Power Supply Strengthening
I recently got a second hand EVGA 500-W1 power supply to replace a power supply I did not trust only to discover that the EVGA 500-W1 has a design flaw as discovered when being reviewed
It failed under load because the bridge rectifier it uses is only rated for 3A without a heatsink while a 500W power supply of 80% efficiency at 115V will take almost 6A,
so it is no surprise that it died despite the fan cooling; this was likely done intentionally as a hot rectifier has less losses.
The great thing about this particular power supply is that the board has a place for a second bridge rectifier and so the fix is easy, namely to install two bridge rectifiers in parallel.
Rather than use the original bridge, I opted to have a matched pair.
Now it might be argued that the modification is not as good as might at first seem since the diode drop losses mean that the overall heating hasn’t changed much and that the cooling by fan isn’t that different from before, but I still found this modification satisfying, perhaps because the thermal contact with the board was improved, there now being eight legs rather than just four. If needed there is a 2mm gap between the two bridges to mount a heatsink.
Not so much a repair (the supply was working), but a modification to avoid future failure.
This article was written by Anwar (Andy) Shiekh originally from London, England; he repairs things to help make an income go further and presently teaches Physics in Colorado, U.S.A.
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Note: You can check his previous repair article on USB C TO A Connector
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Tayo
July 20, 2024 at 12:32 pm
Strange they designed the board with a spot for a 2nd BR....
I would try to figure a way to stress test this before putting into service though.
Interesting fix.
Anwar Yunas Shiekh
July 20, 2024 at 8:54 pm
There is also a 430W, 500W and 600W version of this supply, probably all using the same board.
Albert van Bemmelen
July 20, 2024 at 1:39 pm
That was a quite unexpected but interesting fix! Although I wouldn't risk burning a blu-ray or a dvd on computer with a maybe still questionable 500 Watt power supply?
Yogesh Panchal
July 20, 2024 at 3:44 pm
I Have seen in many circuits they marked Components but physically there is no component Installed, May be having some reason....Research & Development always increases our knowledge.( May be at some additional cost in terms of damage).
all the best...
Parasuraman S
July 20, 2024 at 6:10 pm
That was very interesting to read! The first time I heard about two bridge rectifiers fitting in parallel! News to me! Thanks for sharing!
Mark J
July 21, 2024 at 3:47 am
In my repairs I have not encountered bridge rectifiers in that configuration. Maybe in the future I will.
Anwar Yunas Shiekh
July 22, 2024 at 12:26 am
Just noticed this repair of a 450W supply for 220V only
https://www.youtube.com/watch?v=UsKezf-OtDY&t=4s
However, the rectifiers look like 1A units which would explain why they failed.
Waleed Rishmawi
July 22, 2024 at 2:42 pm
any interesting modification and very satisfying to do. thanks for sharing and have a blessed day
tony
July 23, 2024 at 4:37 pm
never a good idea to put diode in parallel. the one with lower forward voltage is the one that conduct . better to put a bridge with hig amps.
Anwar Yunas Shiekh
July 24, 2024 at 2:37 am
A most valid point, but then one wonders why the board has room for two; in this application the limiting issue is cooling and not current and I used a matched pair.
Humberto
August 19, 2024 at 11:56 pm
Good repair. I really enjoyed reading your article.