emerson BA01P0F0103 3 transformer squeals

[martino]

Hello all,
TV is a phillips 42pfl3505
Power supply is a BA01P0F0103 3

Problem: As soon as you plug in TV,a loud squeal/buzzing from transformer T601(see pic#2,I'm pointing my finger at it),the squeal starts kinda high in frequency and slowly frequency goes lower,as if it is grunting down to a halt.

I proceeded and de-soldered T601 and measured the pins according to diagram in pic#4.

Measuring the points on the board where T601 sits,non of the pins measures a short.

Measuring the T601 I get the following values:
pin 1-3=0.3ohm
pin 5-6=0.3ohm
pin 6-7=0.3ohm
pin 5-7=0.4ohm

At first glance,does that sound shorted to you?
If so,where could a person buy one of these? (pic#3 has the numbers on it)

p.s: I searched forum and could only find threads where fuse blew,with shorted diodes,mine fuse stays intact...

[ben7]

Re: emerson BA01P0F0103 3 transformer squeals

Hello all,
TV is a phillips 42pfl3505
Power supply is a BA01P0F0103 3

Problem: As soon as you plug in TV,a loud squeal/buzzing from transformer T601(see pic#2,I'm pointing my finger at it),the squeal starts kinda high in frequency and slowly frequency goes lower,as if it is grunting down to a halt.

I proceeded and de-soldered T601 and measured the pins according to diagram in pic#4.

Measuring the points on the board where T601 sits,non of the pins measures a short.

Measuring the T601 I get the following values:
pin 1-3=0.3ohm
pin 5-6=0.3ohm
pin 6-7=0.3ohm
pin 5-7=0.4ohm

At first glance,does that sound shorted to you?
If so,where could a person buy one of these? (pic#3 has the numbers on it)

p.s: I searched forum and could only find threads where fuse blew,with shorted diodes,mine fuse stays intact...

Nope those resistances are normal, they are actually probably much lower than that, but most meters don't measure resistance much lower than that.

It is quite rare for a smps transformer to fail. It is more likely for the backlight transformers to fail, since they operate at a higher voltage.

That ticking/squealing sound is typical of an unstable SMPS (not regulating properly), which can be caused by a number of things. Bad capacitors, bad resistors, bad IC's and transistors, or bad opto-couplers just to name a few.

Are there any parts on the bottom of the board around that area with the noisy transformer? If so, could you get us a pic or two of that?

[R_J]

Re: emerson BA01P0F0103 3 transformer squeals

I would check for a shorted diode etc. in the secondary, sounds like something is loading down the power supply.

[martino]

Re: emerson BA01P0F0103 3 transformer squeals

Took a couple of pics from the bottom side of board around the squealing coil..
I also found this pdf that shows top and bottom in see through..I attached it,hope it shows up(don't know how to attach a pdf)

I could use a bit of guide on where to start trouble shooting,been poking around a bit with my dmm but didn't find a obvious short.
One guy told me once,that a squealing coil often means a badly driven coil,making me snooping around in the driver portion of the coil,any truth to that???
I ordered a ESR meter,should be in any day now

Hope these pics/pdf help.
Am I correct in saying that pic3 shows the ACdetect circuit?

[martino]

Re: emerson BA01P0F0103 3 transformer squeals

Gentleman we have a fix !!!!!

On suggestion by R_J I poked around in the cold side and sure enough,I found a shorted diode!
The diode is a FR104,I only had a FR103,looking at the spec's I believe them to be "close enough",am I correct or should i order a FR104???

For anyone reading this post,having the same problem,it was diode 651,located very near transformer T601.It's in the 35volt rail.

Thank you gentleman in your as always awesome assist

[ben7]

Re: emerson BA01P0F0103 3 transformer squeals

Gentleman we have a fix !!!!!

On suggestion by R_J I poked around in the cold side and sure enough,I found a shorted diode!
The diode is a FR104,I only had a FR103,looking at the spec's I believe them to be "close enough",am I correct or should i order a FR104???

For anyone reading this post,having the same problem,it was diode 651,located very near transformer T601.It's in the 35volt rail.

Thank you gentleman in your as always awesome assist

Good job, however,
Noooo!, use an FR104 or greater (FR105, FR106, FR107...)
The FR103 is rated at a maximum reverse voltage of 200V, whereas the FR104 is rated at 400V. This could cause an early failure of the FR103 diode you put in there.

