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KRELL KST-100 power issue

A

andruzo69

New Member
Hi everyone

Got a used Krell KST-100 a few days ago that was playing fine when I listened to it before I bought it.

I connected it today to a digital DAC with premplifier output.

I turned the Krell on. Played for about 10 minutes. Then the home circuit breaker went off.

When I reset the breaker and tried to turn on the Krell it makes a "charging sound" and then a second later the power switch turns off.

I took the top cover off and tried again and I noticed some smoke coming from underneath that seems to be from the front.

Here's a video I took of this:


I uncovered the bottom also to inspect.

As a first step to debugging this: I don't see any burnt traces on the top or the bottom, no burnt wires, no (visibly) problematic caps. Transformer *looks* ok, no visible signs of damage.

If I connect the amp to a power bar and try to power it up, it trips the power bar protection before the main switch of the krell shuts off.

I just can't see how connecting it and powering it up would have caused this. Is it age failure? Is it a faulty switch? Dead output transistors?

Some guidance from anyone would be appreciate as to where to start. I've included some pics.
 

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I think I would be talking to the seller about a refund. As is I know but that’s just to coincidental. If he has any integrity he/she would refund your money…. I would
 
The info I found on-line said the unit has a circuit breaker built in to the power switch among other protection:

www.manualslib.com

Protection Circuitry - Krell Industries Power Amplifier KST100 Owner's Reference Manual [Page 9]

Krell Industries Power Amplifier KST100 Manual Online: Protection Circuitry. There are no fuses in the KST-100. The amplifier is protected by a series of non-intrusive, opto-c_o, upled circuits that constantly evaluate the amplifier s operation. Appropriate protective action exists for...
www.manualslib.com www.manualslib.com

That the breaker in you home opened up and not the breaker in the unit suggest big problems.
 
You are correct, the on / off switch on a Krell is actually a circuit breaker. Just replaced one at the tune of $300.
 
TomD62 said:
You are correct, the on / off switch on a Krell is actually a circuit breaker. Just replaced one at the tune of $300.
Click to expand...
What would cause the power switch circuit breaker to shut off? Does that breaker goes off when the protective circuit engages? Or is that switch only for voltage supply issues?
 
^^^^ This. Get it to someone who knows what they are looking at before you turn it into an expensive door stop. Returning it would be my first choice.
 
just a guess but the power supply caps may have given up the ghost. Krells, ML and others who run the caps pretty hard are known for this.
 
andruzo69 said:
Roger that.

Just want to understand what could be the issue. Nothing wrong with that is there?
Click to expand...

No, nothing wrong with that at all.

But the advice to stop powering it up is also valid. Didn't the unit trip a breaker in your house?

The link for the manual has some decent information on the protection built in including the power switch/circuit breaker. It acts like any other circuit breaker and opens up when a certain threshold of current is hit.
 
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