amplifier? I have one also with a burnt soft start board that I am recapping/restoring
Hi I looked at some pictures when i installed the main caps, and what i can see i didn't need any shims. For sure i haven't changed anything from original layout. Regards// Fragglan
Hi fragglan. I need your experties. My Rel Storm III has two 10,000uf-80vlt-85º caps, i want to upgrade to larger values...12,000uf-100vlt-105º(or 15,000uf), what caps (brand) would you recommend ? Mundorf, as far as i know, does not make 12k or 15k 100vlt-105º !!! The R8 resistor fryed... it is a 10k-1w-5%... it's the Storm's weekness, i will use a 15k-3w-5% resistor instead, i read about it. But... what i really want to know is what caps (brand) you recommend me under these values ? Thank you, in advance. Oh... snap-in caps on the pcb... i could use the screw ones, that's easy to attach. Ricardo Barradas
What reason would you have for putting in larger capacitors? That doesn't make the amp sound any better but it does increase startup inrush current which stresses the inrush current limiting resistors more, resulting in them failing more quickly, just as happened to this KSA-250. Don't think that bigger parts are necessarily better. Often they're NOT.
My Crown DC-300A is from 1978 and is still running all it's original components, without any problems. Even the DC offset is still totally in spec. So recapping such a young amp is futile unless there is an actual fault or there is a known issue with some particular components, particularly as caps from the Krells era were much better than the ones form the Crown.
Not quite that simple. I doubt that the design would allow caps to be exposed to any abnormal heat, so that wouldn't be an issue. As I mentioned, modern caps are hugely more reliable than older types. The caps exposed to most stress in any amp, more so in a class A design, are the power supply reservoir caps. I would imagine Krell would use high quality types in this location, they will have a long life, even with such use. They can easily be tested for signs of degradation or failure, so do not need to be just replaced on a notional time basis. Modern high quality signal path components are extremely reliable and rarely fail. Electronics aren't like cars, they don't require routine servicing to prevent excessive wear or used up filters etc.
+turboslag Obviously you don't have any idea about Krell.Krell is class A amp.Crown is not.Krell runs way much hotter than Crown.There is absolutely no comparison among those two.Are you a tech or you just shooting s---t?
it also depends on how hard the amplifier has been run. This amplifier will run at 320 watts per channel at 8 ohms, the krell units are very under rated. if you see some poor capacitors it is advisable to replace them all. Also remember that the krell and crown amplifiers are in a whole different leauge. when this amplifier was new it would have cost about the same as a small car. Small defects to this amplifier will cause sound quality to deminish. i would assume that this amplifier would drive equally as fine loudspeakers which are very sensitive compared to professional loudspeakers. Remember. This amplifier has to sound good at low volumes too, an amplifier that has sad or old components on the inside will make it hum more and just overall sound worse. Over time the ESR of the capacitors increases also, which is not good. So for an unsensitive PA amp, not replacing caps is fine. but for a sensitive amp with sensitive speakers... its more critical. but yes. i am the kind of person that will just replace the bad caps!! i cant be bothered pulling an entire amp down!!
You just don't know. YES, the KSA-150 and KSA-250 and the closely related MDA-300 and MDA-500, and all other Krell amps of the same vintage, really DO need to be recapped, at least by the time they're 20, because they're notorious for driving capacitors to failure and when they fail things get UGLY. These amps are carrying enormous energy in them, beside which your DC-300A is a toy, and so when they have a problem there's plenty of stored power that will make a small problem a bigger one. The caps don't just fail, they are likely to fail and BURN HOLES THROUGH THE PC BOARDS. Note that the caps on the soft start board were toast. The KSA-150 I rebuilt was MORE toasty than this one in this video. It's a different story when the amp is storing THOUSANDS of joules of energy and something goes wrong.
@@smallenginedude71 It doesn't really depend how hard it's been run, as class A amps run FLAT OUT even when not driving speakers, just idling. In fact, the harder you drive them, the COOLER they run. When idling, ALL the generated power is going straight to the heatsinks. It's not like class A/B where it runs cool at idle and heats up when driving speakers, it's the exact opposite.
Good job. Like you, I can't believe it powered up with so many toasted caps & res. Would you mind telling me who recorded that beautiful soundtrack played in the background?? Reminds me of some of the Windham Hill series....
maybe a bit late, but that brown "safe cap" that was cracked from the heat in the softstart board, what are the values on that one? mine is also broken, and i cant figureout how many pf or nf it is, do you remember what yo swithed it out for? best wishes.
