Hi Klement,  The STB cable need not be connected if you're using the Amazon replacement. STB is a signal output from the controller chip towards the original power supply unit, without the latter there isn't any need to keep it connected. You may try disconnecting it to check if you'll regain the power off function.

Where is the Jubilee part?

Hi DrewKrew,   Yes, the symptoms point to a power supply that is about to give up completely. 

No Affiliation Klipsch Forte IV For Sale | Audiogon  

No Affiliation Pair Klipsch KPT-535/4 3 way "pro Jubilee"... For Sale | Audiogon

You're persuasive, Charlie.  Back in ancient times -- 60 years ago -- I built many a Heathkit and Dynakit.  I still have a shack full of ham radio items that I built from scratch only 5 years ago.  But I know my own limits now, and I never built or messed with a pile of parts that cost $14k.  Nope, while encouragement is always welcome, caution is the present policy for this old man.

Must have been a great store.  One of my favorite record shops ran a couple LaScalas.  My first real exposure to the larger Klipsch speakers.

Hello - I pop in every once in a while looking for ways to improve the sound of my system. My current system is comprised of Khorns with ALK extreme slope x-overs, Volti Mid Range horns with 4592-mid drivers, DE-10 tweeter drivers with CNC tweeter lenses. My Amp is a MA352 McIntosh fed by an RME ADI FS 2 DAC. Music is streamed via a mini PC 16 gig memory AMD Ryzen 7 3750H  with an external power supply. Basically a notebook processor with no keyboard or screen. Controlled by Remote desktop.   I had an in home Demo of a Western Electric 91 E 300B Tube amp. While it did sound slightly better I don't think it sounded $15,000 better, it was subtle maybe a bit warmer. Also demo'd was a Linn music streamer priced at $13,000. I could hear no difference between the streamer and the dac/pc that I currently have.   Tomorrow I am going to a shop to listen to a Furman power conditioner that sells for $2500. Since my house has a basement I can easily pull a 20 amp dedicated circuit for my system and swap out my speaker cables for a newer set. The cables I have are 25 years old and probably need a refresh. Will the 20 amp dedicated circuit make a difference versus the 15amp shared circuit?    Any thoughts?      Rick      

You mean my DHA2 crossovers suck? I really liked them. Josh is sending them back to me since he went active.

Hello - I pop in every once in a while looking for ways to improve the sound of my system. My current system is comprised of Khorns with ALK extreme slope x-overs, Volti Mid Range horns with 4592-mid drivers, DE-10 tweeter drivers with CNC tweeter lenses. My Amp is a MA352 McIntosh fed by an RME ADI FS 2 DAC. Music is streamed via a mini PC 16 gig memory AMD Ryzen 7 3750H  with an external power supply. Basically a notebook processor with no keyboard or screen. Controlled by Remote desktop.   I had an in home Demo of a Western Electric 91 E 300B Tube amp. While it did sound slightly better I don't think it sounded $15,000 better, it was subtle maybe a bit warmer. Also demo'd was a Linn music streamer priced at $13,000. I could hear no difference between the streamer and the dac/pc that I currently have.   Tomorrow I am going to a shop to listen to a Furman power conditioner that sells for $2500. Since my house has a basement I can easily pull a 20 amp dedicated circuit for my system and swap out my speaker cables for a newer set. The cables I have are 25 years old and probably need a refresh. Will the 20 amp dedicated circuit make a difference versus the 15amp shared circuit?    Any thoughts?      Rick