Fan running, board not working

[joshage1]

I recently recapped a 2 DYNAMO (made in China / ATX Dynamo-350) Power Supply. When I connected a pin to green & black wire, the fan start rotating. Then I connected it to the motherboard, but when I press power buttun PS fan is running but thereis no power on the board.

1st PS.
I replace it also with Taiwan made caps with same rating, size, height, etc. Did not test ESR (No ESR meter). No problem with board since it is running now with good known working PS.

2nd PS.
I replaced it with Rubycon caps with same rating, but bigger and taller caps. Same problem....

What did I miss? Help...

[gastorgrab]

Re: Fan running, board not working

Clear CMOS?

[joshage1]

Re: Fan running, board not working

It's working on a known good Power Supply, so there is no problem with the board.

[dood]

Re: Fan running, board not working

Did the PSU's work prior to recapping? If not, they may be destined for the scrap.

[linuxguru]

Re: Fan running, board not working

PSU fan usually runs on +12v, so it seems to indicate that +5Vsb, PS_ON and +12v are all functional. That leaves +5 and +3.3 as key suspects. Connect the PSU to the mobo, press the power button and check all the rail voltages - +/- 5v, 3.3v, +/- 12v with the PSU fan running.

Did the board work with this PSU earlier, before recapping?

[joshage1]

Re: Fan running, board not working

Yes, it worked before, but them it has random system crashes or freezes sometimes. So, I checked the memory on another board and it worked fine. I check the video on another board it worked fine also. I checked the board for bad caps or burnt fets but didn't find any visual problem and so I opened up the PSU only to find out bulging Taiwan made caps. This China made DYNAMO already served me for more than year for 8 hrs or so a day . So I bought a new one in replace for it (400Php or 8USD). So the computer is now running.

Since I'm learning to recap here at "badcaps", I bought caps from our local store (some Rubycons and some Tayeh and Tung - just bought it since its hard to find rubycons, sanyo or nichicon of smaller caps on our local store)

I already have piles of PSU trashes here (all china made). 2 of them are Dynamo with the same problem, Bulging caps.

I recapped #1 PSU with all Taiwan made caps i bought, fan running but board not working, I guess linuxguru is right 12v ok but other voltages not. Better I should test it. but why? I recapped it with same rating, size, height, etc. and also of Taiwan made caps.

#2 PSU I recapped with Rubycons bigger in diameter but with all same rating but also same problem. What did I miss?

Sorry got no pics to take, cam too blur to take.

This is just experimental and educational and for study purpose why Im recapping those 2 Dynamo PSU. Anyway I bought a new one and using it for 8 hrs/day in a year wouldn't be bad for an $8 PSU.

Anyway, thanks for all your time.

[999999999]

Re: Fan running, board not working

I don't know what the build is like on these PSU, but I would suspect they dont' have enough capacity to start the system, or the 5VSB rail is flaky.

I don't think we can agree 12V rail is necessarily ok but not the others, "yet". We don't even know if 12V rail is at 12.0V (or close, when loaded by system instead of just a fan), and the PSU regulator IC should certainly be shutting it down if at least 5V rail isn't reasonable.

I have to disagree that it is a bad idea to buy an $8 PSU because the last one managed to run 8hrs/day and one year. Newer systems often have higher loads on a PSU and when a junk PSU fails it may damage the system, as well as stressing that system the whole time. To put it another way, you paid $8 a year then the time, trouble, shipping or delivery costs to replace these which over 4 years is at least worth $40, probably over $100 and even thousands of dollars loss in some business uses, but for the same $40 you could have bought a better PSU that takes up none of your time and poses the least risk to the system.

[linuxguru]

Re: Fan running, board not working

> Anyway I bought a new one and using it for 8 hrs/day in a year wouldn't be bad for an $8 PSU.

You're just ensuring another failure a year down the line. Have you considered the cost of reduced reliability on your hard disk, etc.? What's the cost of lost data as a result of a HDD crash?

You will do better to recap the new $8 PSU first, with good caps, before putting it in your system. That way, it might last for 3 years instead of 1 year, and reduce the risk of a crashed hard disk.

Even better is to get hold of a new/surplus $20 230W Delta PSU, which actually puts out about twice as much power as your $8 350W DYNAMO-ATX. It will probably last for 10 years and cause no damage to your HDD/mobo/CPU/RAM/video-card etc. in that period.

>What did I miss?

Probably lots of things. Undersized rectifier on +12v, caps on +5Vsb, small cap on the primary side near auxilary transformer, etc. Most importantly, all caps on the secondary must be low-ESR, long endurance, high ripple-current capable. Putting GP 85c caps, even Rubycon, may not suffice.