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| Schematics for Delta PSU |
Posted by: bibilit on 2021-11-27 01:42:56
Looking for a Delta SMP-120EB PSU schematics
pretty sure a Zener diode at least is bad.
Found on Quadra and Centris units. |
Posted by: mmu_man on 2021-11-27 03:02:47
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? |
Posted by: bibilit on 2021-11-27 09:54:55
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. |
Posted by: joshc on 2021-11-27 10:57:32
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. |
Posted by: mmu_man on 2021-11-27 12:06:42
There should be a reference on the zener, and datasheet for them detailing which reference corresponds to which voltage. |
Posted by: mmu_man on 2021-11-27 12:12:30
Ah, my Quadra 650 has the same PSU, let's crack it open and see. |
Posted by: mmu_man on 2021-11-27 12:36:13
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. |
Posted by: mmu_man on 2021-11-27 13:22:34
The stuff around the Triac on the first board (the one with the fuse) is odd. I don't think it's PFC, those weren't a thing back them. It could be overvoltage protection, some use a zener to control a thyristor. |
Posted by: bibilit on 2021-11-28 08:07:59
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. |
Posted by: joshc on 2021-11-28 08:15:01
Nice job. Satisfying when you can get an original PSU working but recently I've been doing ATX conversions instead. |
Posted by: mmu_man on 2021-11-28 09:12:23
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… |
Posted by: joshc on 2021-11-28 18:18:55
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. |
Posted by: Jockelill on 2022-08-06 07:32:27
Reviving this old thread since I’m currently rebuilding a few of these PSUs. I’ve found that the fan can be replaced with a
Noctua NF-R8For a much more silent PSU. This fan fits directly to the connector on the circuit board (even though it only a 2 pin original and fan has a 3 pin connector).
This fan also fits a few other IIci PSUs. |
Posted by: olePigeon on 2022-08-06 16:15:12
By pure coincidence, Amazon has these on mad sale. 34% off, or $10 a fan.
I'm gonna get me a few. Thanks for the tip!
Edit: That's the 1200 rpm instead of 1800 rpm. Is it still good enough? |
Posted by: LaPorta on 2022-08-06 16:42:31
Thanks for the tip!` |
Posted by: Jockelill on 2022-08-07 05:29:01
By pure coincidence, Amazon has these on mad sale. 34% off, or $10 a fan.
I'm gonna get me a few. Thanks for the tip!
Edit: That's the 1200 rpm instead of 1800 rpm. Is it still good enough? Not sure actually, but 9dB instead of 17 (stock is about 30dB) is very tempting🙂. The 1800rpm works great in my IIcis and one is with Carrera accelerator and three Nubus cards. Would be interesting to make some tests with it. Like run the computer a few hours with stock, change to 1800rpm and then try the 1200rpm. One should measure the temperatures inside the chassis and also in the PSU. By coincidence I have all the equipment for this 😅😅. I’ll order some fans also and test. |
Posted by: olePigeon on 2022-08-07 07:48:22
I bought a Noctua NF-A8, but I don't know if it worked because either my power supply and/or my IIci died at that moment. |
Posted by: Jockelill on 2022-08-07 08:23:52
But isn’t a8 a 5V PWM controlled fan? You need a 12V fan for the IIci🙂 |
Posted by: SuperSVGA on 2022-08-07 09:17:21
But isn’t a8 a 5V PWM controlled fan? You need a 12V fan for the IIci🙂 The A8 comes in both 12V and 5V, though I'd say the 5V is rarer/more difficult to buy accidentally. |
Posted by: olePigeon on 2022-08-07 21:12:57
I have the 12v version. |
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