Re: Pioneer Plasma Model# PDP-5070PU main board bad?

if its the input ( voltage on the bulk input caps ), follow EVERYTHING back from the mains input.

Movs, fuses, shorted bridge diodes, bulk caps

after all that check boost transformer, boost trannys, replace boost controller as a mattar of course.

It could be though the DC voltage on the boost caps is too high for your meter and will go 0L

Re: Phillips Brilliance 230c 2 secs to black

CCFL resistance all reading 0L (Probably above the 10M range of my meter).

One CCFL Reads 1.6M, assuming its bust.

Windings seem to have decent inductance. Also going to take out the cap on the soft-start pin tonight........ see if that makes any difference.

Wiring looks OK but going to replace tonight hopefully. Anywhere I can get new ones for this model???

Hi all,

I'm a graduate power supply design engineer so diagnosing the power supply in this beastie isn't a problem.

This is the inverter, which I believe is fine: [url]http://www.super-laptop-parts.com/ilpi136-power-supply-board-philips-230e-lm230wf1-p-12866.html[/url]

I've replaced all the caps but the main bulk cap as these are unlikely to blow.

I'm getting a stable 5v on the output rail, and 24vac (strange) on the output of all 4 inverters. I looked at the switching waveforms on the scope and they're all square waves 50% duty and the...

Re: help with mosfets and switching regulator!

if you can get a high-res picture of the top and bottom of the board it would help.

also a good idea would be to draw out a schematic of the whole power supply. or at least the outputs that do not work,

Re: help with mosfets and switching regulator!

ps, as far as testing chips go, you COULD look at the switching waveform (The GATE of the fet) on an oscillosope

Connect a digital load (or multiple low ohm power resistors) and increase the current draw from low to high. The switching waveform _should_ be a low % duty cycle at light loading, and up to 95% for almost max load.

Likely story is you won't have this equipment. I doubt it's the chip, but they cost like $2 so you aren't loosing anything if you replace the chip...

Post a schematic and...

Re: help with mosfets and switching regulator!

look at the datasheet for the fet. assume a new fet is perfectly working and doesn't need testing. you should always replace fets like-for-like. If you cannot find one that is exact, look at the datasheets and compare all of the specs. It's like putting an exhaust from my mate's Corsa onto my Civic...

the DRAIN to SOURCE resistance should be 0L
but the SOURCE to DRAIN resistance usually will be pretty low (fets have a diode from src to drain)

this is assuming n-channel enhancement fets. That should help...

Re: New Members - please post your introductions here

hi all, chris here . graduate electronics engineer working on high-reliability power supplies for the past ~9 months.