K7400 HV shutdown with no ticking

pun84

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When I power my chassis up I can see the HV jump to 9kV for about a second then quickly drop down to zero.. B+ is at 160VDC and when I hook up a bulb it drops to 120VDC like it should.

Tried changing the LA7851 and still no luck, I am pretty sure its not the flyback... could it be the vertical output IC?

Am I reading the schematic right? C729 is a 10uF 50V Bipolar Cap? is that what they mean by NP in the schematic.. ?
 
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Sounds like your startup circuit isn't working. There is a resistor there (R760?) that sometimes goes open...
 
Got it to work!


I am pretty sure it was that I had a polarized cap in C729.. replaced it with a 10uF 50V NP.

I also found a solder bridge short on one of the pins for the socket I had installed for the LA7851 IC.. The short was so tiny it couldn't be seen with the naked eye.. had to use a ohm meter with beep mode on!

Really wish Wells Gardner didn't put polarized markings on the board where non-polarized capacitors go.. :]
 
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