I have a Boyuurange A-50 MKIII. I watched all of Stephe’s modification videos. I don’t understand schematics but can solder and have rudimentary knowledge about using a multimeter. So I decided I could follow the videos and do what he did even if I didn’t understand it. What a mistake! I did all mods, put tubes in, powered up amp, and blew it’s fuse. Ordered new fuses. After having worked on the mods on my kitchen table for 2+ weeks, my wife was out of patience so I moved to garage workbench. I put new fuse in, turned amp on, and tripped the ground fault interrupter (we didn’t have one in the room where I had blown the fuse). That gave me a clue to what was wrong. I opened the back cover and discovered I had pinched the orange insulation to the bare wire that runs from the AC receptacle to the on/off switch. The wire had grounded against the chassis. It was intact but scorched. I applied some liquid tape and turned the amp back on. The lights on the meters came on, the ground fault interrupter didn’t trip, but no sound came from the speakers. I took the tubes back out, turned it over, and checked the points for voltage that Stephe had checked in the videos. There was no voltage anywhere, so I decided I must have blown the power transformer even though I didn’t know how to actually check it. The Tube Amplifier Store got the factory in China to ship another transformer for about $159 including freight. I put it in but still had no voltage, so I decided the on/off switch had been damaged. I put a new one in and still have no voltage. I’m stumped. Any ideas?
Below is a step-by-step of what I did.
FRONT END REBUILD
ALL REFRENCES TO “SIDE” ARE FROM FRONT VIEW OF AMP WITH AMP UPSIDE DOWN
(1) Black wire that runs from Pin 2 to Pin 4: (Stephe repl w/white wire)
· Disconnect other end from Pin 4 and solder to Pin 6
(2) Grid Stopper
· 1K, 1W (101001JR500) Cut both leads short, cover resistor w/ H.S. & solder to yellow wire .—
Will connect to Pin 1 at step (9)
(3) 1M, 1W (101004JR500)
· PFTE tubing to wires & solder Pin 1 to Ground & cut lead short after
(4) 47K, 2W (204702JR400)
· Solder to Pin (5) and to B1 (under board with some lead sticking out)