duffy
Well-Known Member
Yes, you should see the 20khz on pis 11 and 14 - and also on 5 and 6. These are the RT and CT lines that run the oscillator. Pin 5 should show you a sawtooth wave.
The +150V should pop up almost immediately. The chip shouldn't blow if the fets are disconnected...
Put two .1uf caps on the +12V lines on pins 13 and 12, as near to the chip as you can get. In the past I have had problems with harmonics and high frequency mosfet coil drivers. You would think the 10μf cap would take care of it, but they are surprisingly unresponsive to high frequency harmonics (like 1mHz or more) and I can tell you from first-hand experience this particular problem will blow drivers and fets.
You are using a sensible approach to build it in stages and debug each stage, and to try operating it without the feedback connected to see if that's an issue. You could also disconnect that /Shutdown line during debugging to see if that's causing the problem.
The +150V should pop up almost immediately. The chip shouldn't blow if the fets are disconnected...
Put two .1uf caps on the +12V lines on pins 13 and 12, as near to the chip as you can get. In the past I have had problems with harmonics and high frequency mosfet coil drivers. You would think the 10μf cap would take care of it, but they are surprisingly unresponsive to high frequency harmonics (like 1mHz or more) and I can tell you from first-hand experience this particular problem will blow drivers and fets.
You are using a sensible approach to build it in stages and debug each stage, and to try operating it without the feedback connected to see if that's an issue. You could also disconnect that /Shutdown line during debugging to see if that's causing the problem.
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