2. tech-talk
  3. 191946-197971

Issue with Krell KSA-250

Hello-

It's been a minute since I've been on the forums here, but I'm glad they are still around!

I am the second owner of a Krell KSA-250 amplifier. For the past 10 years it hasn't given me any problems. Then today, when I turned it on, it emitted a rather loud buzzing sound. This wasn't coming from the speakers (like a ground loop hum), this was a very startling almost "mechanical" buzz sound. The buzz does not stop until I turn the unit off.

I'm not sure where to start. I called my local audio repair store, but they don't work on Krell. They suggested I contact Krell, which is my next step, but seeing as I'd have to freight this for it to be repaired, I'm hoping someone here might shed some light on what's happening. I've made a short 15-second video of the issue, but I don't think I can upload it here. I'm happy to provide it though.

Any thoughts you might have would be appreciated.

Thanks,

Blake

blakeh
Post removed 
jea48
4,425 posts
 

@invalid , Ya lots out there on the Net about problems with the Krell KSA-250 amp. Almost think the layout guy that designed the placement of components built in a self destruct feature.

You’ve probably already watched this video. (Krell KSA-250 recapping). The heat from those power resistors cause a lot of damage to everything that is near them. Including the soft start circuit board. Note the two relays. My gut tells me that is causing the buzzing sound.

Good chance, high probability, the electrolytic caps need replaced. Not sure I would spent a lot of money on the old amp.

 

DIY Audio, Krell KSA repair

.

gs5556
1,234 posts
 

What I would first start to look for:

Check for DC at the wall outlet. Check if the transformer cover can be moved by hand, if so then look at the bolts holding down the cover. Remove the cover and see if the rubber or elastomer bushing is still intact.

That is a 60hz buzz so it’s an AC issue, and it’s either the transformer or the soft start relay coil (those are the only two ac inductors I can think of). If it’s the transformer, then it’s probably the bridge rectifier has an open diode and only 60 hz is getting to the secondary instead of 120hz. If it’s the relay, then its probably a shorted rectifier diode, sending ac instead of dc to the coil and causing the contacts to chatter.

sqitis
56 posts
 

OP, very common issue with this series of amps. My buddy had the kinda rare KSA-250s and he had it repaired for the same issue like 3-4 times in a 10yr period. You could look at George Meyer but they may be backed up as well - https://www.georgemeyer-av.com/

blakeh OP
5 posts
 

Thanks for all the advice! I ended up taking it into Stereo Rehab in Chicago and the experience could not have been better! Casper obviously knows what he's talking about. Turns out it is a front relay. No problems with the caps or transformer. He took me through the whole unit, explained what was happening and gave me a reasonable estimate to fix it (cheaper than I thought it would be). Just an all around great experience. I should have it back in about four weeks.

Thanks,

Blake

More to discover