Identify Schottky diode on Realtek 1073 based mediaplayer

[re-atari]

Hello all,

I have been a long time reader and occasional poster on this forum, more specifically in the computer display repair subforum. I have repaired lots of them either by recapping/replacing fets.

Now I'm having a bit of trouble with a Woxter i-cube 750 mediaplayer, and could use a little input to get it on its feet again. I got it in non-working condition, the owner could not tell me more than 'it gradually detected the built-in harddisk worse and worse, and now it doesn't detect it at all anymore. The player itself does start up'. It looked to be just a defective harddisk, easy to replace. Lo and behold (of course), when I received the unit it was exactly the opposite: the harddisk (DiamondMax 9 120Gb) was in perfect order, but the player would not startup.

Opening the case it turns out this mediaplayer is basically an implementation of the Realtek RTD-1073 reference design. This is the case with a lot of them out there, such as AC Ryan Playon HD, Mede8er 500X, my Woxter, they are all built around the same mainboard.

Doing some checks with my multimeter, I found out there's a problem with the power circuitry. It should provide 12V, 5V, 3.3V, 1.8V and 1.2V. All but one were present, the 1.2V line was way too low at only 0.5V.
This voltage is generated in a circuit built around a AP1539. Similar to the datasheet it has a smd Schottky diode and 470 uF buffer capacitor on its output Voltage line. I suspect that one of them, or maybe even both, is shot. They are connected in parallel between V-out and GND. With my multimeter on diodetest the diode measures zero Ohm in both directions, so I do not even get a reading of the cap charging. My intuition tells me the capacitor is the culprit, although it does not show any damage or burst vent on top. It may well have taken out the diode in its demise. I haven't replaced the cap yet, but will do so for good measure. I intend to desolder it anyway in order to check the condition of the Schottky diode.

Now I can't determine which Schottky diode is used, and could use some help in identifying it to find a potential replacement in case it turns out to be shot after all. Looking at the marking on top the logo appears to be by Diodes Incorporated. The complete marking is:

|)|| 919

SV4
__ 26

Great things these smd's, very informative...

Does anyone have any idea what kind of Schotkky diode this could possibly be, and which ones are a suitable equivalent? The AP1539´s datasheet suggests a B540 or PDS540 from Diodes Incorporated, but according to their datasheets these have different component markings on top. Are there general rules how to go about when selecting a suitable equivalent?

All info much appreciated!

Regards,

re-atari

[jetadm123]

Re: Identify Schottky diode on Realtek 1073 based mediaplayer

Possibly a Diodes, Inc SD103AW?

[ben7]

Re: Identify Schottky diode on Realtek 1073 based mediaplayer

If this schottky went bad, I would go with a higher reverse voltage rated one.

I think it is actually an SBR3U40P1 by diodes inc.
The datasheet shows that the marking is 'SV4'.

Could you possibly get a picture of this diode, so we can confirm it?

[re-atari]

Re: Identify Schottky diode on Realtek 1073 based mediaplayer

Hi guys,

Thanks for your replies, much appreciated!

I did some googling around after posting my story, and stumbled across both as well. The marking on the SBR3U40P1 seems to match a bit more closely than the SD103AW, but is not identical. For now it's a moot point, however, as the Schottky diode seems to be allright after all. I already tried to take a picture, but they all turned out a bit blurry. The marking is just like I described in my opening post.

Yesterday evening I desoldered the suspect cap, but my oh my, what a job that turned out to be. Usually a bit of fresh solder (i.e. resin) and some heat helps a lot in any desoldering job, but not this time. At first the solder just would not stick, I think because the PCB was manufactured using leadfree solder. Besides that, the voltage and GND layers inside the PCB drained a lot of heat from my soldering iron (24W). So much in fact that I could not get the cap to wiggle, but (of course) it did heat up enough to burn my fingers. I have recapped several PC mainboards, so I know how to deal with multilayer PCB's, but this was just insane. At last, after no less than 15 minutes and with several aching fingers, I finally managed to remove it. Without damaging traces or the through-holes

Sadly, all looks to have been in vain. With my multimeter I still got continuity across the Schottky diode, so I desoldered it on one side. Turns out it is OK after all, as on diode test I now measured infinity in one direction and a steady 91mV (or so) the other way around. But there still was continuity between the 1.2V voltage rail and GND (measured on the solder pads of the desoldered cap). So I decided to just resolder the diode and put in a brandnew 470 uF low ESR cap to be on the safe side.

Now I haven't started up the PCB yet, first I want to wipe off all the resin with acetone and check my soldering with a magnifying glass. That, and some thorough measuring, is on my list for tonight. I don't have high hopes the player is now suddenly magically revived

If the 1.2V voltage turns out to be still too low, that would only leave the AP1539, numerous 100nF ceramic caps on the 1.2V voltage rail, or the Realtek 1073 as defective. Goodie...

I'll keep you informed!

re-atari

[re-atari]

Re: Identify Schottky diode on Realtek 1073 based mediaplayer

Last weekend I finally managed to spend some 'quality time' again with this mediaplayer. Replaced just about every cap in the PSU circuitry, but sadly that did not fix it yet. No change in behavior. The mediaplayer just does not start up, and does not switch off either. After pressing the on/off switch both the blue and red led behind it are lit. The big Realtek IC does not warm up at all.

After my earlier repair attempt (replacing just one suspect cap) I did some measurements with my multimeter. Turned out the AP1539 is not supplied any Voltage input (it's literally 0V). So, no wonder that it doesn't output the Voltage that it's supposed to. My gut instinct told me one of the other caps was causing this, and decided to replace them, even if it's just for good measure. Should have known better, though, since the other Voltages were OK

That leaves tracing the circuitry to identify the component(s) that should supply this Voltage. To complicate things a bit further, the PSU circuitry (of course) differs quite a lot from Realtek's reference design in the official docs. Or in plain English: draw out the circuitry by yourself. Easier said than done on this multilayer PCB. Sigh...

re-atari