poorly psu - Page 1
Forum section: electronics / repair

author: tekguy
author_rank: Contributor
timestamp: September 26, 2022, 03:43:33 am
content: hi all,i have this non working lab psu 0-30v-05a,its labeled as a sktronic 650.862,any ideas where too find a schematic for it ,or one the same as i am sure this has other names,thanks (see pic)

author: jonpaul
author_rank: Super Contributor
timestamp: September 26, 2022, 04:06:49 am
content: One of thousands of Chinese knockoffs PSU.only the MANUFACTURER, no other sources of schematicSuggest that you open up, look for obvious damaged components, and actually fix it.The power circuit should be easy to trace out.j

author: golden_labels
author_rank: Super Contributor
timestamp: September 26, 2022, 04:38:30 am
content: As with many Chinese no-names, search for models that have “3010” in the name and the same front panel. Twintex TP-3010 for example.Inside I would not expect anything other than the simplest LM317 or jellybean op-amp controlled circuit.

author: Gyro
author_rank: Super Contributor
timestamp: September 26, 2022, 08:05:51 am
content: Looking at the photo, it actually appears to be a 10A output supply. In that case it is possibly an SMPS design [Edit: although the large case size might hopefully indicate linear].Repair might be simple but fault finding will involve more shock hazard due to the much larger proportion of mains side circuitry. I agree, internal photos are needed.

author: tekguy
author_rank: Contributor
timestamp: September 26, 2022, 02:27:12 pm
content: sorry my bad,its a 10a linear,when i got ot only one pair of pass transistors were getting drive,4 power diodes were open also 4 4007 diodes open,i replaced those and now i get 0 output,theres is a 555 controling a relay that shouls latch,seems thats dead,its like the output wont turn on,it did output power with the 2 pass transistors not beeing driven but was 5a max.

author: simba15
author_rank: Regular Contributor
timestamp: September 26, 2022, 03:43:17 pm
content: I also just acquired one of these but a Dual output version,Unfortunately there seems there are lots of these around but with many different model #s its hard to know what the correct schematic is. (Mine is a MPS3003-L)I think i found one that is correct for my device but it is a damn scribd link so i cant get further than the first pages.https://www.scribd.com/document/431668440/Matrix-MPS-3003-5L-3-DC-Power-Supply-ManualMine has a Output cap that may have blown (but in circuit test shows not shorted).Pics to follow.

author: Gyro
author_rank: Super Contributor
timestamp: September 26, 2022, 04:37:27 pm
content: Quote from: tekguy on September 26, 2022, 02:27:12 pmThose are RF power transistors!Surely they can't be original fitment? I'm confused.It looks as if somebody has DIY'd it, I think we need internal photos as it probably doesn't correspond to any of the off-the shelf ones.

author: golden_labels
author_rank: Super Contributor
timestamp: September 26, 2022, 05:41:55 pm
content: Quote from: simba15 on September 26, 2022, 03:43:17 pmIt seems the Matrix version of OP’s PSU is MPS-3010l-1.Quote from: tekguy on September 26, 2022, 02:27:12 pmSlowly, please. Both from your attempted repair and how you write I get a feeling of doing everything extremely hastily. To me it’s almost impossible to even understand, what you want to say. The photos don’t show much.Do not rush, do not randomly replace elements. Eight diodes being short sounds weird. I am not saying it’s impossible, but it would be very rare and indicate some major catastrophic failure. Whatever caused the diodes to release magic smoke is still there and will likely kill new ones too. The culprit should be identified. You did not mention the fuse too. If there was a short, no to mention a short of magnitude sufficient to instantly nuke eight elements, and fuse would not act, you would be holding a molten blob of plastic.Work step by step. Try to understand the overall construction of the PSU and then ensure, without powering it on, there is no unintended shorts. Take photos of the inside: but please do it with proper light, possibly from a desk lamp. If your camera can’t focus, try from bigger distance. We can deal with poorer resolution, but not with blurred, overexposed images.

author: factory
author_rank: Super Contributor
timestamp: September 26, 2022, 05:44:51 pm
content: Fairly certain it's the exact same PSU in this thread from a banned user, the transistors were stated to be TIP3055.https://www.eevblog.com/forum/repair/skytronic-650-682-0-30v-0-10a-psu-repair/msg4132639/#msg4132639David

author: tekguy
author_rank: Contributor
timestamp: September 29, 2022, 03:26:03 am
content: Sorry about the transistor pics,not sure what happened there!,brain fart lol.

author: Halcyon
author_rank: Unknown
timestamp: September 29, 2022, 04:06:00 am
content: tekguy, care to reply to my PM the other day?

author: tekguy
author_rank: Contributor
timestamp: September 29, 2022, 08:12:26 am
content: here is a pic of the problem board,the 555 is on the right,also all the transistors in that are have been replaced,ie the signal transistors and the to 220 pair.