The capacitors are fried because there is a huge resistor almost touching them that gets to be hundreds of degrees. Stupid ass design. I had a KSA-150 that had the same resistor on the front board. They could have easily lifted it up and away from the other circuit parts to preserve them.
Beautiful and informative video. Looks easy but not sure how to tough to dissemble and put it back. My KSA250 did not start after not use for half year. Some chattering sound from the front right relay, then the unit tripped after several seconds. Any clue? I like to repair this myself instead sending it back to Krell. Too much trouble and expensive. Anyone has a front soft start board circuit in hand, please let me know. Thank you for your help in advance.
Why would such a highly prized mega expensive power amp have such problems?? I have two 20 year old 250 watt NAD power amps and they work like they were bought yesterday and still sound breathtaking. I bought both for less than £800 new back then. The Krell cost silly money by comparison.
I gave a good answer to that question a few comments above. In short, when your amps are storing THOUSANDS of joules of energy, they'll do terrible things to capacitors that are starting to go bad, though those same caps might have years left if they were installed in an amplifier with less energy storage. High power systems are always more demanding of component qualities.
@@Sirflatch Wasn't the 300S one of the first to use plateau biasing? They were supposed to be nowhere near as good as the previous series, the ones here.
Where are you located? Do you do repairs? Can you repair my unit ? How do I get in touch with you ? I have a Krell Class A unit Please let me know thank you
Electrical Engineer.....hmmmm. No he is onley a electronic nerd who work as a Cable Guy at the saw mill.. And he just love to pull the cables... PS...Fragglan I'm just kidding.
superb recap and off course all the whole job. On second hand sites, peoples also say with an old but at the time expensive unit,that a good-looking outside that it's in perfect condition.Not that 20 years is old, but it's revision time, which ain't cheap...but well done
I made all the aluminum components for this amp in New Hampshire USA at a company called AAVID Thermalloy. You wouldnt believe the care that goes into making the base and heatsinks. The are handled with white cotton gloves after machining.
Very cool. I’m not far from the factory! Then and now…
Nice.
Thanks for sharing the parts list. Most people would not do that. I had a KSA - 150 and that amp ROCKED. Krell Pre-amps SUCKED, and I went to the SP9 or higher preamp to match it. Damn that sounded amazing. Thanks from the advice from Andy Singer from NYC.
holy crap, nice job, i was worried at first when I started watching because I did not know if you really knew what you were into! I bought a KSA 300s recently that had service done and these amps are amazing (and great space heaters as well!) Now enjoy listening!
The song is : Blue Angel
The artist are : Adam Drake, Nell Williams, Alison Pearse
superb recap and off course all the whole job. On second hand sites, peoples also say with an old but at the time expensive unit,that a good-looking outside that it's in perfect condition.Not that 20 years is old, but it's revision time, which ain't cheap...but well done
I just got done rebuilding a KSA-150 that flamed out before I got it. The soft start board got so roasted that I would really like to replace it, if I could find a clean condition spare board. My KMA-160 monoblocks were actually easier to work on and don't have the heat problems the KSA-150/250 have.
@nicklytras Well... Then use Sprague and Mallory for normal purpose use. Sprague in driver and output boards and Mallory in the softstart. I prefer using better quality caps when i restore electronics. Sprague is not a bad capacitor at all, but a modern design cap as Panasonic FC is well known to be a good choice for audio applications. My unit still sounds like a KRELL !
Very nice Amp and an excellent video and jobb fragglan !!! It's nice to see a video which is informative and well done, I would very much like to hear the sound of this monster !!!
Keep up the good work and enjoy your Krell :-)
@ethorii I've heard of people sent there amplifier several times to krell for repair , and the part that failed are just the softstart board and the overheated resistors who kill everything around them. Very bad layout for the resistors. This problem is solved in my case.
@Menningerproperties Yes, it was many hours of work. But if you do it your self, you now every part is changed and you can spend endless time to resolder bad joints. I found more than twenty of them, and one joint that was forgotten! A little bit of loosy quality check i suppose. I think this amp will stay in my home for a long time. And to listen to it brings you to heaven !
I have two KSA 80. Also had the 300s, and 100s. My buddy wants me to sell the KSA80 and step up to the newer FPB series. No way.
