Electronics > Beginners
Lm317 vs LM338
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Mr. Scram:

--- Quote from: exe on August 26, 2019, 06:43:23 pm ---"The Greedy Pay Twice".

--- End quote ---
"He Who Resorts To Sayings Seems To Have Run Out Of Arguments".

We can go over this again and again but the vast majority of Chinese parts work fine and vast differences in disposable income exist. There's not much more to be said. Continuing to foul up someone's thread isn't productive.
janoc:

--- Quote from: Mr. Scram on August 26, 2019, 06:25:02 pm ---We're obviously talking about learner and hobbyist territory here. If you buy Aliexpress components when you're doing customer work you're just an idiot. Not because it'll definitely blow up but because the risk reward proposition is completely skewed. Just charge marginally more and cover your ass.

--- End quote ---

Yes, absolutely. Sadly it is sometimes difficult to convince the folks in charge that saving 10 euro on shipping costs could well cost us thousands in wasted time and troubleshooting customer issues. (And still ignoring the fact that 10 bucks gets you second day delivery vs. 3-4 weeks from AliExpress).

But that's a different debate, not very relevant to the OP's issue.
magic:
Don't you people have shops, internet stores and auction site sellers who specialize in hobby stuff? Inexpensive shipping by snail mail, small quantities of common parts, either from reputable Western distributors or trusted and verified Asian sources? There surely is a bunch of such vendors in Poland :-//
You can sometimes get fakes but at least it's fakes that work (or somebody would have complained before you) and the more professional sellers take it seriously and change suppliers if something fishy is found.

Going back to OP, I don't think it's caused by failing to meet the minimal load spec or even lack of reverse protection diodes. Somebody suggested that perhaps peak voltage from the transformer exceeds 40V. That's worth testing - just measure it with the diode bridge and capacitors in place but without the LM338.
If not, the regulators may be fake. As I said yesterday, test them at low voltage and see how they behave.
dcbrown73:

--- Quote from: exe on August 26, 2019, 06:43:23 pm ---
--- Quote from: Mr. Scram on August 26, 2019, 06:22:38 pm ---the discussion is irrelevant to many as they simply don’t have the beer budget for original parts. Regardless of assessments it’s the “wrong” approach.

--- End quote ---

"The Greedy Pay Twice".

--- End quote ---

That is only true occasionally if you learn from mistakes.  It shouldn't happen all that often.  There are reputable Chinese component sellers out there that at least sell functioning parts.

I've bought many from Amazon that work and they usually come with several in a package.  I've had to toss out one before, but I had 4-9 more from the kit.  That has happened maybe three times since I started this in 2014.   

I'm in agreement that if you're buying parts for a customer's device or a product you are selling.  Buying high quality parts are a must.  Otherwise, your products will end up being sold at the $1 store, or nobody will send you products to fix due to inferior product life after fixing it.

On a hobby bench while learning.  Buy from a trusted reseller.  Chinese or not unless you building / repairing something you expect to use for a long time to come.

I built a Elenco power supply kit and I replaced the electrolytic caps with higher quality ones during the build, but as for the diodes, resistors, and ICs that came with it.   I used what was shipped.  I sent it to a friend so he could enter the electronics hobby and I expect it to last him a long time or at least until he upgrades to bigger better PSUs.
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