Blowing Fuses. Dennis Had Inspire 300B SET

@moose89 , I’ll relate another problem I once encountered with my Cary amp and how I fixed it:

I’d turn the amp on and on one side the bias would run away high regardless of where the bias pot was set (not a self-biasing amp). I emailed Cary about it (this was the new Cary, not the Dennis Had Cary), and when they did get back to me, which was none too quick, they basically quoted me their shop rate and advised me to send them the amp. It’s an 80 lb. amp and I could not find the original box so I wasn’t crazy about that idea.

On another audio site I posted a thread (similar to what you have done) and a very patient DIY member who was quite generous with his time got back with me and together we troubleshot my amp and I fixed it.

So what he suggested I do, and what I believe you could do, is put it on a work table and remove the bottom panel (assuming that is where you would gain access). Then with a multimeter, using various settings (ohms for resistors and the capacitor setting for caps) check everything left and right and see if the readings are the same or if they are wildly different.

In my application, one of the signal caps measured way different than the other 3 using the capacitor setting of the mm. The member who was "talking" me through this suggested I buy a cap checker on Amazon that I could verify my buggy reading with the cap in the circuit. I did, and the reading continued to be bad so I bought all four new signal caps and that fixed my amp.

Since a capacitor related to the rectifier tube was previously mentioned, and I was once blowing 3A SB AC power fuses left and righton start up  that I am about 99.9% sure was related to one or more power capacitors, you could start by checking those against each other.

However, if you do decide to take this approach, either make or buy a shunt so you can be sure that all your caps are discharged before you get started.

@moose89 -- I would contact Dennis directly with your issue. You can contact Mr. Had at w4usr@att.net or radiom_dr2856nho@members.ebay.com. I have a Dennis Had Inspire 45 Amp and LP3.1 Preamp, and Mr. Had has answered numerous questions for me, usually responding within 24 to 48 hours. He is a very nice guy and is responsive to fans of his gear. My gear was made in 2018 (he signs and dates each piece of gear on the bottom with usually a gold or silver sharpie. I live in Winston-Salem, NC, which is about 80 miles from where Mr. Had lives.

A friend of mine has one of Mr. Had's 300B amps paired with a pair of Klipsch Cornwalls.  One of the sweetest sounding combinations I've ever heard.  I am looking at adding one to my collection, but my next purchase is going to be a tube Phono Preamp that Mr. Had builds every now and then.  I have Klipsch Forte's matched with my Inspire 45 (that's another story -- like an idiot I had the 45 hooked up to Polk Audio Monitor 10's before I moved my Forte's; 2 watts a channel into 89 efficiency speakers was NOT SMART!).  

Turn on the amp without the tubes installed. If the fuse blows send the amp in for repair. If not, then there's a 99% chance it's a bad tube.

A Dim Bulb Tester can save you some fuses.

I am in New Jersey if you need assistance.