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I finished my 18w plexi build this past weekend and it sounded great. I decided to install the full power VRM and went to test it out today. Upon my first test I had not switched the 1M resistors or added the caps between the 68k resistors and the tubes. Powered up fine but when I switched off the stand-by I got an interesting little lightning show in the rectifier tube and quickly switched it off. Rechecked and realized I had more work to do. Completed said work and still got a lightning show in the rectifier and then the fuse blew. I'm wondering if anyone else has had a similar experience. Photos added of the chassis and close ups of changes made (.047 cap added between 68k and v1 tube pins per layout, changed 1M resistors to v1 pins to ground per layout and added a .022 cap to the input jacks in place of the 1M's). I'm sure I could change it back stock, but I'd like to experience the VRM before deciding. Thank for the help.

The cap and resistor would not cause the problem your experienced. More than likely the back metal of the mosfet is touching something like the screw holding in place . Or the screw right beside it. I can't remember which pin but none should measure 0 ohms to the chassis

agree with sasafraz. is the grey sil pad in place? was there a burr that penetrated the grey insulating sheet?

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Stephen
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Thanks for the replies. I ended up pulling the vrm after all. Mainly to see if I had done damage to the rectifier. The seal was in place and I took care to make sure nothing was touching Since it Was so close to the screw. Sounds just fine without the vrm and I use an attenuator to tame the volume for church gigs. If I get to feeling figity I might try to reinstall. But all is good for now. Thanks again