Need Help With Lite-on With No Power After Probe Spark Problem, lite-on dg-16D2S 74850c mpx01 pad, probe touched capacitor lead closes Options

[h4x0rm1k3]

Hi all,

I had someone bring a phat 360 over with a lite-on drive the other day and while probing the probe touched something it shouldn't have (the capacitor lead closest the probe pad mpx01) and now the drive refuses to open or close or even allow me to read the key off of it! I was probing mpx01 and somehow managed to allow it to touch the lead of a capacitor (the 10v 220uf one closest to the mpx01 probe pad!) which caused a small spark.
Since then I can't do anything! Is there anything that I should be looking for with a multi meter which I have access to? I also have access to another lite-on which i've had lying around for ages which I can use as spares which the laser had died on so the board should be ok!
What I need to know is what parts to check 1st with the multi meter and then also wether during the arc over if the chip with the key may have lost it's memory because of the voltage going through the mpx01 pad? Also, the resistances i'm looking for to tell which part may be fried or not would be handy.
Any help with this would be appreciated as the person I'm doing it for doesn't know yet quite how serious it might be as i've only told him that while probing a resistor must have blown which I have to trace down ( he's of Indian origin and speaks little english!) I'd rather fix it as quick as possible as by sounds of it he could put a lot of work my way which I wouldn't like to lose over a silly mistake I made (never happened to me before in over 100 probe sessions!)
Thanks in advance

[wilgo45]

Could be the Cap you mentioned is now knocked out due to the short or exposure to voltage.

Would be easy to take out and test. Just unsolder it. Some DMM's have capacitance test functions.

Could also be - you shorted out a primary transistor for power regulation there on that pcb. Once that's swapped it could all be better.

I helped Tdezel recently with a troubled Lite ON pcb. Patched his damaged traces and extracted his drive key and other info.

He sent things to me from North Carolina

From now on cover the surrounding area with tape. Just leave the probe area exposed. It just safe guards the job and only takes a few minutes.

[h4x0rm1k3]

Thanks for the reply. I will definitely be taping the surrounding areas in the future as you say, it only takes a few seconds to do so! Anyway, any ideas on what setting I should use on my multi meter? (I know, sounding like a noob) I only really use it for pot tweaking and a couple of other things so from guides I already gained the info for the settings I needed. The meter I have is a fairly basic one that cost about £15 on ebay. It has the usual settings, like this if you can understand what I mean! ( V- with 3 dots underneath goes from 200m to just 600 near the off position, V wavy line 600&200, A- with 3 dots underneath again 200u to 200m, Lastly the ohms area has 200 to 2M. It also has the continuity, hfe & 10A positions)
I will try and transplant the working cap out as replacement and see how that goes. Apart from that I just need to know where to check/test and what settings to use to work out what may need replacing. I know that i'd be able to do it with the right knowledge but without that info i'm a bit lost!
Again, thanks for your reply and I hope to hear from you again with possibly a bit more info if you're able to provide it.

[wilgo45]

Thanks for the reply. I will definitely be taping the surrounding areas in the future as you say, it only takes a few seconds to do so! Anyway, any ideas on what setting I should use on my multi meter? (I know, sounding like a noob) I only really use it for pot tweaking and a couple of other things so from guides I already gained the info for the settings I needed. The meter I have is a fairly basic one that cost about £15 on ebay. It has the usual settings, like this if you can understand what I mean! ( V- with 3 dots underneath goes from 200m to just 600 near the off position, V wavy line 600&200, A- with 3 dots underneath again 200u to 200m, Lastly the ohms area has 200 to 2M. It also has the continuity, hfe & 10A positions)
I will try and transplant the working cap out as replacement and see how that goes. Apart from that I just need to know where to check/test and what settings to use to work out what may need replacing. I know that i'd be able to do it with the right knowledge but without that info i'm a bit lost!
Again, thanks for your reply and I hope to hear from you again with possibly a bit more info if you're able to provide it.

On the meter .... V- with dots volts DC. Wavy line - volts AC

On your particular problem: you want to use either Continuity or a low Resistance setting. Continuity is what I usually use. If yours has a beep feature with that - great.

You'll want to use the power pins on the PCB. Top row of pins should be Grounds - most of them. Put a negative probe there. Keep it there. Or find a ground area on the PCB.

Basically three power rails to the dvd drive. 3.3 , 5 and two 12 volt lines. Each at a turn. Place your positive probe on those pins. Start on one, move to the next.

If your meter gives a continual beep or shows perfect continuity from one volt source to ground - then you have a short in that voltage rail. Then you try to narrow it down to a component

Kind of hard writing how to do it. So much easier to show someone directly

Would almost guess you have a short in the 3.3 volt rail