Today has been a nice and interesting day. I finished a mini T2 with active battery. The copper color board on right side in picture in previous post.
Late afternoon I were ready for the first power on. One DMM to measure one side verses ground and another to measure the other side. High voltage clicked in – no explosion – on side showed a few volts verses ground while the other almost 400 volt verses ground. It took some time for me to realize that the 400 volt reading in fact was the BIAS. I’m getting to old for this. When I found the right measuring points I had very nice readings. Batteries are always interesting. Readings as follow. Left +194V and -443V, right +196and –443V. So they also seem to be alright. (using 640V instead of original 740V)
Connecting headphone. Very noticeable hum but the music sounded good. After a while very annoying noise came. The noise almost disappeared when I approached the trimmer with the screwdriver but came back when I pulled back my hand.
Turned power off and changed the small tubes, power up again, lower my guard and went for a cup of coffee and… it all exploded…
So tomorrow I have to fix the power supply for the second time within a week. On amplifier board visible; burned traces, resistors and one popped transistor. Maybe I should feed ducks.