Krell ksa 80 amp blowing circuit breaker when turned on

[pasquesd]

I have a vintage Krell KSA 80 that won't turn on.
It blows the 20 amp circuit breaker immediately when switching to on.
Does anybody know what the problem usually is when this happens?

Also, any idea of where I can download a wiring diagram for it?

Thanks, Bob

[harley .guy07]

I would say it would be in the power supply in the amp that is shorting out and making the 20 amp breaker blow but I do not know the internals of this amp well enough to say anything past that point but I would recommend getting in contact with krell and sending them an email just to see if they might have a archive of their schematics for this amp who knows they might just have the information that you need other than that I would recommend someone in your area that works of high end amps and knows Krells. You could also try a google search for a KSA 80 wiring diagram and see if anything comes up online that possibly someone has posted in the past.

[pasquesd]

Thanks for the feedback. Sounds like good advice. I read a couple threads that gave me the idea that Krell isn't too anxious to help out folks with older Krell equipment. I'm hoping they're wrong.
Thanks again.
Bob

[Mr Peabody]

Just curious if the amp is new to you or this is something that just started? Not sure why the amp would be doing that but 20 amps should be sufficient. I personally like the sound of those older Krell and the KSA Class A are nice.

[blackraven]

Have you looked under the hood of the amp? Take off the cover of the amp and see if anything is loose, burned or melted. You could also with great caution, turn on the amp and see if anything sparks, making sure that you do not get electrocuted. The other risk is doing more damage to the amp.

[pasquesd]

Have you looked under the hood of the amp? Take off the cover of the amp and see if anything is loose, burned or melted. You could also with great caution, turn on the amp and see if anything sparks, making sure that you do not get electrocuted. The other risk is doing more damage to the amp.

Hi, Yes I removed the top plate and looked all around for any signs of burnt circuitry, none found. I'll try looking for a spark as you suggested.

Thank you, Bob

[pasquesd]

Yes, the amp is new to me. Bought at an auction under the pretense that it worked. Foolish me. Won't believe that auctioneer again mind you. And to think that I'm an old customer of theirs.
The 20amp circuit is dedicated and has handled two Yamaha M80s in tandem prior to this.
Thanks, Bob

[Mr Peabody]

If you aren't familiar with the Krell you will be very pleased once you are able to get it to work. The KSA are Class A and still sought after, and hold their value pretty well.

I remember some older Krell had a "recall" where owners had to replace the fuses with a different value, these were provided by Krell. I know it was several KAV models but can't remember if KSA. It may be worth checking the rail fuses to see if a prior owner did something stupid to bypass a fuse.

[pasquesd]

If you aren't familiar with the Krell you will be very pleased once you are able to get it to work. The KSA are Class A and still sought after, and hold their value pretty well.

I remember some older Krell had a "recall" where owners had to replace the fuses with a different value, these were provided by Krell. I know it was several KAV models but can't remember if KSA. It may be worth checking the rail fuses to see if a prior owner did something stupid to bypass a fuse.

Hi, thanks for the info. I'll definately check on the fuse recall and also the possibility of the bypass issue.

Thanks, Bob

[HD67]

Bob,

you solve your problem yet?
Had exactly the same effect. Inrush into the capacitors is so massive the fuse will react as if short-circuited.
Magneto automatic fuses will not withstand this abuse, unless replaced with 16A slow version or heavy duty 25A version (as opposed to 16A regular). Note: 25A is allowed only in switched mains (i.e. washing machines), not plugged appliances as wall sockets are only approved for 16A.
You can fool these magneto's by switching the amp on (thus blowing the fuse), then reset the fuse (a couple of times) until it holds. Sparks will fly! but no worries. Switching will need to coincide with the middle of the 55Hz sinus to avoid blowing the fuse, sort of Russian roulette.
If your fusebox is equipped with classic porcelain fuses you can also use the "slow" 16A version.
I replaced my magneto automatic with a similar design cylindrical fuse holder that will fit the same rail, using 40A (don't tell anyone) glass insert fuse from an auto-parts seller. These are used for off-the-wall car stereo's working on 12V, so they need a lot of Amps.
I'm not sure what the rules of conduct are regarding advertising, but check out Siemens cylindrical fuse holder?

Regards
Egbert

ps: funny thing is: the cylindrical fuse holder actually sounds better than the magneto automatic! Wider soundstage. I was reaching for the curtains as the sound seemed to bounce off the side window...

pps: the fact that fuses blow suggests you own a specimen that was produced before soft-start relais were added to these beasts. Which is good, because without a relais in the mains circuit they reportedly sound better.

[pasquesd]

Bob,

you solve your problem yet?
Had exactly the same effect. Inrush into the capacitors is so massive the fuse will react as if short-circuited.
Magneto automatic fuses will not withstand this abuse, unless replaced with 16A slow version or heavy duty 25A version (as opposed to 16A regular). Note: 25A is allowed only in switched mains (i.e. washing machines), not plugged appliances as wall sockets are only approved for 16A.
You can fool these magneto's by switching the amp on (thus blowing the fuse), then reset the fuse (a couple of times) until it holds. Sparks will fly! but no worries. Switching will need to coincide with the middle of the 55Hz sinus to avoid blowing the fuse, sort of Russian roulette.
If your fusebox is equipped with classic porcelain fuses you can also use the "slow" 16A version.
I replaced my magneto automatic with a similar design cylindrical fuse holder that will fit the same rail, using 40A (don't tell anyone) glass insert fuse from an auto-parts seller. These are used for off-the-wall car stereo's working on 12V, so they need a lot of Amps.
I'm not sure what the rules of conduct are regarding advertising, but check out Siemens cylindrical fuse holder?

Regards
Egbert

ps: funny thing is: the cylindrical fuse holder actually sounds better than the magneto automatic! Wider soundstage. I was reaching for the curtains as the sound seemed to bounce off the side window...

pps: the fact that fuses blow suggests you own a specimen that was produced before soft-start relais were added to these beasts. Which is good, because without a relais in the mains circuit they reportedly sound better.

Hi!

Thank you for sharing your experience and solutions to your problem. It certainly makes sense to me and worth trying. I'm hoping my problem doesn't result in purchasing a new transformer, as that would be a big expense to deal with.

Bob

[blackraven]

If you are getting an inrush current that is causing the problem then maybe you need a voltage regulator-

Search Results:

Line-R 1200VA Automatic Voltage Regulator

[HD67]

Hi Bob,

why would you need a new transformer? All you need to do is tame your fusebox. To us here in Europe that would be a 100,- Euros for the breaker and some change for a fuse. That's a paltry sum compared to what we spend on gear, right?

As far as needing new stuff is concerned: lift the lid off the amp, make some good detailed pictures of the stuff inside and send them to a real coinaisseur (pun intended).
These class-A babies tend to run high and hot, and need a recap every once in a 15 years or so. If postponed too long one or more will go "pop" and then you're in real mess. Besides, they used plastic bolts to fasten some stuff in there and these tend to go brittle. A typical open-up, re-cap, re-bolt & calibrate job will take some 4 hours of skilled labour and parts (regular stuff, nothing expensive; maybe output relais, cinch, some small bits and pieces while you're at it), so you can work out the cost for a local job.

regards
Egbert

[HD67]

This is what it could look like;

rail-type breaker box


and
replacement breaker

[pasquesd]

Thank you for the advice. That sounds like a good possibility. I'll check around and see if I can find a voltage regulator to try it with.

Bob