Hard Drive Power Supplies

[goontron]

Re: Hard Drive Power Supplies

^what looks like the primary switcher has 6 legs. is that the SMP ic?

[kaboom]

Re: Hard Drive Power Supplies

^what looks like the primary switcher has 6 legs. is that the SMP ic?

Yep. Common in certain DVD/BD players too.

It's sort of like a giant TOPswitch. Can't give a more specific example w/o the P/N of that IC...

There should be a large resistor from B+ to one of those small caps on the pri side. That same cap will have a diode, possibly thru a low-value resistor, from a transformer pin- the aux voltage for the PWM IC.

This one charges that cap via internal bypass until supply "kickstarts." Yours might do the same if you can't find that resistor.

Also notice that D5 is a 1N4007. They don't want the snubber diode to be too fast, since it could lead to excess RFI.

[goontron]

Re: Hard Drive Power Supplies

^fixed the startup, but now the tranny makes a chattering sound.

[kaboom]

Re: Hard Drive Power Supplies

^fixed the startup, but now the tranny makes a chattering sound.

What did you replace?

[goontron]

Re: Hard Drive Power Supplies

a diode that has "er106" written on it. in between the the opto-isolators and that larger of the two caps on the primary.
actually, it still pulses on startup.

[CapLeaker]

Re: Hard Drive Power Supplies

Did the old diode test bad?

[goontron]

Re: Hard Drive Power Supplies

^ no.

[kaboom]

Re: Hard Drive Power Supplies

What is that PWM IC?

I'm assuming (again, lol) that it still pulses with heavy loads on the outputs.

[goontron]

Re: Hard Drive Power Supplies

^ pulses on startup with load.
makes a Thunking/chattering/fast tick noise out of the trafo with no load when running.
TOP247YN

[goontron]

Re: Hard Drive Power Supplies

DOH! i changed the 220uF cap next to the opto-couplers with a 330uF. no wonder its oscillating.

[mockingbird]

Re: Hard Drive Power Supplies

Just a heads up, there have been HDDs spotted in the wild that require 3.3V.

So the ideal HDD adapter would have 12v, 5v, and 3.3v, and two connectors, one SATA power, one molex.

Just a heads up...

Newer PSUs will (or should?) come with a four wire SATA power connector instead of the usual 5.

Pin 3, which was formerly used for 3.3V is now being used to signal power disable, which allows a hard-reset of the HDD through software (convenient for data centres which need to remote control HDDs apparently).

[momaka]

Re: Hard Drive Power Supplies

^ Interesting. I wonder if that signal is just a matter of simply pulling the pin High/Low.
Probably pull low (with the HDDs having an internal pull-up resistor to 3.3V) to disable the HDD so that such HDD would still work when connected to a PSU that has the 3.3V wire. But that's just my guess, of course.