Real PSU or a fake ? - Page 1
Forum section: electronics / beginners

author: netdudeuk
author_rank: Frequent Contributor
timestamp: July 27, 2024, 12:45:22 pm
content: HiI'm looking to make a PSU for my 8080 project.I know that there's the challenge of bringing up and taking down the rails in the correct order but I need a starting point.I was thinking about one of thesehttps://www.ebay.co.uk/itm/115425019462?_trkparms=amclksrc%3DITM%26aid%3D1110025%26algo%3DHOMESPLICE.COMPOSITELISTINGS%26ao%3D1%26asc%3D269575%2C270398%26meid%3Db57e565869ec40269d861eaf22ca6591%26pid%3D101506%26rk%3D3%26rkt%3D25%26sd%3D125361067720%26itm%3D115425019462%26pmt%3D1%26noa%3D1%26pg%3D4247815%26algv%3DAlgoIndex5SimRanker&_trksid=p4247815.c101506.m1851The IMSA Guy seems to be using something similarI believe that MW are a decent brand, having bought them from RS before. Would you expect that the one in the eBay link would be legit and safe ?Thanks

author: BrokenYugo
author_rank: Super Contributor
timestamp: July 27, 2024, 01:03:09 pm
content: These are heavily and poorly faked, buy only from trusted distributors, (e.g. RS, Digikey, etc.)

author: janoc
author_rank: Super Contributor
timestamp: July 27, 2024, 01:23:36 pm
content: Quote from: netdudeuk on July 27, 2024, 12:45:22 pmNo.You can't know whether that generic photo even corresponds to whatever you get delivered from China (which is where that seller is). I don't see what leads to the idea that someone could guess from it whether the item is legit or that you get a poorly faked dangerous junk. And even if it was legit, you will most likely get an item that is not designed for European standards (e.g. EMI norms, PFC will be missing, protection/safety elements will likely be gutted/unpopulated, etc.)There is no reason to buy these things from eBay, esp. if you want "legit and safe". Mean Well has plenty of legit distributors in Europe.

author: netdudeuk
author_rank: Frequent Contributor
timestamp: July 27, 2024, 02:27:09 pm
content: Thanks for the replies. No, it is then.

author: CaptDon
author_rank: Super Contributor
timestamp: July 28, 2024, 01:00:13 pm
content: 8080A and the the relative supports like 8212 are forgiving to a great extent of power supply sequence. Back then 90% of the 8080 systems had linear power supplies which just sort of randomly hit their regulated point of operation. There were no power sequencing I.C.'s. The biggest thing is holding the system in reset for around 100 additional milliseconds after all supplies are stable. If I recall correctly it seems the only time I saw any actual I.C. fabric damage was in a system that remained powered up for an extended period of time with the -5vdc supply missing usually due to a shorted tantalum capacitor on the mother board. I have seen boards totally ruined when the +5 pass transistor shorted and put +8vdc or higher on the 5 volt rail. If your supplies stabilze within 200ms of each other you should be fine based on my experience of being the lead technician for all of the 8080A based arcade games from Midway that I maintained and repaired for a large route operator in central Pennsylvania as well as the games we sold to other route operators. SeaWolf, GunFight and a host of others come to mind. I still have the 1350 and 1355 backdoor keys on my master keyring!!

author: netdudeuk
author_rank: Frequent Contributor
timestamp: July 28, 2024, 03:33:39 pm
content: Thanks for your insight. I've been looking at the schematics for Altair and IMSAI hardware.https://electronics.stackexchange.com/questions/455745/why-would-a-intel-8080-chip-be-destroyed-if-12-v-is-connected-before-%E2%88%925-vhttp://s100computers.com/Hardware%20Manuals/IMSAI/MPU%20Schematic%20Diagram.pdf

author: BeBuLamar
author_rank: Super Contributor
timestamp: July 28, 2024, 05:55:38 pm
content: I don't think the one on Ebay is fake. They could buy the same model very cheap in China.

author: wraper
author_rank: Unknown
timestamp: July 28, 2024, 06:56:46 pm
content: T-50B is obsolete model. Also what's on photo is not Mean Well for sure

author: wraper
author_rank: Unknown
timestamp: July 28, 2024, 07:03:35 pm
content: Similar currently produced model is RT-50Bhttps://www.digikey.co.uk/en/products/detail/mean-well-usa-inc/RT-50B/7706371

author: ArdWar
author_rank: Frequent Contributor
timestamp: July 29, 2024, 03:17:34 am
content: Authenticity aside, I'd stay away from non-universal (manual select) input voltage SMPS. Outside of some special cases you'll almost guaranteed to get either an ancient design or one that got cost optimized to hell and back.

author: Phil1977
author_rank: Frequent Contributor
timestamp: July 29, 2024, 09:24:13 am
content: There is one trick to get better quality PSUs from China: Look for modules with active power factor correction (PFC).This way you can easily return parts that obviously do not comply with the description - if the delivered module has no PFC.If it has, chances are good that in total more resources have been spent for quality. I got a few of these 24V/10A modules:https://de.aliexpress.com/item/1005006038038971.htmlThey have a very nice mechanical design, use reasonable electrolytic and Y-caps, have a reasonable earthing concept without significant common-mode AC current, use good transformers and are comparatively low-noise. I couldn't find anything to complain about so far.Authentic Meanwell units are of course the best choice.