If in fact heat is the big issue discussed here, and i get an amp thats nearly unused, then there are no roasted parts, the caps are still young enough to be viable, and updates can be performed before things roast. I know nothing of repairs, but that seems a fairly oblivious way to go about it. Kudos to the OP for this, and showing me a weak spot as i consider buying a KSA 250
charles - take your friends advice and sell the 80. I had an 80 and traded up to the KSA250, into my Apogee Stage, and what a difference - massive improvement, in every area. I regret selling the 250 8 years ago, and would like another, or at least a 150, to drive my Maggie 1.7i's.
Superb effort! Real nice and informative movie.
I had model Second Series Rowland 7's that burned their inrushcurrent resistors but there were no other components around them luckily.
nice work, I am just starting a service on a KSA 150 and unfortunately some under qualified tech been in it already changing components and wrecking the copper traces where they clearly do not know how to desolder on dual sided boards. would be great to have the service info on this!
Hi, do you know where I can find the bias voltages and procedures for this amplifier? I have one also with a burnt soft start board that I am recapping/restoring
@jRedTree85 Hi, electrical engineer.. not really. I work as an Industrial Electrician. But i have some knowledge about electronics as well.
Hi I looked at some pictures when i installed the main caps, and what i can see i didn't need any shims. For sure i haven't changed anything from original layout.
Regards// Fragglan
Hi fragglan. I need your experties. My Rel Storm III has two 10,000uf-80vlt-85º caps, i want to upgrade to larger values...12,000uf-100vlt-105º(or 15,000uf), what caps (brand) would you recommend ? Mundorf, as far as i know, does not make 12k or 15k 100vlt-105º !!! The R8 resistor fryed... it is a 10k-1w-5%... it's the Storm's weekness, i will use a 15k-3w-5% resistor instead, i read about it. But... what i really want to know is what caps (brand) you recommend me under these values ? Thank you, in advance. Oh... snap-in caps on the pcb... i could use the screw ones, that's easy to attach. Ricardo Barradas
What reason would you have for putting in larger capacitors? That doesn't make the amp sound any better but it does increase startup inrush current which stresses the inrush current limiting resistors more, resulting in them failing more quickly, just as happened to this KSA-250. Don't think that bigger parts are necessarily better. Often they're NOT.
My Crown DC-300A is from 1978 and is still running all it's original components, without any problems. Even the DC offset is still totally in spec. So recapping such a young amp is futile unless there is an actual fault or there is a known issue with some particular components, particularly as caps from the Krells era were much better than the ones form the Crown.
Not quite that simple. I doubt that the design would allow caps to be exposed to any abnormal heat, so that wouldn't be an issue.
As I mentioned, modern caps are hugely more reliable than older types. The caps exposed to most stress in any amp, more so in a class A design, are the power supply reservoir caps. I would imagine Krell would use high quality types in this location, they will have a long life, even with such use. They can easily be tested for signs of degradation or failure, so do not need to be just replaced on a notional time basis. Modern high quality signal path components are extremely reliable and rarely fail.
Electronics aren't like cars, they don't require routine servicing to prevent excessive wear or used up filters etc.
+turboslag Obviously you don't have any idea about Krell.Krell is class A amp.Crown is not.Krell runs way much hotter than Crown.There is absolutely no comparison among those two.Are you a tech or you just shooting s---t?
it also depends on how hard the amplifier has been run. This amplifier will run at 320 watts per channel at 8 ohms, the krell units are very under rated. if you see some poor capacitors it is advisable to replace them all. Also remember that the krell and crown amplifiers are in a whole different leauge. when this amplifier was new it would have cost about the same as a small car. Small defects to this amplifier will cause sound quality to deminish. i would assume that this amplifier would drive equally as fine loudspeakers which are very sensitive compared to professional loudspeakers. Remember. This amplifier has to sound good at low volumes too, an amplifier that has sad or old components on the inside will make it hum more and just overall sound worse. Over time the ESR of the capacitors increases also, which is not good. So for an unsensitive PA amp, not replacing caps is fine. but for a sensitive amp with sensitive speakers... its more critical. but yes. i am the kind of person that will just replace the bad caps!! i cant be bothered pulling an entire amp down!!
You just don't know. YES, the KSA-150 and KSA-250 and the closely related MDA-300 and MDA-500, and all other Krell amps of the same vintage, really DO need to be recapped, at least by the time they're 20, because they're notorious for driving capacitors to failure and when they fail things get UGLY. These amps are carrying enormous energy in them, beside which your DC-300A is a toy, and so when they have a problem there's plenty of stored power that will make a small problem a bigger one. The caps don't just fail, they are likely to fail and BURN HOLES THROUGH THE PC BOARDS. Note that the caps on the soft start board were toast. The KSA-150 I rebuilt was MORE toasty than this one in this video. It's a different story when the amp is storing THOUSANDS of joules of energy and something goes wrong.
