ID this transistor in KOSS 22" LCD TV/Monitor?

[Wizard]

Here's this Koss made by generic maker of this 22" LCD TV/monitor with dead lamp inverter board. I was able to detemine this transistor of the pair is kaput.

Issue is need to identify this one, can't find good answer with google and couldn't ID this logo, as far as I can detemine it does have NPN or N mosfet and this seems to have a diode or zener across C to E or D to S. Set up as dual transistors totem pole drive that drives all 3 transformers for 6 lamp tubes.

Reason I need to ID these and what it is typically used. So I can substitute them with ones from my junkbox.

Doesn't have external damper diode or coils at all, just direct drive.

As far as I can determine this came about with evil tan glue that did conduct and fried the one of the pair transistor, cleaned glue (crumbly) up.

Here's the pic:



Cheers, Wizard

[kc8adu]

Re: ID this transistor in KOSS 22" LCD TV/Monitor?

here is the mfr.
http://www.aosmd.com/web/index.jsp

[Krankshaft]

Re: ID this transistor in KOSS 22" LCD TV/Monitor?

Thanks for the site KC.

I did some hunting on that site here is your datasheet.

I couldn't direct link it so I uploaded it for you. It's an N channel MOSFET.

[Wizard]

Re: ID this transistor in KOSS 22" LCD TV/Monitor?

Awesome! Now I know what this is and that confirms my suspicion that measurements matches what I see for a MOSFET with a diode. Was not sure which zener or a diode.

What kind of the diode it is used, high speed or ultrafast or deflection horizontal damper diode type of specifications? If I have the info, I can cobble together a working soluton with the spare parts at my shop.

Cheers, Wizard

[Wizard]

Re: ID this transistor in KOSS 22" LCD TV/Monitor?

Success! Like I said, caps were not the problem, it was degraded glue that distorted the waveforms for driving the pair of MOSFETs and blew one. Replaced both with FDD6690A MOSFETs off a scrapped notebook.

But I have a issue, these pair is 30V rated, while the old ones were 60V. The LCD power is 19V and is fed to the mainboard and this is also goes to the LCD lamp inverter supply.

So far I have not found the 60V rated N channel MOSFET with damper diode across D-S.

Ran 5 hours so far with no issues.

Cheers, Wizard

[envisionelec]

Re: ID this transistor in KOSS 22" LCD TV/Monitor?

Success! Like I said, caps were not the problem, it was degraded glue that distorted the waveforms for driving the pair of MOSFETs and blew one. Replaced both with FDD6690A MOSFETs off a scrapped notebook.

But I have a issue, these pair is 30V rated, while the old ones were 60V. The LCD power is 19V and is fed to the mainboard and this is also goes to the LCD lamp inverter supply.

So far I have not found the 60V rated N channel MOSFET with damper diode across D-S.

Ran 5 hours so far with no issues.

Cheers, Wizard

The reason that 60V devices are used is that the D-S voltage in a push-pull or forward converter is twice the input voltage. Your replacements will eventually fail, too.

Replacement parts like an IRLR-series in DPAK work perfectly, rated at 60V and have a body diode. I use these in all my smaller (<20W) power supplies.

http://www.digikey.com/scripts/DkSea...ame=IRLR014-ND


Regards,
A. Hammett

[Wizard]

Re: ID this transistor in KOSS 22" LCD TV/Monitor?

I know that, and that is EXACTLY what I wanted to hear, care to sell two transistors? Or suggest alterative sources in the devices where I could go digging to sub these two?
All the notebooks and other smaller LCD inverters uses 24-30V rating.

Oh, have happy new year!

Cheers, Wizard