unknown IC on Westinghouse LCD power supply board

On Sat, 07 Mar 2009 20:24:17 -0500, Rick put finger to keyboard and composed:

The logo belongs to Alpha & Omega Semiconductor, Inc.

The part number is AOP605. It is an N-Channel Complementary Enhancement Mode Field Effect Transistor, 30V, 7.5A.

BD6L2P and BD6L2B are actually date/batch codes.

Here is the datasheet:

- Franc Zabkar

On Sun, 08 Mar 2009 13:42:54 +1100, Franc Zabkar put finger to keyboard and composed:

Sorry, it's a dual N-channel and P-channel MOSFET.

Available from Digikey for $0.87:

- Franc Zabkar

Thanks Frank! I was at Digikey - how did I miss that?

It looks like a fairly robust part and I'd expect to see a certain amount of thermal discoloration around those IC's on the circuit board. The owner swears the damage occurred during a single power on attempt - says she got nothing at all when she turned the monitor on after it had been powered off for about a week. No smoke, didn't hear anything.

Unlikely the MOFSET's are damaged since the capacitors - and the fuse - on the power supply board blew? Any thoughts? (Damned cheap electrolytic capacitors...)

Rick

On Sun, 08 Mar 2009 07:39:59 -0500, Rick put finger to keyboard and composed:

Since the fuse blew, and assuming it wasn't just "tired", I'd be looking for shorted components. That's how MOSFETs usually fail, IME.

Having said that, I've seen many posts where replacing capacitors and picofuses was all that was required.

- Franc Zabkar

not

You know the caps need replaced, they were lossy and possibly one shorted, pull them all off and check for shorts. Also check the transistors for shorts, if the caps were bad enough it could have blown one but no need to assume one way or the other, if they are you will find it with a multimeter. If it's a matter of ordering all the parts in a timely fashion you could go ahead and order those too, then wait to see if you need to replace any. Since they were getting quite hot, inspect the traces to them in case those started to delaminate from the board.

This is a common problem with these monitors. Cheap capacitors, poor ventilation, and suddenly you have a failure. The ususal chain of events is the caps degrade, resulting in high ripple. Then things deteriorate from there. I've had many that require only cap replacement. In one case, the only other problem was a blown fuse in the inverter. Common symptoms include turning on, then off again; backlight turns off, then on, backlight won't turn on, fuse blown, etc.

There is a lot of information on the problem at

Recommendation is to replace ALL electrolytic caps in the power supply and inverter with Panasonic FC, Nichicon PM or equivalent. You already mentioned Digi-Key. I was thrilled recently to discover they no longer have a handling charge for small orders. The caps to redo two monitors cost less than $10 - delivered.

PlainBill