[Pentium4]

Re: emerson BA01P0F0103 3 transformer squeals

Nice job! I would also recommend replacing all the caps, as they are only rated for 85C

[kca]

Re: emerson BA01P0F0103 3 transformer squeals

Hello martino ~

Did replacing diode 651 fix your problem?

Or, did it take that and something else in combination with that?

I have the same transformer hissing problem on my Philips 46PFL370D/F7.

~ kca

[martino]

Re: emerson BA01P0F0103 3 transformer squeals

Nope, just that diode. Gave tv to brother in law and it still works fine today

[kca]

Re: emerson BA01P0F0103 3 transformer squeals

That's good to know! Thank you for the reply.

Do you think any of these readings are out of line such that the diode(s) need be replaced?

I don't have a great deal of experience yet w/ diode readings/replacement, so any advice you can give would be most appreciated.

PHILIPS 46PFL3705D/F7

D651 = 565
D652 = 566

D656 = 253

D662 = 155

D665 = 525
D670 = 175

D672 = 193
D673 = 193
D674 = 193

The above readings were taken in Diode mode on a Craftsman DMM, and when I reverse the leads I get a reading of 1 on the left-hand side of the screen. There are no OL readings. Is this the best way to gather the readings?


Attached is a pic of the diodes currently in question near the transformer that is making the problematic squealing/hissing sound.

[kca]

Re: emerson BA01P0F0103 3 transformer squeals

Also, I am wondering if you know if other boards in the set, if defective, can cause this type of squealing in the PSU transformer?

I ask because when I disconnect all of the cables leading out from the PSU, the tv no longer shuts down and there is no squealing. I only get a "silent" black screen. When I reconnected all of the cables and ribbons one by one, the squealing returns. I haven't done exhaustive testing of this as of yet, but one result is that everything could be plugged in EXCEPT the tuner board and it was still black screen silent. Then, when I made that last connection of tuner board to PSU via the small white ribbon, that's when the transformer would start its familiar squealing/humming again.

The same result, however, occurred when I left the tuner board connected up to the PSU and isolated the board above it (where the HDMI ports are). All black screen silent until I made that connection between this "HDMI port" board (sorry, can't think of its proper name at the moment), and the tuner board via two white ribbons. I think there are other combinations that would likely produce the same result.

So, my question is .... could it be that one or more than one of these other boards in the set is producing the squeal in the transformer, or is it the case that the squeal must be stopped at the PSU level itself and then the other boards are likely to function in their normal manner? It seems like both notions have merit.

[Shane711]

Re: emerson BA01P0F0103 3 transformer squeals

I have noticed that D652 also causes the transformer to squeal. Also check D614. I have one that will not turn on, I am starting to suspect a bad resistor because I have no shorts on the board. I have been fixing about 3 of these power boards every week because I offer a repair service for it. But I have not experienced every possible problem yet. Soon I will be an expert on this board but it is stressful.

[kca]

Re: emerson BA01P0F0103 3 transformer squeals

Thank you, Shane711 ~

I have put this particular set on the back burner because I could not get it to fire up back in the spring.

I will take a look at those two particular diodes you just pointed out. I agree that this set and its respective boards seems to be a little touchy and its hard to diagnose the exact source of the problem.

Because you've fixed a few of these in the past already, I am curious as to your opinion of the picture quality that results after the fix. How would you rate it?


~ kca

[Shane711]

Re: emerson BA01P0F0103 3 transformer squeals

LOL, The TV I am using to fix all these boards has a broken screen so there is no way I can tell what the picture quality is. I figured since the screen was smashed I might as well use it for a test TV. I fixed 14 of these board in the past month. I have one now that will not turn on. I found D614 to be shorted but still won't turn on. I think I have narrowed it down to IC1401. I will change this IC tomorrow and see what happens. I also have another board that keeps blowing the fuse and 2 diodes but I have not been able to figure out why, I am suspecting 1 of the high voltage capacitors because I can't test them. D652 will definitely cause the transformer to buzz so be sure to check that.

[Shane711]

Re: emerson BA01P0F0103 3 transformer squeals

Sometimes when you have the board squealing and then after you replace the diode, if it blows again it usually means you have a bad audio/input board. If you do not fix the audio board the power board will blow every time. Working on 4 of these boards today and I have another one that will not work after replacing all the parts, but this board was damaged, has cracks and broken pieces.