Rca rlc3255a-b doa

[Fwrothy]

So I picked this up yesterday, no indicator lights.
No SBV
Fuse ok, no shorts and ~165vdc out from bridge.
Looking for SCH, no luck yet...

[tom66]

Re: Rca rlc3255a-b doa

Closer pic of PSU? Does 5V come back when you pull the power to main board connector out? Any ticking/pulsing sound from power board?

[Fwrothy]

Re: Rca rlc3255a-b doa

No ticks or hums or clicking don't see any relays anyway..
Tested SBV voltage with main board disconnected.
165v at main cap as well.

[Fwrothy]

Re: Rca rlc3255a-b doa

Better psu pic...

[budm]

Re: Rca rlc3255a-b doa

Is it MAGMEET MP118A? Pictures is not well focus.
Try heating those two caps with hair dryer to see if the 5VSTBY will start up or replace them.

[Fwrothy]

Re: Rca rlc3255a-b doa

Just found it @sj- it's a mp116a.

[Fwrothy]

Re: Rca rlc3255a-b doa

Is it MAGMEET MP118A? Pictures is not well focus.
Try heating those two caps with hair dryer to see if the 5VSTBY will start up or replace them.

Thanks Bud I'll give that a try!
Ya under the magnifying glass the 100uF looks bulged(bigger blue )-didn't notice before...

[Fwrothy]

Re: Rca rlc3255a-b doa

No luck with the hair dryer. Did pull out both capacitors(100mF 35v & 10mF 100v),no shorts,charged them with ohmmeter and drain back with voltmeter idk.
No luck with SCH either, so resorted to fishing.

Did notice short across octo didn't seem right; lifted it it seem ok. There's a sot 6 pin IC in area no idea what it is???
Found N MOSFET (F2HNK60Z) seems shorted , will pull next...
All these components are associated with primary of low voltage transformer.

[Fwrothy]

Re: Rca rlc3255a-b doa

MOSFET F2HNK60Z shorted D-S ....gate seemingly not shorted.

SOT6? PWM controller?

[Fwrothy]

Re: Rca rlc3255a-b doa

MOSFET F2HNK60Z shorted D-S ....gate seemingly not shorted.

SOT6? PWM controller?

Yes looks to me like a FAN6862...



Seems fried; Vdd,gate,FB all shorted to ground. That explain fault at octo.
Can bad caps cause this?!

[tom66]

Re: Rca rlc3255a-b doa

Blown FET can damage IC.
Replace IC, FET, and nearby resistors and diodes.

[Fwrothy]

Re: Rca rlc3255a-b doa

Thanks Tom, just repaired a similar situation but found some white residue on trace side of board oddly enough. Could that be leaked electrolyte?

[Fwrothy]

Re: Rca rlc3255a-b doa

So I got off my butt and found my camera, iPad doesn't seem to be cutting it.
Got a pic of the afore mentioned residue, looked like something I saw in 'worst soldering' thread (somebody had a go at it already I think), but what a difference, been squinting through the magnifying glass and camera lens for too long now I can see discrete component markings and ICs way better than naked eye! Would like to get an inexpensive USB microscope/camera...

Anyways, trying to get a parts list together and dunno how to spec PWM controller -mentioned a FAN6862 or similar a while back but there seems lots to choose from and I don't know anything about cross compatibility...

Any suggestions? Pic at least show package marking if that's any help.

[Fwrothy]

Re: Rca rlc3255a-b doa

Decided since I didn't have a SCH I'd try my hand at drawing one...at least the part that seems bad.
So here goes, most of it seems to make sense...any feedback would be appreciated on the plausibility of the circuits I've tried to interpret.
Btw q9 is the bad/ shorted MOSFET and there are various resistors hi-lighted that look damage as well as no reading/OL.

[tom66]

Re: Rca rlc3255a-b doa

R80/R81 will likely be low ohms. Are they through hole? Completely unreadable?
R73: typically 2~3x R74 value non-critical
R74: around 22 to 56 ohms check IC2 datasheet

[Fwrothy]

Re: Rca rlc3255a-b doa

R80/R81 will likely be low ohms. Are they through hole? Completely unreadable?
R73: typically 2~3x R74 value non-critical
R74: around 22 to 56 ohms check IC2 datasheet

I think the last pic shows them, r80/81 look like 4 digits.
They are all SMDs... Biggest issue is I don't know what IC2 IS...just guessing by pin layout .

[tom66]

Re: Rca rlc3255a-b doa

Looks like 2R20 i.e. 2.2 ohms which is about right.
Couldn't find any info on that IC either.

[Fwrothy]

Re: Rca rlc3255a-b doa

Ya it's a bugger... There are a few in the Fairchild roster that seem like they could work but idk how pick or compatibility issues. It's a $40 psu and available, plus the trace is lifting a bit (probably my fault when re&re ec7)-just trying to challenge myself.
Thanks for the input appreciated as always
Better pic..

[budm]

Re: Rca rlc3255a-b doa

If you do not get any where with it, replacement is not too bad.
http://www.shopjimmy.com/megmeet-mp1...upply-unit.htm