Protron PLTV3250 Power Supply Issue

[cguzek]

Before i start i will let everyone know that i have read other posts about this power supply.

I started with a dead power supply. Board is FSP194-3F01
No standby 5v.
Read forums here, replaced bulging caps, also replaced transistor Q7 and surface mount 15v zener diode zd4 (i am not going to lie, i used a pin through 15v zener diode 1n4744a, cut leads and bent to make fit surface mount area, not sure if this could be part of problem. I have ordered surface mount zener diodes, currently awaiting them.), like previous thread recommended.

Voila, i have 5v standby. I am now pretty excited. I put everything in place, plug in, and flip power switch. I have red led in front now, never had before. I click the power button on the front bottom panel, and the blue light near the menu button lights quick, and red led turns green. No picture. I took a flashlight, and shined it through screen. I can see picture snow when light shined in, and screen seems completely intact.

I am now thinking that it is the backlight inverter as I recently replaced a fuse on one to get it to send out voltage. I test backlight inverter output and have nothing. Hoping it is the fuses, i test fuses, and they are good (all surface mount). It is not they all are good. Next i test input power coming from power supply. It is only getting 16.8 volts from the power supply when it is supposed to be getting 24v.

When testing the power supply, i now notice that after hitting the power button, not only do the cns3 and cns4 only output 16.8v instead of 24v, but also cns2 only puts out 10.8v instead of 16v.

I hope somebody can help me with this problem. Between looking up information in forums, and waiting for parts to arrive, i have been working on this power supply board for over a month now. I know i am close to finally getting this tv to work, and any help would be appreciated.

By the way, i have not done any testing of any of the other boards inside as i am pretty sure it is still just a power supply issue, but other boards "look" okay, even though psu did not(no burnt/bulged caps, etc.)

Thank you.

[Wizard]

Check the resistor either 4.7 or 5.1 Ohms from standby transformer that goes to diode that goes thru another resistor then zener as you mentioned.

Use the multimeter. Remember power cord unplugged!

Cheers, Wizard

[cguzek]

ok, have board in front of me, i am assuming also that you are talking about hole through component side, as there are no diodes near that area on surface mount side. I am also assuming that the standby transformer is the smaller transformer nearest to the standby output.

On the primary side of board there is one larger resistor, color violet7,green5, orange000, gold+/_%, so that is 75000value?, it is inbetween a ceramic capacitor and a diode with an added metal cylinder (like a smaller version of the thing that sometimes a power cord is wrapped around), next to that is another resistor with brown1, black0, black0, gold = 10value?, after that, i do not see a zener, just more resistors. If it is 4.7 or 5.1 it would start with a green or yellow band.

After writing all of this i looked at the surface mount side again and noticed some surface mount resistors, 1 which says 5R1 which is 5.1 ohms, is this the one you were speaking of down and right of the bad zener diode. Well, i'll try and get some pics up of both areas.

[cguzek]

Here are some pics, not sure which side of board resistor is you are speaking of although i am leaning towards surface mount.

[Wizard]

Yes. that resistor is it good?

And, make sure that small capacitor (electrolytic) is replaced. Also one or two small capacitors in PFC circuit and other small caps (in hot side) for 24V supply as well.

Cheers, Wizard

[cguzek]

ok, i took off the resistor that is in question r65, 5.1 ohm smd resistor. I tested it on the 200 ohm test, and it reads 6-6.1 ohms, does this mean that it is bad, too much resistance?

As for the capacitor that is out, i decided it would be a good idea to replace all caps on board. At first i only changed out bulging ones. Waiting on them and 5r1 resistor in mail.

[Coronelac]

I have the same exact problem. Although, I tested the supply unmounted and I'm only getting a 5v current. I have no 16v or 24v. All caps on non-surface mount side replaced except for the biggest one, my 5R1 resistor reads 5.4 ohms and the drops to 5.1, also replaced the zener diode and Q7 transistor; any ideas?

[budm]

The 16 and the 24vdc power supplies get the turn on sihnal from the logic board, look at the power supply board, you will see O/F pin on CNS1, there should be about 3.3vdc on this pin to turn on the 16 and 24vdc supply. 5.4/5.1 Ohms resistor is fine (within 5%).
http://s807.photobucket.com/albums/y...20PLTV%203250/

I replaced the bad caps wIth PANASONIC FM, FC series from DIGIKEY, and also the shorted out Q7 (2N2222) and ZD4 (15V ZENER) in the 5vdc standby power supply section.

[Lccomputers100]

So what happened I got the same trouble I have done all of the above and still nothing I got 5 volts stb but then it ust stoped i never got 24 v or 16 v how di you guys fix it to get 24v and 16v i am not worried about the 5v i can fix that but i am stuck with the 24 and 16v help me out please

[alfa88]

My 1st. post to this group. I wish to extend my thanks to the brainiacs that helped me breathe life back into my Protron.
I would like to add a few tips.
To do a Zener test look up a tutorial on Google. A simple diode test is close to useless. Tack on a couple of wire wrap wires and do an in circuit test (board removed, power off, using above test.)
Change all obviously bad components.
Remove and perform an active MOSFET test (look it up on Google, it's not a difficult test).
The rest of the parts can be checked statically.
Get an eye loupe, tweezers, needle nosed pliers, Xacto knife, solder sucker, solder wick and a fine tip soldering iron.
Relax and take your sweet time.
Forget about reinstalling surface mount components; they are a necessary evil of the 21st. century but through hole will work nicely in this instance.

[pauldow]

I know there are more recent threads on this topic, but it looks like the symptoms described in this topic are the closest to mine.
My problem is that I do have 5V standby, and I get 3.3V when I press the power button. The power LED changes to blue when pressed. No picture or sound on the set. I don't get 16V or 24V.
I did have some bulging capacitors, so I replaced all the electrolytics. I think I need to invest in an ESR meter if I'm going to do this type of stuff, so I'm not sure of the quality. I used mostly NTE capacitors. I do get 163 V across the big capacitor.
I replaced Q7 and ZD4. (I didn't get the 5V before that.) R65, the one labeled 5R1 reads 5.2 Ohms.
I have some toasty looking PC board area around Q4 (FQPF5N60C) so I changed that along with ZD3.
Since I was ordering parts, I added a few K3568 FET, and changed those. No difference, but they were only a couple dollars.

Well, I've run out of reading other solutions, and was wondering if there's another thing to check, or if I need to consider buying a new supply. This one seems to run about $60, so that may not be prudent for a seven year old TV.

Thanks,
Paul

Good thing I did a Ctrl-A Ctrl-C before I hit the post button. The people on this board are great, but why is the login time out only about 5 minutes?

[cheapie]

Originally Posted by pauldow

Good thing I did a Ctrl-A Ctrl-C before I hit the post button. The people on this board are great, but why is the login time out only about 5 minutes?

???
It isn't for me... *checks cookie expiration dates* It looks like it's one year...

[pauldow]

Hmmm.

I have Firefox set to delete cookies when I close the session. It shows all my badcaps.net cookies expire at the end of the session.

Oh well. It's not too much trouble. I've got other much more important things to frustrate me.

Thanks,
Paul