BA3AU0F0102_3 PSU transformer chirps every 2 seconds

[fubr]

I have a BA3AU0F0102_3, a power supply that's usually found in Phillips, Magnavox, Emerson, Element, etc.
My TV's particular model is ELEFW605, maybe that helps.
I don't know the background of the TV - I found it by my apartment's dumpster practically new in box - still had all the styrofoam, and a bunch of the baggies that the cables come in. No receipt though! One man's trash is another's treasure, so I decided to try and fix it.

I found this thread: https://www.badcaps.net/forum/showthread.php?t=48259
But for most of that thread, I believe people were using the documentation for BA3AU0F0102_2 so there was a lot of confusion. The poster whose problem that users were solving also changed, so I think that thread has run it's course.

I don't see any power LEDs or anything, and the power button doesn't do anything.
The top right transformer (T601) chirps about every 2 seconds when all output wires are hooked in.
When the ribbon cable (CN501) is removed, the chirping stops. It doesn't seem to matter if the bottom cable (CN1001) is plugged in or not (think it leads to the backlight?)

I read somewhere that a transformer making a sound indicates that something on the output side of the transformer is acting up. I tested diodes by desoldering one end, lifting it, and using the diode testing feature on my multimeter.

Good means they returned above 0.5, and a 1 in the other direction.
D655: Good
D653: Good
D650: Good
D1603: Good
D1605: Good

I also tested some of the components that they're selling in those 11-part repair kits.
D601: Good | D602: Good
D603: Good | D604: Good
D605: * | D606: * (Pliers too fat. Tested w/continuity meter, aren't shorted.)
D607: Good | D613: Good
Q601: Good | R618: Couldn't test, DMM resolution isn't high enough for 0.22Ohms
F602: Good

There's also a troubleshooting page for the PSU on the manual (pg 32) and I tested some of those. I omitted the repeats. Lots of these are surface mount, so I didn't desolder them and only tested continuity:
C625: Not shorted
C665: Not shorted (this one is a ceramic, but I didn't desolder it)
D617: Not shorted | D618: Not shorted
D621: Not shorted | D623: Not shorted
D664: Not shorted | IC601: Didn't test, but apparently must work or I wouldn't get voltages at the jumpers
IC604: Didn't test, not sure how

Was getting late - didn't get a chance to test these
Q602, Q603, T601, R630, R631

I also tested a couple of the jumpers at the top of the board while the ribbon cable was unplugged:
P-ON+21V: ~13V
AMP+13V: ~6.8V
ALL+3.3V: 3.3V

What is likely to be the problem, or where should I focus any component testing?
Please assume I'm an idiot - I'm a recent grad in computer science, not anything electrical.


Documentation:
Schematic: pg 48
CBA: Pg 66
Troubleshooting: pg 32

[dick_barton]

Re: BA3AU0F0102_3 PSU transformer chirps every 2 seconds

I would check the 3 x diodes, 1 x zener and 2 x capacitors connected to Pins 10+11, and Pins 14+15 of T601

[fubr]

Re: BA3AU0F0102_3 PSU transformer chirps every 2 seconds

Do you mean these?
D650 Diode
D653 Diode
D655 Diode
C651 Cap
C656 Cap
D654 Zener

[budm]

Re: BA3AU0F0102_3 PSU transformer chirps every 2 seconds

I also tested a couple of the jumpers at the top of the board while the ribbon cable was unplugged:
P-ON+21V: ~13V
AMP+13V: ~6.8V
ALL+3.3V: 3.3V

Those are correct readings for the P-ON 21V and the 13V when the PS-ON is not present.
You do not hear the chirp when the cable to the main board is not connected, right? If I remember correctly, some one found shorted cap on the main board.
You need to have the boards all connected and then check the resistance between GND and each Voltage output pins to see if any one of them show very low resistance.

[Alastair E]

Re: BA3AU0F0102_3 PSU transformer chirps every 2 seconds

That PSU looks like it was laid out by a three year old on ritalin--They Really ARE havin' a larf at our expense aint they!!

Appalling!

The electronics design aint much better--Parallel diodes recipe for eventual self-destruction, just like Vestel turds, instead of a Single diode correctly rated for the job...

[dick_barton]

Re: BA3AU0F0102_3 PSU transformer chirps every 2 seconds

Do you mean these?
D650 Diode
D653 Diode
D655 Diode
C651 Cap
C656 Cap
D654 Zener

Do you have the full schematic that you could share.

[fubr]

Re: BA3AU0F0102_3 PSU transformer chirps every 2 seconds

I also tested a couple of the jumpers at the top of the board while the ribbon cable was unplugged:
P-ON+21V: ~13V
AMP+13V: ~6.8V
ALL+3.3V: 3.3V

Those are correct readings for the P-ON 21V and the 13V when the PS-ON is not present.
You do not hear the chirp when the cable to the main board is not connected, right? If I remember correctly, some one found shorted cap on the main board.
You need to have the boards all connected and then check the resistance between GND and each Voltage output pins to see if any one of them show very low resistance.

There is no chirping when the ribbon to main board is disconnected.
I suppose I can poke around the main board too. Do I need to disconnect capacitors, or can I just use the continuity tester on my multimeter?

Do you have the full schematic that you could share.

Yes, page 48 for the schematic, and 66 for the Circuit Board Assembly



Thanks for the help!

