The bulb tester is before the soft start. It only tripped once, so far. I didn't tried to bring it to 30 mV strictly next time. Just observed a very bright light bulb and went above 20 mV on R30.
if the voltage after the bulp goes below 85VAC the softstart reset and releases the relays.
and a 40W bulp is 1.3Kohm. => 30mV bias is 600mA => two channels is ~180mArms => 180mA * 1.3K => 230Vrms drop across the bulp.
and a 40W bulp is 1.3Kohm. => 30mV bias is 600mA => two channels is ~180mArms => 180mA * 1.3K => 230Vrms drop across the bulp.
To be honest, I'm puzzled. Should I go without the soft start, or without the bulb? I was adjusting one channel only and it looked very bright. That should've been only 117Vrms across it?
Let the softstart in the circuit and remove the bulp.
If the softstart is broken i will replace it.
If the softstart is broken i will replace it.
I have managed to bias both channels and get the offset below 10mv. Not without a little smoke though, at first. I can only suppose, one channel trimmers were not set right at the beginning. Otherwise, I have no explanation why that smoke appeared after some 30 sec after powering it up. I guess it was C6, because when measured with laser thermometer, I've got 60C even sometime after a shutdown. Now everything looks OK. Different power resistors are hot. Just above 60C. Otherwise they measure the same bias voltage.
Should I check something more before hooking it up to the main system?
Should I check something more before hooking it up to the main system?
mmmhh. Sounds like a good explanation, i cannot see why else.
I think C6 get heated by the other parts.
I think C6 get heated by the other parts.
I have to go through all kind of events (nothing DIY related), untill I hook it up. Treasuring the moment. Will let you know. I hope it's over the weekend.
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