Chinese LM-317K  TO-3 regulators  - Any suggestions on which one to buy ? - Page 1
Forum section: electronics / projects

author: ez24
author_rank: Super Contributor
timestamp: August 20, 2015, 08:11:17 pm
content: http://www.aliexpress.com/wholesale?catId=0&initiative_id=SB_20150820115836&SearchText=lm317k+to-3From this page I can see at least two different markings. So I was wondering if anyone can make a suggestion on getting some.Anyone have any bad experiences with these. I will be using them at mid power rating.If one or two are Chinese brands - do Chinese counterfeit from each other? Or put another way - could I assume one company makes all the ones with the same markings?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 20, 2015, 08:13:13 pm
content: Replacements...??Please tell me you aren't designing something brand new that's using those poor old bastards!Tim

author: ez24
author_rank: Super Contributor
timestamp: August 20, 2015, 08:32:46 pm
content: QuoteYes just for personal hobby use. Why poor old bastards? After all I am an old poor bastard alsoI want to use them at the output of a buck for 2 amps for breadboard experimentation. A 19v laptop ps will be used for the buck. I want 3.3v, 5v, 12v and adj volt outputs.According to the LM317 datasheet, the LM317 has good ripple rejection at 65k (one persons ripple measurement). In other words this regulator has good high freq rejection from buck convertors. I have eliminated LDO because their datasheets show considerable less ripple rejection.Since I have not ordered any LM317K (I have TO-220 versions), I am open to other suggestions.

author: SeanB
author_rank: Super Contributor
timestamp: August 20, 2015, 08:41:00 pm
content: They will almost certainly be either fake or recycled units. If you do user them test before use to ensure they will actually work, and are not a random remarked transistor.

author: ez24
author_rank: Super Contributor
timestamp: August 20, 2015, 08:54:15 pm
content: I will test them - even if only 1 out of 10 works, it seems a better way to golook herehttp://www.newark.com/webapp/wcs/stores/servlet/Search?catalogId=15003&langId=-1&storeId=10194&gs=true&st=lm317k1 - LM317k = $39.15 + $20.00 shipping !so in round numbers I could get 30 from China vs 1 from the US ie 30:1 price ratioso if 50% failure rate the price ratio would be 15:1

author: wraper
author_rank: Unknown
timestamp: August 20, 2015, 08:59:15 pm
content: Quote from: ez24 on August 20, 2015, 08:54:15 pmThat is LM117KBetter to not get anything. Why you would want to get voltage regulator in TO-3 these days? As of Chinese LM317, they sell even fake 7805 in TO-220, so you should guess what you'll get in more expensive case.QuoteYeah, 50% failure ratioin your deviceAnd you'll never know when it will go out. Likely will take something connected to the output too.

author: DimitriP
author_rank: Super Contributor
timestamp: August 20, 2015, 09:07:19 pm
content: Quick search on mouser and came up withhttp://www.mouser.com/ProductDetail/STMicroelectronics/LD1084V/?qs=sGAEpiMZZMvYvv22R2xfeJmkB8Fae5TFOd%2fkwRzNnwE%3dLD1084V for a whole buck-fifty

author: ez24
author_rank: Super Contributor
timestamp: August 20, 2015, 10:13:04 pm
content: QuoteActually I was going to use this until I studied the datasheets between this and the LM317 - the charts on ripple rejection at about 60 kHz. The LM317 has significant more db rejection than the LD1084VI know the 317 uses more power than the LD1084, but I made the decision to go for lower ripple vs lower wattsIt seems the LM317 is NPN and the LD1084 is PNP. And NPN based regulators have better high freq ripple reduction (based on the two datasheets)( probably in the physics somewhere)thanks for the suggestion

author: DimitriP
author_rank: Super Contributor
timestamp: August 20, 2015, 10:58:52 pm
content: Quote from: ez24 on August 20, 2015, 10:13:04 pmI guess its one of those: part you can trust vs price vs claimed performance , pick any two

author: wraper
author_rank: Unknown
timestamp: August 20, 2015, 10:59:49 pm
content: Quote from: ez24 on August 20, 2015, 10:13:04 pmWhat should this mean?QuoteLD1084 has NPN pass transistor.

author: onlooker
author_rank: Frequent Contributor
timestamp: August 20, 2015, 11:33:40 pm
content: On ebay, you can have 10 Lm317k TO-3 for $7.50. They may not have guaranteed quality or spec, but, for hobby use, the OP may want to try them out and report results back here.These things are easy to test and I think get refund for fake/non-working ones are mostly just involving contacting the seller. I recently bought a few 110V LED bulbs for a few dollars. One was DOA (but, fixable) and all were half of the speced wattage. I just left negative feedbacks without wanting to go through the refunding process. Then, the seller "begged" me to accept the refund for both, in exchange for removing the negative feedbacks.

author: wraper
author_rank: Unknown
timestamp: August 21, 2015, 12:01:21 am
content: Quote from: onlooker on August 20, 2015, 11:33:40 pmFor hobby use buy genuine LM317T in TO-220 and not obvious fakes or salvaged old parts which are sold as new (if you are lucky). I just don't get why someone in sane mind would use them at all, especially considering their dubious origin.

author: onlooker
author_rank: Frequent Contributor
timestamp: August 21, 2015, 12:23:05 am
content: Maybe, you have first hand experiences about these LM317 TO-3 to see the obvious. Then, you can tell your story. I am really curious to know what is in there.I did buy a LM317/337 kit from ebay a while back. Nothing is obviously wrong or bad. Then, I did not test them to the limit.

author: rdl
author_rank: Super Contributor
timestamp: August 21, 2015, 12:29:15 am
content: I was not aware of any real difference between TO-3 and TO-220 for LM-317 regulators other than possibly slightly better noise resistance. Some of the other LM series regulators have an additional pass transistor that may benefit from better heat dissipation of a TO-3 package, but the LM-317 does not have one.