Hard Drive Power Supplies

[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.

[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).

[goontron]

Re: Hard Drive Power Supplies

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

[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

[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

^ no.

[CapLeaker]

Re: Hard Drive Power Supplies

Did the old diode test bad?

[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.

[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

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

[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

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

[kaboom]

Re: Hard Drive Power Supplies

Resolder the pins on the TX primary side, and also replace the diode feeding the cap for the PWM IC.

Don't check and assume it's good- they can get fussy til they warm up.

Back in the late 90's, I fixed two of those "Packard Bell" Pixie monitors.

+12 was missing for about 20 minutes after a cold start and supply was cycling. Degauss relay was powered by that same +12, so it would click too.

I fed +12 in from a seperate supply and it came to life. First I changed the cap- no change. Then I isolated that feed and checked for shorts. No shorts.

For testing, I replaced the schottkey with two 1N4004s. They got warm (hot?), but unit now worked.

All was well after a new TO-220 schottkey; cap was still OK.

[goontron]

Re: Hard Drive Power Supplies

No dice. still does it.

[goontron]

Re: Hard Drive Power Supplies

That's what I get for ass-u-me-ing..

that light green one has a black marking on the top. i put that there because it wasn't out of tolerance, but it was high, its graphite. It looks like its just doing filtering and with a rating of 1500uF i'm going to replace it with a 2200uF anyway. Lets see how it does with new low value caps!

[kaboom]

Re: Hard Drive Power Supplies

remember, this isnt one of those cheap units. Its an HP tape drives internal PSU. EGC is already bonded, has fuse, pi-filter, etc. i will look for bad soldering and replace that cap.
I have tested the output caps. one was bad, and i replaced it.

That's what I get for ass-u-me-ing..

[goontron]

Re: Hard Drive Power Supplies

10-22u, 50V, near the SMPS IC, likely a cheep submini electro. Probably right by the transformer. You can use anything from 10-47u, 50V. It's quite possible that the aux voltage is nowhere near that; a 25 or 35V cap could work, but either measure it or find out what voltage the SMPS IC clamps it at. Some have an interal shunt reg, that limits the voltage across that cap- it's fed thru a resistor after the aux rectifier/winding.

And if you're going to change the O/P caps, why not do a before-and-after scope 'n load test?

If you have a scope, that is...

I'm betting you've got well over a volt of ripple on +12, even at 1A. More if there's no pi-filter.

Don't forget to bond common to the EGC and rewire the AC input, putting the fuse in the hot, where it belongs.

remember, this isnt one of those cheap units. Its an HP tape drives internal PSU. EGC is already bonded, has fuse, pi-filter, etc. i will look for bad soldering and replace that cap.
I have tested the output caps. one was bad, and i replaced it.

[CapLeaker]

Re: Hard Drive Power Supplies

either a bad starting cap or bad solder joints. Some are really hard to find. Read this thread:https://www.badcaps.net/forum/showthread.php?t=47479
I finally found it with my hot air soldering station.
Norstar: 0
CapLeaker: 1

[stj]

Re: Hard Drive Power Supplies

maybe.
or bad solder joints.

[kaboom]

Re: Hard Drive Power Supplies

ok, mine developed an issue. it pulses on switch one then eventually starts. Thats a startup cap issue right?

10-22u, 50V, near the SMPS IC, likely a cheep submini electro. Probably right by the transformer. You can use anything from 10-47u, 50V. It's quite possible that the aux voltage is nowhere near that; a 25 or 35V cap could work, but either measure it or find out what voltage the SMPS IC clamps it at. Some have an interal shunt reg, that limits the voltage across that cap- it's fed thru a resistor after the aux rectifier/winding.

And if you're going to change the O/P caps, why not do a before-and-after scope 'n load test?

If you have a scope, that is...

I'm betting you've got well over a volt of ripple on +12, even at 1A. More if there's no pi-filter.

Don't forget to bond common to the EGC and rewire the AC input, putting the fuse in the hot, where it belongs.