Hey Andrea! I figured it out! Turns out the problem was staring me right in the face! It was my power transformer My PT has the following taps. Ive build a number of 2xEL34 amps all based on the marshall 2204 power/rectifier platform. So when I sourced this PT, I thought nothing of grabbing a PT with 350v secondaries - especially one that would give me the 14v I need for the switching....because I always use PTs with 350v secondaries for these amps. So I just wired it up without realizing your schematic and layout was designed for a PT with 180V secondaries and a voltage doubling circuit in the rectifier (which is similar to what's going on in the 2203 power section - an amp Ive never built). The HV secondary center tap going in between the two 100uf capacitors was doubling the voltage on the B+ rail. C34/C35 held up, because I think the fact that they were tied in series increased their power handling...but the very next filter cap in line was C32....and thats why it exploded....and thats why fuses were popping when I had tubes in the amp. So I pulled the center tap from in-between C34/C35 and temporarily tied it to ground....and as soon as I did that, voltages on C34/C35 went right down to 485v!!!! So I did a little rewiring of the rectifier circuit....I went to a 4 diode center tap rectifier like in the 2204, I soldered the HV center tap to ground and I bridged the positive sides of C34 & C35 to use single 100uf 500v filter cap in C34 (my actual Friedman BE50 has a single 100uf in this location). The amp immediately came to life. After my usual start up testing, I put in the good tubes I had planned for this amp - and Im happy to report that it sounds just like my actual BE50. I'll post some pics in a new thread in the other section. But I wanted to thank you for your help and guidance throughout this entire process. Even though I had this issue with the power transformer, the circuit board made this build SO MUCH easier. I am VERY tempted to put together a Deluxe Reverb next.

Hey folks. A follow up. I've replaced all of the filter caps with brand new ones...and I still feel like I have the same issue. One thing Im noticing is that I am dealing with very high voltage. Like 630-640v off that first filter cap (C34/C35) and 550v at C32. Now granted, this is without a tube load, but that still seems extremely high. Part of me thought that maybe tubes in the amp would bring down the voltages some....So I decided to put some spare tubes into the amp to see if the voltages get pulled down any....that was a hasty idea, because as soon as I flipped the standby, poof - I blew the mains fuse. OK, time to back off of that idea. So I'm wondering outloud if I have a short on my B+ rail....could that result in the higher voltages, forcing a stronger draw? I traced continuity to ground with my DMM from practically every component on the B+ rail...and it all seems good. Also, the 630-640v on that first filter cap has me completely scratching my head. The most I should be getting after the SS diodes, should be 495 or so. - since I'm getting 350 a side on my HV secondary. One thing thats even nuttier, is that with the srtandby off, the HV secondaries are 350v. But with the standby on - the secondaries drop down to 300v or slightly lower....How am I getting more than 600v rectified DC on that first C34/C35 capacitor, with 300V per side on the secondaries. It doesn't make any sense. Would love to hear some recommendations, if someone has any. I'm stumped!!! Thanks, Frank

Well an update....I've been through the amp/layout multiple times with magnifiers and continuity testers. Traced out pretty much every connection. The amp looks good. Mustve been a leaky or faulty cap. Going to replace and hope for the best. Anyone know what I should be doing regarding that ground near the input jack?

much appreciated Andrea! I’ll be sure to post my results, when I’ve finally got it put together!

also thank you very much for confirming the transformer will work (in terms of the switching)!!

Hi Andrea, Good catch. In my past builds (mostly 2204 style amps. See this for reference - https://mhuss.com/MyJCM/JCM800_2204.pdf), my bias current has been taken off of one of the high voltage taps and dropped with a 220k resistor. As a matter of fact, it looks like the BIAS circuit on you BE50 Dlx schematic matches the bias circuit on my 2204 exactly - even the 220K resistor (R38). Instead of a separate transformer, couldn't I run a line to the standby switch and tap one of the main HV lines? Thanks, Frank