Can KT77s be used in place of EL34 in any amp (Chupacabra)

HT fuse blew in my Chupacabra. Hoping it was just a valve and if it is I have some spare sets of EL34s to use for the time being. It will likely drive me to pull the trigger on some new tubes though and I have been wanting to try KT77s in my Helios.
So I am wondering if I would be able to try them in the Ceriatone Chupacabra as well? And then the more general question beyond that is can they can into any EL34 amp?

Yes

Pete, pretty sure they are a drop-in replacement. Might just need a little bit different bias.

Bias 'em up just like you would an EL34.

Drop in and rebais.

Just dropped a quad into a Splawn QR due to the same issue. Blown HT (Slo-Blo) fuse. Pulled the power tubes and one of them looked suspect with discoloration inside; had the glass cracked all the way around the base. I contacted Scott and he said they were a direct replacement for the EL34B that were in there. Biased up and they rip!

I got the Chupacabra back up and running. I don't see anything visibly wrong with any of the JJ E34Ls that were in it and they all do light up. Tested for a short and found none.
Decided to replace the fuse and put in a spare set of Ruby EL34s I had and it is working. I didn't have it up very loud and I'll need to run this thing a bunch to feel comfortable since I can't see for sure that one of the power tubes was the issue. I do have a few spare fuses now so maybe I will put them back in and see what happens.