Sanyo DP42746 Y Board killed VS voltage

[Ltank]

I trouble shot LJ92-01200A Rev A A down to Q5009. It has 28 ohms the other have 2.4k ohms between E/B. There is no schematic for the board or is Q5009 listed in the parts. Does anyone know what the part is? The heat sink compound was hardened on it makes it unledgable. I can't really make out the others but little here and there. Don't all appear to be same # even though they physically look the same.

[tom66]

Re: Sanyo DP42746 Y Board killed VS voltage

Some IPA should dissolve the thermal gunk.
Then use some chalk and rub it over the markings... they should come out in the chalk.

[Ltank]

Re: Sanyo DP42746 Y Board killed VS voltage

Ok I got the Q5009 mosfet # TA36N30P from another member. Any other parts to replace with it? Shotkey diodes or resistors?
I Checked the LJ92-01200A buffer as described the Coppel links. my resistance checks showed 300 ohms in both directions on the upper board on almost all pins to the power pins. BAD? Guess I got to replace all the buffers. SN755870 QFPs? I had a lot higher resistance on lower buffer but i hope i checked them correctly. The Coppel link showed using the resistance not the diode setting on meter. Thanks Tom

[tom66]

Re: Sanyo DP42746 Y Board killed VS voltage

Personally I'd always use diode mode for the tests.
You should have continuity one way and nearly open (>100k) the other way.

[Ltank]

Re: Sanyo DP42746 Y Board killed VS voltage

One more thing. I have regular heat sink compound for Q5009. What thermal adhesive paste is needed to secure the heat sinks to the buffer ICs? Do I remove the heat sink before unsoldering the IC or remove IC/heat sink then remove heat sink from IC? Easiest way to remove it? What is best way to remove the silicone around the ICs?