@@smallenginedude71 It doesn't really depend how hard it's been run, as class A amps run FLAT OUT even when not driving speakers, just idling. In fact, the harder you drive them, the COOLER they run. When idling, ALL the generated power is going straight to the heatsinks. It's not like class A/B where it runs cool at idle and heats up when driving speakers, it's the exact opposite.
Damn that's nice amp now!
Good job. Like you, I can't believe it powered up with so many toasted caps & res. Would you mind telling me who recorded that beautiful soundtrack played in the background?? Reminds me of some of the Windham Hill series....
Krell really needed to fire their layout engineers.
why werent they high quality?
The power transistor is MJ-15024 & MJ-15025？
Just got a ksa200 in great shape. Did you replace all the caps? If no, besides visual check how did you determine which ones to replace?
maybe a bit late, but that brown "safe cap" that was cracked from the heat in the softstart board, what are the values on that one?
mine is also broken, and i cant figureout how many pf or nf it is, do you remember what yo swithed it out for? best wishes.
@SlayerSalamanda . It's a audio swap from youtube... i don't remember the title. sorry.
Are those silicone pads also known as the 'gaskets'?
I need to buy a part of circuit because my KSA 250 is a single ended. Do you have one used or new one?
Вот вам и Крелл,столько упущений и конструктивных просчётов !!!
The capacitors are fried because there is a huge resistor almost touching them that gets to be hundreds of degrees. Stupid ass design. I had a KSA-150 that had the same resistor on the front board. They could have easily lifted it up and away from the other circuit parts to preserve them.
Beautiful and informative video. Looks easy but not sure how to tough to dissemble and put it back.
My KSA250 did not start after not use for half year. Some chattering sound from the front right relay, then the unit tripped after several seconds. Any clue? I like to repair this myself instead sending it back to Krell. Too much trouble and expensive.
Anyone has a front soft start board circuit in hand, please let me know. Thank you for your help in advance.
Bravo!
Why would such a highly prized mega expensive power amp have such problems??
I have two 20 year old 250 watt NAD power amps and they work like they were bought yesterday and still sound breathtaking. I bought both for less than £800 new back then. The Krell cost silly money by comparison.
I gave a good answer to that question a few comments above. In short, when your amps are storing THOUSANDS of joules of energy, they'll do terrible things to capacitors that are starting to go bad, though those same caps might have years left if they were installed in an amplifier with less energy storage. High power systems are always more demanding of component qualities.
Your 20 year old NAD amps sound breathtaking? You have never heard reference grade electronics, then.
What is this music ?
Hands up idol
Wish I cd do this stuff. The reason I dodnt buy the ML amp I wanted.. if anything went wrong, the inside looked so damn complicated
I love my KSA-250
I love mine too!!! I just got the KSA3OOS !!!! :O)
@@Sirflatch Wasn't the 300S one of the first to use plateau biasing? They were supposed to be nowhere near as good as the previous series, the ones here.
Amazing!
Where are you located? Do you do repairs? Can you repair my unit ? How do I get in touch with you ? I have a Krell Class A unit Please let me know
thank you
@stuffeengvall Hmmmmm... You'lll eat this on monday :)
구할수 있을까요?
For sale?
Electrical Engineer.....hmmmm.
No he is onley a electronic nerd who work as a Cable Guy at the saw mill..
And he just love to pull the cables...
PS...Fragglan I'm just kidding.
changed just after 20 years!,for this overpriced load of crap i'd want them to last 60 years.
thats the ugliest chair I've ever seen..
Shame on such a high end brand to last that short . Shameful and so un professional
Krell is well known for this kind of flops. Fortunately not all high quality audio gear is like that
Such waste of good parts on these amps...
Atelieurul29 - I presume the 29 in your name is your age in Months! What a moronic thing to say.
@@davybloggs1564 keep presuming that if this is what makes you feel better! Still... Why so salty?
superb recap and off course all the whole job. On second hand sites, peoples also say with an old but at the time expensive unit,that a good-looking outside that it's in perfect condition.Not that 20 years is old, but it's revision time, which ain't cheap...but well done