Upgrading the Supremo
First I tried to see what can be done with the −12 V rail voltage so I started with hooking two-diode rectifier (both diodes connected in parallel) instead of the original DO-package diode. The goal was to try lowering the voltage drop and give the regulator slightly higher voltage to work with. I could have placed different rectifier on the stand-by rail to increase the loss, but that would lower the efficiency so I let it be.
In its previous shape (filled with Taiwanese crapacitors) I could not offer this thing for sale, besides, the ripple was not as low as it could be (compared to the Silverstone Strider). So I got the opportunity to use something of high quality and see what happens. Unfortunately I could not use anything better on the +3.3 and +5 V rails because there are polymers with almost the highest possible capacity and I do not have anything better.
I have also been thinking what to put on the +12 V rail in usual D10 size. The possibilities were custom Samxon RS 3300 uF/16 V and custom Nippon Chemi-Con KZN 3300/16 D10×40 mm. The former has higher capacity and slightly higher ESR, the latter has higher capacity and much lower ESR. So I consulted the Strider for advice, it shares the same platform and has quality caps: Chemi-Cons KZE, also with very low ESR. So I opted for KZN 3300/16. Smaller D8 caps were mostly replaced with Chemi-Cons KZH 1000/16 or KZN 1500/6.3.
The last thing was to at least partially fill the blank spots, which in the Strider’s case were all used. So I at least added two small 100 ohm SMD resistors on the stand-by rail (which will affect the voltage by maybe 10 mV). Two Rubycon YXJ 220/25 caps were placed into vacant spots for PCIe cables on the modular board. Also most of the spots for SMD capacitors have been filled with caps from old dead graphics from my junk pile. Plus the spots on the main board were filled. That added couple tens of microfarads and the possibility to filter high-frequency noise.
So after couple hours of work and my back starting to hurt I packed everything up and wanted to try the unit. The first try resulted in some popping and smoke but the only problem I found was some colophony dirt on a single SMD diode. Maybe higher voltage appeared there and the colophony burned a little. Nothing else anywhere, after cleaning it the Supremo M1 Gold 550 W worked again but I let it be for a few days to be sure. After that I put it together again and connected to my loader, than it worked without troubles. The voltage on the −12 V rail increased rather than the other way around which indicates the problem to be on the common secondary coil rather than the main transformer winding.
But the results are not that bad, with approx. 100% load the ripple results are slightly better on the +5V rails and about the same on +3.3 V rail (with some measurement error).
The −12 V rail got worse, as the voltage actually increased even more the regulator is not regulating at all so the voltage just passed, together with the ripple which increased little bit. In any case the unit now has quality capacitors capable of surviving at least five years. Plus the ripple on the most important rails went down a little bit so overall I think it is success.
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