VOGONS


A tale of two PSUs

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Reply 460 of 472, by RacoonRider

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canthearu wrote on 2020-03-02, 10:46:

In theory it doesn't matter.

In practice, bridge rectifiers use typically bigger diodes internally and the form factor allows for better heat dissipation and more current carrying than using general purpose diodes in a bridge configuration.

Using discrete diodes instead of a single component bridge rectifier is a cost cutting measure typically. Doesn't automatically mean the PSU is a dangerous misrated gutless wonder, but it normally isn't a good sign.

I'm not sure that's exactly the case.

Using the exact same diodes instead of a rectifier initially costs more. It requires a slightly more complex PCB and extra soldering points. The bridge chip should cost less than the exact same diodes packed in DO-41. And separate diodes should dissipate heat better! Remember that they have much more surface than a bridge chip, are at distance from each other and work only 50% of time.

However (I admit this is more of a speculation, correct me if I'm wrong), if you buy cheap diodes with high voltage drop, they will easily compensate for the initial drawback in cost. Higher voltage drop means more heat, so they will probably get hotter than a bridge package. And since you are already cutting costs, why not get diodes rated for a lower current? Now, this is a recipe for disaster.

Reply 461 of 472, by SirNickity

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I agree with you, but I think the point is that there's a common correlation between using discrete diodes and manufacturers that build junk PSUs. All of the brands of PSUs I use, that I trust my retro PCs' lives with, use a single bridge rectifier component. *SOME* of the garbage PSUs that I've opened up and subsequently decided to install in the garabge can used discrete diodes.

It's not a factor, it's just a trend.

Reply 462 of 472, by Killian

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I opened up two AT power supplies, here are the pictures for archival purposes. Both are 200W, but the right one looks like better quality (better heat sinks, more components, ferrite core on the power switch cable, ...), although the solder on the monitor power connector looks a bit dangerous and ugly.
I am not an electrical engineer. Is there something interesting that you can see in those two AT power supplies?

Left: Codegen Model 200B (200W)
Right: EVER SPI-200G (200W)

8uRuphG.jpg

Reply 463 of 472, by wave

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The codegen should be used only for parts. It has absolutely no input filtering, this means that the EMI/RFI noise coming from the mains will pass on the output voltages and could cause issues with the computer operation, especially the sound card and the opposite, any electrical noise caused from the switching of the smps would pass to the mains and cause interference to other devices, especially critical to AM/FM tuners and audio devices in general.

Reply 464 of 472, by gdjacobs

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wave wrote on 2020-07-25, 11:43:

The codegen should be used only for parts. It has absolutely no input filtering, this means that the EMI/RFI noise coming from the mains will pass on the output voltages and could cause issues with the computer operation, especially the sound card and the opposite, any electrical noise caused from the switching of the smps would pass to the mains and cause interference to other devices, especially critical to AM/FM tuners and audio devices in general.

Couldn't have said it better. The Codegen also appears to have less effective output filters (LC instead of pi or T filters) and aluminum heat sinks which are more an afterthought than anything.

All hail the Great Capacitor Brand Finder

Reply 465 of 472, by drosse1meyer

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Hopefully this thread is still active, if more appropriate I can make a new one.

I'm working on restoring an older Dell p2/p3 machine (XPS R400) which requires a proprietary PSU. From what I understand, these MUST be non-PFC, and also have a nonstandard 6-pin mobo connection, which can be fixed with an adapter from amazon (https://www.amazon.com/dp/B0042GMAY2)

Obviously I want to be very careful and not to fry the board.

Anyway I was thinking what the best route would be. Should I bite the bullet and get a used Dell part (09228C), which is only 200W? Or be a bit more flexible and buy the adapter from amazon, and try to find an appropriate non-PFC PSU (I'm think 300w should be fine)? I hear good things about used Delta PSUs on this forum but I'm not sure what would work best in this case.

I also have an existing thermaltake 400 w CPU which I *think* is non-PFC (it has a voltage selector) which in theory would work with the aforementioned adapter. Pics attached.

So to summarize the options:

  1. Use the thermaltake I already have, but with the wiring adapter/harness
  2. Buy a used PSU (e.g. a delta) and use an adapter - how do I know its non-PFC??
  3. Buy the used proprietary Dell psu (which is only 200w)

Thanks for reading!

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P1: Packard Bell - 233 MMX, Voodoo1, 64 MB, ALS100+
P2-V2: Dell Dimension - 400 Mhz, Voodoo2, 256 MB
P!!! Custom: 1 Ghz, GeForce2 Pro/64MB, 384 MB

Reply 466 of 472, by pentiumspeed

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What PFC have to do with this? The PFC part is in AC input circuit before the actual hot side part of SMPS. PFC is to do power factor correction to bring reactive current and passive resistance waveforms into alignment so power utility's point of view losses is less. It is required to include this in PSUs for 80 plus certification.

Just don't worry about PFC, what you need is to make a DELL specific pinout using a terminal extractor and re-pin the ATX connector and add cables from PSU by soldering into PSU's circuit's 3.3V for extra 3.3V and ground 6pin connector.

Cheers,

Great Northern aka Canada.

Reply 467 of 472, by ChrisR3tro

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Hey guys,

I've got two AT PSUs. Both are in working condition, but which one would be the best and safest option for my new 386 system?

I suspect the EVER-branded one is of higher quality.

Thanks

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Reply 468 of 472, by mockingbird

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ChrisR3tro wrote on 2022-06-28, 17:20:

I suspect the EVER-branded one is of higher quality.

Without a doubt... Consider replacing all the electrolytics... They are now at least 20+ years old, if not closer to 30.

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(Decommissioned:)
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Reply 469 of 472, by DAVE86

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ChrisR3tro wrote on 2022-06-28, 17:20:

I suspect the EVER-branded one is of higher quality.

The OCTANE/OCTEK doesn't have proper, full input EMI filtering. Just one X2 pp film capacitor at C31. The fan control circuit might also be 'cost saved' or not implemented at all.
Total output power is around 140Watt. Sigle transistor controlled with what looks like 3842 pwm ic. 33 size center tapped main transformer. This unit won't go above 150W . Protection functions are done by a LM339 and some other transistors logic on the secondary.

The EVER/ProPower is just so much stronger and better in some ways... minus the original fuhjyyu capacitors.

Reply 470 of 472, by ChrisR3tro

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Thanks for your input, I suspected the EVER to be a bit better. What do you think about the caps? Should I replace them if possible or just check all the voltages and if they're ok, is it safe to use?

Reply 471 of 472, by DAVE86

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Measure the voltages under load and see if theres any fluctuation or anomaly. If your 386 gets unstable, freezes, randomly restarts, hdd starts clicking you should consider inspecting the power unit. Those fuhjyyu brand capacitors could be anything from ok to developing some internal short and blowing up 1 minute later...