eBay is full of LM317/LM337 power supply modules - but are any actually good? - Page 1
Forum section: electronics / projects

author: cvanc
author_rank: Frequent Contributor
timestamp: December 23, 2018, 05:11:28 pm
content: There are a ton of premade power supply boards on eBay, a large sample is shown herehttps://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=lm317+lm337+supply+-%28bare%2Cboard%2Cpcb%29&_sacat=0&LH_TitleDesc=0&_sop=15&_osacat=0&_odkw=lm317+lm337+supply+-%28bare%2Cboard%29&LH_TitleDesc=0Most consist of bridge rectifier/filter caps/dual regulators, but some include the transformer as well.Even the most expensive of these is cheaper than anything I can piece together, so they're pretty tempting. Has anyone here got experience with any of these? Do we have opinions on which are good and which to be avoided?Thanks.

author: Synthtech
author_rank: Regular Contributor
timestamp: December 23, 2018, 07:29:17 pm
content: I bought a couple of those as kits some time ago, very cheap. I bought them just to have a couple of spare boards to have around for putting into small projects as a temporary +/- 15V supply.They came as a kit with board and parts and a couple of small heat sinks. I built them and tested them and running unloaded they did as advertised. Voltage could be set for each rail with the trim pots and it all looked good. Once under any kind of load the negative rail collapsed and drew a lot of input current. As they were a few bucks each I tossed them into the “one day I will take another look at them” box. Both had the same issue. Probably fake LM337’s supplied with the kit or the board had a fault it or incorrect silk screening (you have to use the silk screen as a construction guide). I wasn’t interested enough to have bothered trying to figure out the issue yet. Might of been me not paying attention and making a careless error during assembly but it’s a very simple board and it works fine unloaded.

author: soldar
author_rank: Super Contributor
timestamp: December 23, 2018, 08:27:08 pm
content: I have bought and used a couple as well as other, similar devices and my comment here is in general, about similar small electronic boards, not specific to the power converters.Generally the heat-sinks are very small. They are adequate for small loads but you need bigger heat sinks for bigger loads. I have found this to be true also with Triac power regulators. The semiconductor was capable of handling more power if fitted with a larger heat-sink.Other than that they have worked fine.When the semiconductor is placed sideways, near the edge, It is easy to place a metal block with a hole and increase the cooling without even unmounting the semiconductor from the board.

author: floobydust
author_rank: Super Contributor
timestamp: December 23, 2018, 09:08:35 pm
content: I find they use low quality IC's, they are the 1/2 gauge thin-tab TO-220's with a very noisy output.The heatsinks are too small to get much out of them, and they have no protection diodes on the outputs.

author: precaud
author_rank: Frequent Contributor
timestamp: December 24, 2018, 04:32:06 am
content: I bought some unpopulated pcb's and used my own parts for a couple. The layout was adequate.