12w Potrans I.T.E Power supply model no UP01281120

[Per Hansson]

A small ugly external PSU for my Dreambox 500S satellite receiver

The receiver started acting up; as soon as I watched a channel from the tuner it would lock up within 2 minutes, however when watching recorded stuff over the LAN there where no problems, so the PSU was kinda the last thing I checked, heck, even my friends Dreambox 500S which is a later revision ran fine with this PSU for hours on end...

Anyway, I finally found out that the main cap had failed. One of the legs came loose when I removed the bunge. I got infinite resistance when measuring it's ESR
Though it still looked nice internally, wet with electrolyte and all, it was just the leg that had burned off somehow, perhaps oxidation after getting damaged by a power spike or surge, I dunno...

The new cap is a nice Sanyo FXS 400v 47uF, about 4mm thicker than the previous POS Ltec crap...

[Rainbow]

Re: 30w Potrans I.T.E Power supply model no UP01281120

The original cap appears a bit bulged.

[kc8adu]

Re: 30w Potrans I.T.E Power supply model no UP01281120

dump those lelon/ltec too

[Per Hansson]

Re: 30w Potrans I.T.E Power supply model no UP01281120

The original cap appears a bit bulged.

It might have been, but very little in that case... Looks more in the photo than it actually was...

dump those lelon/ltec too

I was going to, but Elfa was out of stock on one of them so I let it be for now...

[freebs]

Re: 30w Potrans I.T.E Power supply model no UP01281120

How did you get the damn thing apart?
I have a dead one here as well, I'd like to fix it.

[PeteS in CA]

Re: 30w Potrans I.T.E Power supply model no UP01281120

Two guesses:

* Use your fingernail across the whole label to see if it covers a screw that holds the thing together;

* If you don't find a screw holding it together, the case may just snap together, in which case you'll have to summon the dexterity and courage to pry it open using a flat-bladed screw driver or a putty knife.

[Per Hansson]

Re: 30w Potrans I.T.E Power supply model no UP01281120

Was just opening up this PSU to check it's caps
They looked fine but I somehow killed the shitty PSU, if you can see it in the pic I dunno but the diode connects from the PCB to the heatsink, it came loose and I guess it kinda disliked that because when I used the shitty soldering iron my dad had at his house and then tried to power it on I just got like 0.5VDC from it...

So I took it home to solder it properly, did not help...
When I took it apart again to do some ESR tests and so on I first did what I always do; shorted the main 400v bulk capacitor

This time around I got a real nice bang and arc!
How long does it usually take for bleeder resistors to discharge the primary cap(s) of any general type PSU? (Like is there some law or design guide that says it must be discharged in X ammount of time?)

As for the PSU I'm already giving up on it, it's crap anyway, new one bought on Elfa, part no 69-688-21 will hopefully get early next week

[Per Hansson]

Re: 30w Potrans I.T.E Power supply model no UP01281120

My friends Dreambox started acting up
The green LED on the front of the Dreambox 500S flashed rapidly as soon as the PSU was connected

It had run fine up to this point and now had been left without power for a few hours, after this it would not work...

We ordered the PSU I mention above from Elfa, because this POS is anyway underpowered for the Dreambox (it draws ca 12w when you measure it so the thing must be close to 100% loaded...)

Anyway this was on a Thursday and we did not expect the new power adapter from Elfa untill Monday, so I made a little test, I put the thing in the owen at 60°C for 10 minutes
After this we took it out and tried again, it powered right back up, green LED permanently lit
Anyway, now that he got the new adapter I soldered out the capacitors and measured them, the two secondary caps has ok ESR and Capacitance, so has the primary cap (it is not low ESR tho)
What had failed was the two small caps, they have ok capacitance (ca 4.4 and 15 or so) however on the 22uF cap I can't even get a ESR reading, and on the 4.7uF cap I get an ESR reading of 96
Simply amazing
Oh, they are also general purpose caps, real intelligent design of this POS!

They also made a mistake on the label, it says "for indoor use only"
It should really say; "for target practice only!"

[momaka]

Re: 30w Potrans I.T.E Power supply model no UP01281120

What had failed was the two small caps, they have ok capacitance (ca 4.4 and 15 or so) however on the 22uF cap I can't even get a ESR reading, and on the 4.7uF cap I get an ESR reading of 96
Simply amazing

That's the same problem I had with a Shang Ming 5v power adapter for a D-Link router. Put it under the sun for 20 minutes (was summer at the time), plug it in, and it works no problem. Let it cool down, plug it in again, and it won't start.
I changed the start-up cap and got all voltages working. Original cap was a Teapo SEK (a general purpose cap), 25v, 47uF. Replaced with Nichicon PM, 50v, 47uF. Cost me all of $0.08 .