Replacement for KSA-50

It is one of the 10 best amplifiers ever made and certainly the best Krell ever manufactured. I don't own Krell products as I have very well regarded tube amplifiers. However I am familiar with this amplifier.
Send it back to Krell and they will bring it up to new status and will also replace some worn passive parts on both channels and you will have an amplifier good for another 20 to 25 years

Yes, the Krell is great amp, but... those Theils wouldn't mind some more power, and FWIW, I never much cared for fans on amps.

I agree that sending the unit to Krell is probably the way to go. I noticed an ad for Krell MDA 500s that mentioned servicing by a company in Bridgeport, CT called The Service Department, a possible alternative, though I don't have any experience with them. Do check to make sure you haven't just blown a fuse, though.

While Unsound is probably right based on his longer experience with the 3.5s, I'll note that I did use a Krell KSA 50 Mk II for my Thiel CS3s for a while (till I sold them to get Duntechs) and in my moderate sized room (20 by 18 feet) it drove the Thiels with no strain. It's a lot more powerful than its power rating would imply.

By the way, I (and I think most of people who posted) am assuming that you are talking about the original KSA 50, and not the later KSA 50s. Is that assumprion correct?

Thanks Grannyring for your suggestion! It was a fuse. I have replaced it and it is working now.

While we are talking about my set up, I have another question. I have removed the equalizer that comes with the Theil 3.5 speakers as per a suggestion in Stereophile . Sound is cleaner now, but lacks bass weight below 60Hz or so. Question to all of you is what subwoofer do you recommend to go with this speaker to add some bass weight to the music.

Thanks for all your suggestions and help,

I think your better off using the eq. The eq starts boosting at 70 Hz, not an area where most sub-woofers do their best work. If you want to use a sub, I suggest using the 40 Hz setting on the eq. I don't think the eq really causes that much compromise, and the benefits far outweigh any disadvantages (which might have more to do with preconceived prejudice?). You can insert the eq into a tape loop of your pre, if you'd like to switch it out when listening to music without any sub 70 Hz sounds, but then you'll be introducing more things into the signal path.