Hi people, yes its all about another dead control board. This particular board was in a Warco super mini lathe AKA the 14" Chinese lathe smoke generator
Having spent several days reading the interweb of gloom I ended up here with what looked to be a promising thread on this very subject posted back in 2009.
Right from the get go, my electrical expertise is complete novice so go easy on me please.

Basically the lathe decided to stop spinning but left the RPM counter illuminated. After taking the control panel off to investigate the issue the lathe sprang into life at full speed though it wasn't dialled in for that and it worked for around 2 seconds before it decided to release a bolt of lightning and some magic blue smoke.
Having scoured the above thread for inspiration I have isolated the main control board from the auxiliary filter board to determine what needs attention. The filter board if totally fried with several track blown completely off the pcb! I'm guessing there's some kind of spike damage to the main board.
I have replaced the whole row of MOSFETS (2 x S8020L scr1&2 and 3 x D8020L d13,14 and15) as i tested them they were all suspect and cheap to replace. Following the guidance from the KB installation and test procedure I ran AC mains to L1 and L2 with the speed pot connected but set to zero and the motor connected to A+ / A-
Instantaneously it blew the 3A fuse in the mains plug. After taking a look with my DMM set to continuity I began to look for a dead short, again following guidance from elsewhere suggesting that MOV1 and the capacitor are across the mains. These do not appear to be shorted but have been removed from the board to aid fault finding.
So here's where I'm at and can't get past this?
I have continuity between L1 and the heatsink on scr2, there doesn't appear to be any bridging on the back of the board and I cant seem to see any components that bridge the tracks that I can test for a short?
Yes I know that its fairly easy to get hold of the more popular KBIC - 240D and this will soon be on order but I want to know what's causing my workshop to be full of blue smoke for when it eventually goes again.
Please don't respond with, just dump the controller and fit a 3 phase motor because I already have a bigger lathe and don't want to reinvent the mini lathe into something it was never meant to be. Well, not yet anyway.
Thanks in advance.

Similar Threads: