I was probing the power supply mosfets and discovered this anomaly. With the amp sitting on my bench with the power terminals to my left. The top row of power supply mosfets output looks like this in the attached photo. The bottom row of mosfets mirror the output of the TL494 so they look normal. The 4 drivers all have The expected wave form that is a mirror of the output of the TL494.
Probe is 1x at 2 volts per division.
David
Probe is 1x at 2 volts per division.
David
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Sure thing Perry. I know your trying to help and I’m making it hard for you to. I apologize.
The picture above was taken with the probe grounded to the negative terminal and the probe was on the source leg of any of the top row of power supply mosfets.
With my probe grounded to the same place the probe on source leg of any of the mosfets on the bottom row of power supply mosfets I get this.
Am I not grounding my scope to the right place?
David
The picture above was taken with the probe grounded to the negative terminal and the probe was on the source leg of any of the top row of power supply mosfets.
With my probe grounded to the same place the probe on source leg of any of the mosfets on the bottom row of power supply mosfets I get this.
Am I not grounding my scope to the right place?
David
Attachments
Right you are sir. I just found it. It was hiding under a speaker wire spanning across the bottom of the circuit board. Moved it out of the way and there it was starring at me. In the attached photo the red probe is pointing at it. Learned a good lesson tonight.
Thanks a million for you help Perry. Amazing!
David
Thanks a million for you help Perry. Amazing!
David
Attachments
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