Sorry. I know nothing of transformers. I am using the crippled F4 board. I do not have the diodes on the FE as I thought they were there to protect the Jfets, but I relize now, they would have kept DC off of the input. I don't have R1-4, D1-2, Q1-2. Input is jumpered to between the electrolytics.
wrong ; they're here to protect input jfets of too much of input swing
so - now - besides xformers , you forgot that caps also have virtue of decoupling DC ....... when properly implemented , you also will not have any spikes.
what's value of input shunt resistor , or you didn't put that one ?
in other words - you need that R2 , as bleeder resistor for coupling caps ; without it , you have pre-stage zapper , not output amp
I'm curious - which DAC you fried ?
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if interconnecting is in case , you always need to have that - for discharge of cap
I have another mystery. On my second BA-3 set of boards, I have everything adjusted and all looks good in terms of DC operating points. When i hook up the left channel to the output stage, the bias across the source resistors in the channel it hooks to drops by 200mV or about .5A. Is this an indication of a problem with the fets in the BA3 Fe? It does not do it when i hook up the right channel from the BA3 FE. It would seem that something is shunting the current away. Checked RCA connections to make sure no short to the case, but that would affect pre-connection readings anyway, so it seems it is happening on the FE board.
The right FE channel works fine on both output channels. The left FE channel causes the bias on output resistors to drop. I assumed some sort of ground loop or short, but couldn't find anything. Fired up my oscilloscope for the first time. I am probably going to destroy something very soon.
be sure that either amp or scope are off safety gnd - in case that you connect gnd probe to live output
first time when that happens to me , I spent entire afternoon searching why fuse blew ......
dumb ZM .......
(off course that best solution is that both amp and scope are on safety gnd , and black probe on output gnd
)
first time when that happens to me , I spent entire afternoon searching why fuse blew ......
dumb ZM .......
(off course that best solution is that both amp and scope are on safety gnd , and black probe on output gnd
)
I only have one probe and have never used an an oscillosope. I managed to calibrate the probe,... I will try not to make the magic smoke. I do not have a signal generator, so this may be excercise in futility. I assume that I connect probe to output fo the amp. what do i do with ground clip?
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