Broken Passport Plus
Tue, 31 Aug 2021 09:15:41 GMT
Hey all, this is my first post here and I have a big ask. I traded for a broken Passport Plus a few weeks ago hoping it would be an easy fix. I couldnt get my LWS or Miller to give up any board schematics or tech info beyond the troubleshooting schematic in the machine. So I said to heck with em and started probing and desoldering. Turns out, all the IGBTs and diodes were good but I found a bad zener diode in the supply to the microprocessor on the main board PC-1 as its called. Ive got all the new components coming, but Im nervous to fire it up without being able to test the rest of the low voltage supply section. A lot of the smt components are un marked and I dont want to fry the new zener diode which is a 40 cent part thatll take forever to change again once the machine is assembled if i can avoid it. If anyone has access to some board level info I would much appreciate it the machine serial is mc051458n Also If anyone has a board with a different failure or a complete machine Id buy it. Any help would be greatly appreciated.
Reply:Can't help you on the board schematics but I can send you the technical manual that covers your s/n. PM your email address to me and I'll send it if you're interested.
Reply:Thanks for that! looking forward to getting this thing up and running!
Reply:You're welcome. Good luck
Reply:I went over the tech manual and its great! Its got voltage readings for the test points on all the boards. It also has a list of other documents not in the tech manual including schematics! You have already helped me so much, but could I beg another favor and maybe get them as well? The document numbers are:219 051-A 234 033-A 234 027-A 235 780-A You have already been so much help, if I manage to salvage this thing, I'll owe you a board repair! Also, is this info that my LWS counter man would have access to but maybe he doesn't know where to look? I have been working with the same guy for almost 20 years and he's great.
Reply:Some counter people don't know how to fix anything(some don't care if you do or not), some companies would rather you have their service dept change the components so giving out tech manuals cuts into their business.Miller can be touchy about end users getting tech manuals for current or late model equipment also.Sounds like you figured it out! good deal!
Reply:jmmorriso, check your PM
Reply:I'm gonna keep his name anonymous so he doesn't get bombarded with requests for info, but thank you to a very special board member for helping me out! I got schematics this morning and am getting large copies made up so I can see all the little traces. Hopefully I can get it figured out tonight and I will post what I find.
Reply:Well no luck yet, but I did learn that what I thought were sot23 package zener diodes in a couple places are actually transistors, so I'm gonna order those now. No wonder they were testing as bad!
Reply:After more hours than even makes sense, I believe I have found the culprit. A zero ohm fuse! Only thing is I have to pull the diodes and igbts off the board, and remove the "wind tunnel" again to test it, along with a few other things. I should have waited for the schematics before I reassembled it. Also, wish the PDFs were searchable, because that's one of the things I was looking for as a possible failure point.Last edited by jmmorriso; 08-06-2018 at 07:19 PM.Reason: Typos
Reply:Found a bad resistor on the mosfet that drives the transformer that drives the igbt, I was wrong about the 0 ohm resistor. There's parts everywhere. Too emotionally invested to give up!
Reply:Originally Posted by jmmorrisoFound a bad resistor on the mosfet that drives the transformer that drives the igbt, I was wrong about the 0 ohm resistor. There's parts everywhere. Too emotionally invested to give up!
Reply:Still no clue if thats for sure whats wrong. Gonna replace everything on either side of the bad resistor. If i gotta desolder it to test it i might as well have new stuff standing by. Having one or two igbts (if the driver is bad) not firing explains why it wouldnt chooch. Once i borrowed an oscilloscope and checked all the serial and pwm lines i could find its kinda making sense. Im reverse engineering an education in electronics! Wish so many of these board components werent already obsoleted because of lead free and rohs garbage reasons. I have been swimming in toxic heavy metals since I was a baby and im fine. Everyone has webbed toes right? I have so far beenable to find the new equivalent parts though.
Reply:I replaced the mosfet and the driver, got that problem solved but managed to screw something else up. the relay for the precharge circuit wasnt pulling in so i figured i would short it to ground. BAD IDEA!!! I let some smoke out of the flyback? transformer on the main board and am having trouble finding one. Anyoune have a main board from a passport or maxstar thats dead? My guess is that its a custom job and I wont beable to just buy one. I have poked and prodded so much without breaking anything worse than it was, and now that I was so close to victory I have failed. Now that im familiar with these I think i can ACTUALLY fix one in the future.
Reply:Originally Posted by jmmorrisoI replaced the mosfet and the driver, got that problem solved but managed to screw something else up. the relay for the precharge circuit wasnt pulling in so i figured i would short it to ground. BAD IDEA!!! I let some smoke out of the flyback? transformer on the main board and am having trouble finding one. Anyoune have a main board from a passport or maxstar thats dead? My guess is that its a custom job and I wont beable to just buy one. I have poked and prodded so much without breaking anything worse than it was, and now that I was so close to victory I have failed. Now that im familiar with these I think i can ACTUALLY fix one in the future.
Reply:They sell the whole board for like $1200, which i understand why it would be so expensive since Miller is marketed to professionals bla blah blah downtime is more expensive than repair blah blah. But it's still freakin crazy expensive! Id rather try to sell the remaining parts on eBay and buy another project, but im not giving up yet. Especially since the screwup is on me now.
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