[fubr]

Re: BA3AU0F0102_3 PSU transformer chirps every 2 seconds

That PSU looks like it was laid out by a three year old on ritalin--They Really ARE havin' a larf at our expense aint they!!

Appalling!

The electronics design aint much better--Parallel diodes recipe for eventual self-destruction, just like Vestel turds, instead of a Single diode correctly rated for the job...

For my own benefit, can you explain why parallel diodes are worse than a single diode? Is it because there's twice as much chance of failure?

Or maybe because real parts aren't ideal, and can have different forward voltages, so most of the current will go through the diode with a smaller forward voltage?

[budm]

Re: BA3AU0F0102_3 PSU transformer chirps every 2 seconds

Have all the connectors/cables in place, no power to the TV and then check the resistance between:
GND and ALL+3.3V
GND and AMP+13V
GND and P-ON+21V

[fubr]

Re: BA3AU0F0102_3 PSU transformer chirps every 2 seconds

Have all the connectors/cables in place, no power to the TV and then check the resistance between:
GND and ALL+3.3V
GND and AMP+13V
GND and P-ON+21V

GND and ALL+3.3V: 621 Ω
Gnd and AMP+13V: 1.68 kΩ
GND and P-ON+21V: 7.7 Ω

So uh, there's the smoking gun I guess?

I poked GND and P-ON+21V with cables disconnected and got a value between 20k and 50kΩ (well it said something like 50kΩ at first, and increased, then I probed again after a while, and it was around 20kΩ and increasing)

Tested these with a continuity meter too. They don't seem to be shorted , though D654 beeps for a split second? What does that mean?


Man, I hope the problem isn't on the main board. It doesn't look very fun to work with, what with so many surface mounts.

[budm]

Re: BA3AU0F0102_3 PSU transformer chirps every 2 seconds

Well, you have something bad on the main board that you need to trace it to see where that P-ON 21V goes to on the main board.

[fubr]

Re: BA3AU0F0102_3 PSU transformer chirps every 2 seconds

Well, I'm in it to win it I guess.

I don't think the earlier linked documentation is super helpful since it doesn't even have a model number, and there's just a schematic diagram. That main board is using DDR3 SDRAM, my board has DDR2.

Found a picture of the main board BA31T0G0201_3 online, and also have a picture I took of my own board.

http://assets.shopjimmy.com/media/ca...ma-001-top.jpg



Main difference I can tell between the two is that mine has a heatsink over IC3801

I'll keep looking for documentation, hoping to find a matching schematic.
Even if I can find a short, it's not really gonna help if I can't tell how to get a replacement.

budm, is there any chance you remember what thread it was on that some person found a shorted capacitor on their main board?
Edit: Actually I think I found it? https://www.badcaps.net/forum/showpo...&postcount=136

Edit2: Oh my god C3214 is actually shorted like citywidetvtech said. Though it looks like C3208 might be shorted too.
Now I really need to find the schematic

Edit3: Does IACWD mean anything to anybody? It's printed on top of IC3201, and google leads me to an MP1472GJ chip on AliExpress, which matches pg 60 of the documentation linked earlier
()
The Philips 49PFL3708 that the documentation is based on has identical IO to my Element, which leads me to think the main boards are verrry similar, with only a few minor differences like in DDR3/DDR2 ram


If that logic jump makes sense, then that means that documentation should work, and I can trust this schematic (on pg60 of the philips service manual):


But.. what units am I looking at? 0.1 and 4.7.... ____farads? nano? micro? pico? @_@

[budm]

Re: BA3AU0F0102_3 PSU transformer chirps every 2 seconds

Just remove one at time the suspect bad caps to see if the low resistance will go away first. They are .1uF and 4.7uF and they are connected in parallel.

[fubr]

Re: BA3AU0F0102_3 PSU transformer chirps every 2 seconds

D'oh you're right. Of course. Only one of them needs to be shorted for them all to appear shorted.

It was indeed C3214. After that was gone, pins 5 and 7 on IC3201 no longer test as continuous.

The resistance between GND and P-ON+21V goes into the 10kΩ range, too.
Thank you so much! Hopefully that was the only issue.

[budm]

Re: BA3AU0F0102_3 PSU transformer chirps every 2 seconds

You can solder in 4.7~10uF 50VDC lytics cap in place for testing purpose.

[fubr]

Re: BA3AU0F0102_3 PSU transformer chirps every 2 seconds

Haven't tested it yet, but I did replace the cap with a 4.7uF 35V SMT. This one isn't shorted

I was thinking and I realized that the TV only uses a 2 prong plug. Is there any reason why I shouldn't replace that entire wire with a 3 prong plug one, and connect the ground to the chassis of the TV?

[Alastair E]

Re: BA3AU0F0102_3 PSU transformer chirps every 2 seconds

For my own benefit, can you explain why parallel diodes are worse than a single diode? Is it because there's twice as much chance of failure?

Or maybe because real parts aren't ideal, and can have different forward voltages, so most of the current will go through the diode with a smaller forward voltage?

Current Hogging.

As they warm up, one will take more than the other--which leads to more heating--in that one, and more current flow in that one--while the other passes less current and cools and takes less cools more, so the hotter diode takes even more--gets hotter--till pop!

CRAP design by idiots--Or Accountants--Same thing--Idiots!!