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Problem finally solved (Really this time!) & sonics...

Resolving the problem... FINALLY!

I was wrong. When I last posted, my issues with my linear supply were not fixed. The computer would always turn off after running awhile... It might cut out in as little as 30 minutes, it might run as long as 8-10 hours, but it would ALWAYS shut down at some point. Sometimes it would reboot... Mostly it would just turn off.

At first, I focused on the possibility of the regulators overheating and going into thermal protection shutdown (unlikely as the chips are rated for 125C and were only getting to 60C).

I tried the following:

1. Installed separate small heatsinks for the ATX 12v and 3.3v regulators to reduce their temps.

2. Changed the regulator biasing scheme. I configured my regulators based on this thread by John Bau, the designer of Spica speakers, where he worked to optimize the performance of 317/337 type regulators: http://www.diyaudio.com/forums/power-supplies/143539-another-look-lm317-lm337-regulators-5.html#post1891710 . When I setup my linear-hybrid power supply last year, I used the optimization scheme he published in the first few posts of the thread. When I configured this fully linear supply, I used his final optimization scheme, which seemed to set a higher current level for the internal amplifier of the regulator chip, possibly promoting thermal protection shutdown. So I went back to the earlier scheme.

3. Changed out all the regulator chips to ensure I didn't have any defective ones.

4. Change out all the rectifier diodes (a longshot, as failing rectifiers just fail in my experience, they don't go intermittent).

None of these prevented the eventual shutdown.

I then focused on the controlling voltages. When I first configured the supply, I found that the motherboard would run ok after booting if you turned off the 5vSB, PWR_OK, and -12 lines, so I used one 9v battery regulated down to 5v for the 5vSB & PWR_OK lines and two 9v batteries in series regulated down to provide the -12v. And after the motherboard was running, I turned them off to prevent running the batteries down. I later tried a single un-regulated 9v battery (Thanks Gene!) for the -12v and that worked just as well as the regulated -12v, so I left it that way. But all the while using this control voltages scheme, it still turned off eventually.

After playing around with this, I found that the 5vSB and PWR_OK being off were causing the turn-offs. As long as these voltages were provided, it would not turn-off. But cut them off and the board would run at first, but eventually shut down. So I've installed an additional small linear supply to provide 5v for the PWR_OK and 5vSB. I now only turn off the -12v (still provided by a 9v battery) after the motherboard is running.

Now it stays on all the time!

Sonics?

It is still in the midst of component break-in (especially with the Black Gates), but initial indications are that it is a nice upgrade from the Linear/Hybrid supply with a modified PicoPSU, most noticably with greater definition at both frequency extremes, greater extension in the highs, and an increase in apparent dynamics. Interestingly, it is not nearly as large of an upgrade over the Linear/Hybrid as that was over the stock or modified Antec. Based on this, I'd still recommend the Linear/Hybrid as a viable alterative for those who want a very significant sound quality improvement with less work, cost, and hassle than the fully linear supply. But if you want the ultimate, the fully linear supply is the entry point.


Next stages?

Of course I can't leave well-enough alone. I've already gone back to the final regulator configuration from John Bau's thread and changed out the voltage-setting resistor bypass capacitors from Elna Silmec to Black Gate standards. (BTW, there is an interesting aside here... The diffences in sound quality of the Silmecs the Black Gates came through very clearly in my system, even though this is a non-critical component position in the power supply of the computer, not the sound card, DAC, or ancilliaries! I personally prefer the Black Gates with an overall greater sense of flow, a more palpable midrange, and ultimately a smoother and more musical sound, but many would prefer the Silmecs with a more dynamic sounding bass and a bit more 'technocolor' outlining of the sound. I do need to try the Nichicon Muse and Fine Gold caps here along with Oscons, Mundorfs, Sikorels, and Jensens as the Black Gate supply is dwindling fast! But my question for those who understand this better than I is why can component selections be clearly heard even though this is not in the 'audio' path?).

In the search for further sonic upgrades and operational improvements, next things to try are:

1. Feed the 5v for the 5vSB & PWR_OK from the main 5v supply instead of a separate supply. Simplified grounding and reducing the transformer and rectifier count may make this worthwhile.

2. Various regulator upgrades. I have the Linear Tech LT3080's here to try (Thanks for pointing out the comment in the K&K Audio DAC info, Rick!). They are limited to 1.1A which will work for the ATX 3.3v/12v and P4 12v, but not for the ATX 5v... But the chips can be paralleled for greater current handling and I'll use four to supply the 2.2A for the ATX 5v, one connected to each pin on the ATX connector.

Beyond these monolithic regulators, I'd like to try the AMB Sigma 11 discreet regulators (http://www.amb.org/audio/sigma11/), the high-current version of the Salas Simple Shunt (http://www.diyaudio.com/forums/power-supplies/143693-simplistic-salas-low-voltage-shunt-regulator.html and http://www.diyaudio.com/forums/power-supplies/168631-5v-high-current-low-noise-regulator.html, and of course Paul Hynes highly-regarded regs.

3. Low-noise raw DC supplies ala' John Swenson's design published elsewhere in this forum. While I used good-quality soft-recovery diodes and filtering caps, I suspect John's choke-filtered design will do a better job of minimizing supply-produced noise. But implementing these will require re-packaging and my supply will then no longer fit in the Zalman case, so it's a bit down the road.

4. Powering the P4 supply from my 'dirty' AC circuit. This is easy, I can use the old Linear/Hybrid to power the P4 and keep the fully linear ATX powering the rest of the computer. I'm very curious what effect this will have.

5. Getting the supply to work with the Dual-Bios motherboards such as the newly recommended GA-H55M-UD2H. I've been unable to get this simple (single switch to activate PWR_OK, no relays, no PicoPSU) linear supply to work with the GA-G31M-UD2H board and figure it won't work with any of the newer dual-bios boards. JackWong, have you tried the simple scheme with one of these boards with any success?

I expect that using a PicoPSU connected to the 5vSB, PWR_OK, and PS_ON# connections and controlling a relay that turns on the AC connections for the linear ATX 3.3v, 5v, 12v, and P4 12v will provide the sequencing needed for the dual-bios boards. My gut feel is that it MAY take a slight delay on the PWR_OK signal (to allow the linear supplies to power-up), but that's a simple circuit to implement (555 timer and a relay on the PWR_OK line). I'll give that a try soon.

6. Batteries (someday!).


Enough for now, I'll post again soon with my thoughts on how-to's.

Greg in Mississippi

P.S. Current usage is getting down there due to the slightly lower voltage, with the ATX 5v @ 2.2A, 3.3v @ .3A, 12v @ .1A, and the P4 at .5A, giving just over 19w!
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  • Problem finally solved (Really this time!) & sonics... - GStew 12:49:12 07/08/10 (0)
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