This is my first post at diyAudio, and I come looking for help with my Tubelab SE build. I usually do restoration work, and I have a good amount of experience with tube equipment, but I am still a hobbyist. I usually hang out over at Audiokarma, but I'm trying some DIY.
I'm building the amp to use with 2A3's. I powered up the amp with no tubes like the instructions say, and the filament voltages were right at 2.5v, the B- was around -200VDC, and the B+ was slightly negative, -14V or something like that. I next installed the 5AR4 rectifier and powered on. The rectifier warmed up for several seconds as you'd expect, but when the B+ started ramping up, it kept climbing until the rectifier sparked and shorted. I think it was at around 500 or 600VDC by the time I realized what happened, but it was pretty quick.
I am seeing 5.3 VAC or so at the rectifier filaments without the tube installed, and around 580VAC between T1-4 and T1-5 with no tube installed.
I am using a Hammond 270HX power transformer. A Triad C-14X choke is in place of R4.
C4 is 4.7uf 450v, and C5 is 150uf 450v with a 100uf 370 VAC motor run capacitor wired in parallel with C5.
I have checked my work over and over, and I can't find anything. I am hesitant to fire it up again with another rectifier until I do some more troubleshooting. It seems like there must be some kind of short in the B+ supply, but what else could cause the rectifier to short and B+ to keep climbing? Any advice on what to look at next is very appreciated.
I'm building the amp to use with 2A3's. I powered up the amp with no tubes like the instructions say, and the filament voltages were right at 2.5v, the B- was around -200VDC, and the B+ was slightly negative, -14V or something like that. I next installed the 5AR4 rectifier and powered on. The rectifier warmed up for several seconds as you'd expect, but when the B+ started ramping up, it kept climbing until the rectifier sparked and shorted. I think it was at around 500 or 600VDC by the time I realized what happened, but it was pretty quick.
I am seeing 5.3 VAC or so at the rectifier filaments without the tube installed, and around 580VAC between T1-4 and T1-5 with no tube installed.
I am using a Hammond 270HX power transformer. A Triad C-14X choke is in place of R4.
C4 is 4.7uf 450v, and C5 is 150uf 450v with a 100uf 370 VAC motor run capacitor wired in parallel with C5.
I have checked my work over and over, and I can't find anything. I am hesitant to fire it up again with another rectifier until I do some more troubleshooting. It seems like there must be some kind of short in the B+ supply, but what else could cause the rectifier to short and B+ to keep climbing? Any advice on what to look at next is very appreciated.