Fixed a ViewSonic N3260w

[byacey]

Re: Fixed a ViewSonic N3260w

I checked the National 78L15 datasheet, and it appears it only needs a 2.5V differential to maintain regulation. Maximum current is 150ma, but I doubt the SM transistor is passing that kind of current.

[byacey]

Re: Fixed a ViewSonic N3260w

Double Post.

[Toasty]

Re: Fixed a ViewSonic N3260w

Not to dispute you as you have it in hand but that would be the oddest reflection...

[byacey]

Re: Fixed a ViewSonic N3260w

I looked again, definitely just a reflection.

[budm]

Re: Fixed a ViewSonic N3260w

7815AC sounds like the good one.

[byacey]

Re: Fixed a ViewSonic N3260w

Success. I tried a 78L15 regulator, but for some reason it loaded down the B+ standby supply too much and the power supply wouldn't switch on.

I installed a 2N4401 and a 15V zener, and everything is running perfect. I might look at installing a small fan on the chassis close to the AC power socket; this will blow air directly through the power supply heat sinks and hopefully help it to run cooler.

Thanks for all the advice.

[budm]

Re: Fixed a ViewSonic N3260w

Glad to hear it is working.

[Denbo]

Re: Fixed a ViewSonic N3260w

Same PSU (FSP212-3F01) is used on a Hannspree LCD TV (JT01-32U1-000G ). Had a look on this forum, replaced 7 Caps, Q7 and ZD4. LCD is now happy. Thanks BADCAPS!

[budm]

Re: Fixed a ViewSonic N3260w

Glad to hear another successful repair works.

[Craigsefton]

Re: Fixed a ViewSonic N3260w

Hi Everyone

I have a Viewsonic LCD picked it up not working, opened it up and assumed it was caused by the failed/failing cap's including one exploded (C33). So replaced the ones that looked bad. Was most and after reconstruction worked fine for a couple of months (not much use) but now after range of times screen fickers an dims and some times stops sound.

With some work on amps previously when I couldn't get the right size/V cap from
local supplier I would get the next size/V up. Could this be the cause?
Or should I get a tool to test the cap's?

Thanks for any Help

[12rounds]

Re: Fixed a ViewSonic N3260w

hello gentlemen,
came across this thread while trying to finish repairing a fsp212-3f01 psu in a viewsonic n3251w. I started with a dead totally dead tv - even after replacing all the visibly exploded electo caps. replacing q7 and the adjacent zener brought the +5vdc portion back to life, giving me a red led on the front which will turn green when pushing the power button. My problem is that now i don't have the +12 and +24. Any thoughts as to where to start?
Thanks!

[budm]

Re: Fixed a ViewSonic N3260w

Check and see if the power supply board is getting the PS_ON signal or not, also check the DC Voltage right at the two legs of the main filter cap in the primary side, if the PS_ON is good, then you should have >360VDC on the filter cap.

[12rounds]

Re: Fixed a ViewSonic N3260w

getting a psu on signal at p10 of cns1; going from ~60mv - 3.4vdc, which i believe is too low (5vdc normal high?). only 153vdc on primary side of big cap whether led is green or red. psu isn't turning fully on, correct?

[budm]

Re: Fixed a ViewSonic N3260w

PS_ON >2.5VDC = ON, <1V = OFF. So you are getting 3.4VDC and the Voltage on the cap did not go up from 170VDC to >360VDC.
Can I see good clear pictures of YOUR board, both sides of the board?

[12rounds]

Re: Fixed a ViewSonic N3260w

i gave it a quick visual and didn't see anything looking like component damage... thanks for putting fresh eyes on it!

note: i haven't replaced the 5 small electro caps yet - waiting for parts from digikey...

[budm]

Re: Fixed a ViewSonic N3260w

OK, we weed to find out if the PFC IC is getting the Voltage for the VCC pin or not. Please get the numbers on that PFC IC, see if it matches the SCH.

[12rounds]

Re: Fixed a ViewSonic N3260w

i have its datasheet - i will check tomorrow after work. its a 28051; i believe its a TI component, ucc28051.

[budm]

Re: Fixed a ViewSonic N3260w

See the SCH I just uploaded.

[12rounds]

Re: Fixed a ViewSonic N3260w

found that a bit earlier today... didn't have time to start going through and verify it is accurate - weird drawing name and part designators, but it looks pretty close. is it completely accurate?

[12rounds]

Re: Fixed a ViewSonic N3260w

so the PFC ic is not getting voltage on vcc. it is reading like this:
p1 vo_sns = 0.97v
p2 comp = 0.5v
p3 multin= 1.22v
p4 cs = 0
p5 zdc = 80mv
p6 gnd = 0.2mv
p7 drv = 220mv
p8 vcc = 200-230mv

looking at the schematic that you had attached, i don't see any of the discretes required to operate this ic. going to look at the reference design and see how close the 2 are.

other thought - i should be getting much more voltage through the rectifier bridge than i am. metering out the bridge (diode check, in circuit) shows it looking ok, except when reading though 2 diodes (negative out to positive out). i would expect to read the drop on both diodes in series ~ 0.7, but i am getting ~0.4 from line/neutral in to + out and - out to + out.