Component testing



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Component testing

Postby cherler » Mon Dec 04, 2017 10:10 am

So I'm working on verifying a new PCB, and the good news is it is verified! It was a huge pain in the ass though. I have some BJT's on switching duty for a group of relays, and for the first time I actually had a bad BJT. Maybe this is actually more common than I thought, but I've never run into it before. After a few hours of trying everything else, I clipped it out and popped a new one in and everything was totally functional.

So what do y'all do for component testing? Is this actually rare enough to not worry about too much? Do you bother testing every component? Is there any hot tech for component testing you like? I would love to not have to deal with this shit again :lol:
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Re: Component testing

Postby BetterOffShred » Mon Dec 04, 2017 11:22 am

I do not test every component. It's just not realistic. That being said, I do test transistors and socket them and all chips. I have a little Chinese tester called the mega-328 and it tests most stuff pretty easy. I use my DVOM for some things but if it's a quick cap or transistor test, it goes in the 328.
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Re: Component testing

Postby crochambeau » Mon Dec 04, 2017 11:33 am

Unless I'm matching parts or picking through undocumented part numbers I generally don't bother, unless it's a sensitive circuit under development. Sometimes it's fun to test a few transistors out of a new batch.

I typically build more than one PCB at a time, so any odd failures can be compared to a working version. Troubleshooting happens, but it's made easier if you have a functional example kept on hand.

For testing I also have a 12864 Mega328 that works well enough, it's still a slow process, but I can imagine it would fit certain workflows.
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Re: Component testing

Postby eatyourguitar » Mon Dec 04, 2017 12:04 pm

It largely depends on the provenance of the components in question. if they came from mouser then they are good. if they came from UTsource they could be fake. If they came from Rochester they are real but they are also surplus therefor possibly vintage and possibly not stored or shipped properly. Rochester does spot checks. UTsource no checks. Mouser only sells new direct from the manufacturer. If you buy a pile of random parts in an estate sale I would test every one. if you have had parts stored in your cold wet shed for years I would test every one. if you accidentally mixed up the bag of blown and salvaged transistors with the bag of new transistors then I would test every one. I mostly don't use sockets in pedals but I have various different sockets and testing jigs to quickly identify failed BJT before I solder it into a new home.
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Re: Component testing

Postby cherler » Mon Dec 04, 2017 3:47 pm

Yeah I guess this would be less of an issue once I've verified the PCBs and I'm sure I like them. Since this was the first one I soldered up I had no idea where the error could have been hiding. Maybe it's worth a little more testing just getting the first board up and running smoothly, and from there a working one is available to test against. Thanks for the mega328 recommendation, I'll check that out!
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Re: Component testing

Postby cherler » Tue Dec 05, 2017 5:23 pm

Got an update for what it's worth, turns out I actually shorted two pins on the QTFP package I chose for the PIC. With the short I don't think there was enough current available to open the transistor all the way. I replaced a 2n3904 with a 2n5089 since I ran out of the former. Higher current gain and suddenly everything works. Mystery solved! :lol:
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Re: Component testing

Postby BetterOffShred » Tue Dec 05, 2017 6:39 pm

You ran out of 2N3904's? :wha?:

Nah JK.. glad you got it fixed :)
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Re: Component testing

Postby Mellissengeist » Tue Dec 12, 2017 7:46 am

Did you had a look on those Component Testers floating around the net?
https://www.ebay.de/itm/272449097144
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Re: Component testing

Postby eatyourguitar » Thu Dec 14, 2017 6:41 am

One time mouser was selling a specific batch of 1N4001 for $0.01 as a clearance close out end of life deal so I ordered 500. When my package arrived I guess what happened is they sold more than they had in stock so to compensate me they surprised me with 500 units of 2N3904 for $5. The 3904 obviously being much more valuable at $0.40 each in small quantity. I will never run out. This is why I like mouser. They probably figured out that I buy a shit load of silicon transistors and selected them for me based on the rest of my order. I also never need to test them like I would with a cheap bulk surplus order somewhere from Hong kong Shenzhen etc..
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