HP DPS-340CB A - lots of smoke!

[everell]

I was just given a HP DPS-340CB A. Just the kind of challenging project I like! I wonder if it went BANG or just filled the room with smoke. Looks like a power supply with active PFC, and two separate pc boards. The main power fuse is blown. I figured the best starting point was to take some pictures and post them on the forum. I'm sure I will get lots of help and suggestions.

[370forlife]

Re: HP DPS-340CB A - lots of smoke!

Wow.

Those definitely look like the APFC coils that got roasted. Looks like they have two in series to fit into the smaller space. Interesting. Don't know how easy of a fix this will be.

Looks like it just did a smoke show, maybe one of those diodes blew out and made some noise. Might be why the coils got torched alive. I just noticed it looks like there are some remnants of something next to C13 that was attached to the heatsink.

[everell]

Re: HP DPS-340CB A - lots of smoke!

The two APFC transistors are shorted. They are Toshiba K2915 N channel MOSFET 600 volt 16 amp Rdson=0.4 ohm. Just looked on Mouser website - they are no longer available. I am thinking that perhaps a STW20NK50Z should work.

[c_hegge]

Re: HP DPS-340CB A - lots of smoke!

I've seen lots of PSUs go bang and/or fry themselves when the fan fails but I've seen anything like this before.

[370forlife]

Re: HP DPS-340CB A - lots of smoke!

FDP18N50's would probably work, digikey has them in stock, have a bit lower RDS(on) for better efficiency, a few cents cheaper and rated 1A higher. They are used in seasonic s12 II 520W's so quite well overbuilt for this 340W.

[momaka]

Re: HP DPS-340CB A - lots of smoke!

Never thought I would see a Delta power supply burned like that! Did the problem start from the primary side? If so, I wonder what caused it. Normally, you'd expect the PSU to shut down in situations like this.

[POM_MJ]

Re: HP DPS-340CB A - lots of smoke!

Wow, lot of smoke generated I think.

[kc8adu]

Re: HP DPS-340CB A - lots of smoke!

sure that wasnt a lightning strike?or at least initiated by one?

[Toasty]

Re: HP DPS-340CB A - lots of smoke!

Perhaps running off a non-sinusoidal UPS? Raises havoc with APFC, iirc. Can you get more history?

[everell]

Re: HP DPS-340CB A - lots of smoke!

Repair work has begun. First step is to clean up the larger of the two pc boards which has the main switching transistor and outputs. So alcohol and a brush - and lots of elbow grease, and the board cleaned up quite well. Four wires were burn damaged, so were spliced with new wire so that I could tell which wire is which by color code.

Next, I took an old junked AT power supply, and using the AC input, input filters, bridge rectifier, and main filter caps, wired the +320 volts to this pc board. With green wire not grounded, the 5vsb came up no problem. Then with green wire grounded, the output voltages came up no problem. Looks like all of the serious damage is on the other board.

[everell]

Re: HP DPS-340CB A - lots of smoke!

The other pc board has the input filters, bridge rectifier, APFC circuit, and main capacitor. The two coils in the APFC were burn damaged beyond use. One of the APFC FET transistors was shorted. And a filter capacitor across the bridge rectifer was damaged.

I have cleared most of the burned spot on the pc board. Will have to remove some more of the burned area. Then I can use epoxy to fill the hole area and have something to mount replacement coils to.

With the APFC transistors removed, I applied power to the board. The main capacitor charged to 170 volts. So the bridge rectifier, input filter, and main capacitor are OK. Big question is whether or not the APFC circuitry driving the two FETs is bad or not.

Pictures show the board repair so far, and damage to the filter capacitor across the bridge rectifier.

[c_hegge]

Re: HP DPS-340CB A - lots of smoke!

Toast marshmellows on it.

[everell]

Re: HP DPS-340CB A - lots of smoke!

For whatever the problem was with this power supply.......it burned the HELL out of any marshmellows! I just took the fan apart. Burned the HELL out of it too.......well done crispy parts inside along with black burnt coil windings. The fan will be ....replaced.

Look like the only real challenge will be repairing the APFC pc board.

[mur]

Re: HP DPS-340CB A - lots of smoke!

If you have a scope, you can test APFC control ic if you bring the supply voltage to vcc pin and check if you get any pulses on the mosfet drive pin(or output or whatever it's called).

[everell]

Re: HP DPS-340CB A - lots of smoke!

I will have to rewind the two burnt toroid coils. I found two sources for buying magnet wire. Has anyone had any dealings with these companies? Always nice to do business with someone having a good reputation. The companies are both at the same address with websites as follows:

www.bulkwire.com
www.powerwerx.com

[everell]

Re: HP DPS-340CB A - lots of smoke!

Well.....I ordered a 50 ft spool of 18AWG magnet wire from www.bulkwire.com Thursday. It arrived in my mail Monday afternoon. Good prices and good delivery time. So now I have rewound the two coils on two toroid cores from scrapped power supplies. Will have to dip them in varnish before mounting them to pc board.

I have also completed the repair on the burnt hole in the pc board. Just cleaned out the black stuff down to where I could find good board material. Then cut out a piece of perf-board slightly smaller than the hole. Then mixed some epoxy and filled between the two pieces. Photo attached.

And....for all you Abit KT7A lovers....here is my KT7A, loaded with Ubuntu 10.04. One of these days I am going to get a case for it!

[stj]

Re: HP DPS-340CB A - lots of smoke!

Question,
why magnet-wire?

i thought it was just enameled copper wire?

[everell]

Re: HP DPS-340CB A - lots of smoke!

In this country, the trade name is "magnet wire". It is just copper wire with insulation coating. Go to www.bulkwire.com and check out the specifications. It is just copper wire with two coats of some chemical - I believe it is more flexible than enamel coating which would flake off when the wire is bent.

The sum of the inductance of the two burnt coils was 895 uH. The sum of the inductance of the two new coils is 882 uH. Close enough for me. Winding a coil of 18 AWG wire on a toroid coil is somewhat difficult to get a tight wind. So I am looking for some varnish to finish the job and keep the winding in place.

[ChaoZ]

Re: HP DPS-340CB A - lots of smoke!

I am still using one of the older delta 300watt-ers. Cant wait to read your progress!

Impressive!

[everell]

Re: HP DPS-340CB A - lots of smoke!

Finished "surgery" on the badly damaged APFC circuit board. Installed the two new Fairchild FDA 18N50 FET transistors in the APFC circuit. Installed the two newly hand wound coils. Replaced the bad capacitor with .47 uF/630 volt. Now for the big test!

Powered up the psu with power-on switch off. 5vsb came up fine. Turned on power-on switch. All voltages came up great using one CDROM and one hard drive as load. The voltage across the main capacitor was 167 volts off and 403 volts on.

Photos attached to show final repair of the APFC board. More repair work than I usually like to do, but I enjoyed the challenge.