Power Supply POP! Why?

[alec_t]

Agreed. The power cycling knocks that potential problem on the head.

 

[cowboybob]

... (does it matter that DC is isolated from ground on the upper ...

Most assuredly YES. The output of the HP DPS-1200FB you're using has it's PCB and output negative terminal at case ground (all the way back to the ground terminal at the mains power plug).

Since the two supplies, in series, might be stacked one on top of the other, and the "upper" PS does not have it's ground leg floating, it will short out the "lower" PS.

...any problems using this as 12v if isolated?).

No and Maybe.
Certainly not if used as 1/2 of a 24VDC source.
Maybe. Let the buyer(s) know which PS (of the pair) has its ground floating. I would think that then it's their responsiblity to decide if it should be used for their single 12VDC purpose(s) or not.

 

[jocanon]

Thanks cowboybob, just to clear up the misunderstanding though, my question was does it matter that it is isolated from ground with regard to using it as a stand alone 12v supply. In other words, the first part of the question cannot be separated from the second, it was not two questions but only 1 question. I know you have to isolate one in order to connect the 2 in series, I have done it hundreds of times. Maybe a better way to state my question is: Since the upper one is isolated, can it be used as a stand alone 12v supply even though it is isolated from ground? Sorry for the poor wording on my part. You answered my question in the last part of your post...any other opions, insights from anyone else? What are the problems with using it as a standalone 12v supply when it is floating?

 

[coolice]

Hey.

The DPS-1200 use the metal casing as a heat sink, hence the small form factor of this PSU. There is a thermal conductive pad in the plastic sheath that connects the smaller internal heat sink to the case.

Ian

 

[KeepItSimpleStupid]

One power supply I have called "A fixed voltage power supply, selectable between 0-32 V" 10 A. Why selectable, you need to move some transformer taps.

It does have an interesting form of short circuit protection. Current goes to 10 A, voltage drops to nearly zero. No real sparks.

It's a linear supply and after I bought it I tested it with an auto headlamp. Pop, voltage increased and the pop again - more increase. It used about 10 2n3055 type transistors as a linear regulator. three transistors were the wrongs ones.

 

[Rc Poweer]

Can someone please help me ASAP... everyone is using the 1200FB power supply but I really want to use the Lite ON Dell PS-2112 but I dont know the pins to jump etc.. can someone please help me get this unit working

 

[Tony Stewart]

My guess is that you did not supply the required forced air at the maximum power load and either a lid on a Cap popped or a MOSFET shorted and a crater formed on the surface of the epoxy from the explosive outgassing.

18A*12V=216W will need at least 1m/s air speed thru the box as there is no visible fan.

WHen I had a design like this, I epoxied a thermistor to the hottest part and regulated two 1.5" fans so the hot spot would never exceed 60'C, which meant the fans were off up to 30% max power, then start slowly, with increased load.