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Big Tom

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  1. Very good information, and spot on! The old guy here at work went digging through some old text books and found a couple articles on them including the SG series devices like the blown one, Surge-Gaurd circuit protection devices, NTC Thermistors just like you said. I already had checked the rectifier and it's a pretty beefy SOB and checked out fine, ie removed, meter tested, then hooked up elsewhere and load tested. I didn't check the filter caps though, hadn't thought much about them since again pretty beefy but for sure I'll look into those since it'll be a couple days for my FETs anyway. I understand there is a chance this PS might be a complete writeoff, it's for work though and I work for a power company so money isn't a huge deal and they've already ordered a new replacement PS to the tune of over $1K I believe... so this is kindof a play thing for me, if I can get it fixed/tested/working we'll throw it into stores in case of an extreme emergency we can use it. We use these power supplies for our data acquisition system at one of the plants, so really they would much rather replace with new then a reconditioned old unit... but again extreme cases have happened where a working rebuilt might be needed so it's a good thing to try and at least get it repaired
  2. Very true, I already have the replacement power MOSFETs on order since one of the old ones was cooked causing a short and popping the SG57. But more digging around and it looks like it's actually a Thermistor not a Varistor, hard to determine what a device is when it's blown up and the company is no longer and the part number isn't much help! :D But yeah I still need to find something for a replacement, the SG57 was actually in series with the AC line of the bridge rectifier. I'm asuming once I get the FET's all replace I can throw in a decent sized resistor instead of the Thermister and try powering it up, at least that way if there is more to the short then I originally thought it shouldn't cook anything, and if things look good it should power up without any load attached
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