• Hello, Guest! Welcome back, and be sure to check out this post for more info about the recent service interruption and migration.

Schematics for Delta PSU

bibilit

Well-known member
Looking for a Delta SMP-120EB PSU schematics

pretty sure a Zener diode at least is bad.

Found on Quadra and Centris units.
 

Attachments

  • 66F8E256-1D7D-4BDC-8459-48B4C02A19EB.jpeg
    66F8E256-1D7D-4BDC-8459-48B4C02A19EB.jpeg
    1.8 MB · Views: 15

mmu_man

Well-known member
Quite unlikely you'll find this. However, most switching power supplies follow common designs, and if you look up the ICs reference you might find reference designs in the datasheet or application notes that are close to it.
As for zener diodes, you can usually test them in-circuit with the multimeter in continuity mode : as regular diodes they'll pass one way, and not the other way, since the zener threshold isn't met for it to pass in the other way. Testing the actual zener voltage wouldn't add more I think, usually they just fail completely, either break or pass always.
Sure the capacitors are ok in there?
What's the symptoms?
 

bibilit

Well-known member
Symptoms, dead PSU, was given to me with a bad fuse and shorted mosfet.
Replaced the Mosfet but the Zener is shorted.
Would like to replace, but don’t know the voltage value.
 

joshc

Well-known member
What is the diode connected to? Is it on the high or low voltage side of the PSU? That might give a clue of the sort of voltage it should be rated for.
 

mmu_man

Well-known member
There should be a reference on the zener, and datasheet for them detailing which reference corresponds to which voltage.
 

mmu_man

Well-known member
You didn't specify which zener… but anyway they all seem to have whatever reference they have on the side facing the board so not very readable anyway.
I just noticed on mine R2 has its heatshrink tube is quite burnt.
 

bibilit

Well-known member
Issue solved, after removing and testing the zener (ZD1) and confirming it was shorted for good, i was able to read the tiny reference.
Was a 18V Zener diode, removed another diode nearby as well, still good but as the PSU was in pieces already…

I connected the PSU to a IIsi and it fired right away.
 

Attachments

  • B3624246-C179-4D65-BDCB-C9FEC2EA6D7A.jpeg
    B3624246-C179-4D65-BDCB-C9FEC2EA6D7A.jpeg
    1.6 MB · Views: 9
  • EA435DCB-6D30-46D4-B4A0-AA900F4FB0B4.jpeg
    EA435DCB-6D30-46D4-B4A0-AA900F4FB0B4.jpeg
    2 MB · Views: 9
  • 36E12341-06B1-4951-8350-4ED40D73E8E6.jpeg
    36E12341-06B1-4951-8350-4ED40D73E8E6.jpeg
    2 MB · Views: 10
  • AAF9F465-D640-478C-9D49-67DB347456BC.jpeg
    AAF9F465-D640-478C-9D49-67DB347456BC.jpeg
    1.9 MB · Views: 10

joshc

Well-known member
Nice job. Satisfying when you can get an original PSU working but recently I've been doing ATX conversions instead.
 

mmu_man

Well-known member
Great, so I can put mine back in one piece 🙃
Someday I should recap it maybe, and check this resistor which I think is quite burnt. I noticed someone posted the cap values elsewhere here.
At some point it'd be great to get scans of the PCBs and pictures to RE the schematics for further repairs…
 

joshc

Well-known member
Great, so I can put mine back in one piece
I really hate opening these units. That stupid two-board sandwich design and the fiddly enclosure is not great to work with. I am converting one to use an ATX PSU inside it and it's going to be a lot neater that way.
 
Top