Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Transformer sound? OR transistor?

Status
Not open for further replies.

Kris668d

Newbie level 1
Joined
Jun 20, 2011
Messages
1
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,296
Hello. My TV just broke, and i cant find the spare part needed replaced which is a Vestel 17PW01-4.

So I have to replace the part on the board which is broken.. Unfortunately I dont know which part it is for sure. BUT a little transformer is making the traditional "hum" sound, which normally only old huge ones make. This transformer is very little and I have never experienced those make any sounds.

Transformer: smp-C2279 (Switch mode transformer & Line filter producer -- Shang Ming Electronics (SMP)??????-- Linearity coil, Choke coil,PFC,Clip inductor,SMT CCFL driving inverter, Silicon steel cores,Telecom transformer)
Why would this component be making this noise? Could it be broken, and why is the transformer making this noise?

BTW. On the PSU board there are other identical transformers, which dont make any sound..
Im asking, because it is hard for me to find another usable transformer, so I want to repair this part..

If not, could a transistor make any sound? Because there is 3 of them (Q816, Q282, and Q815) but it is hard to hear where excatly the sound is comming from at the PSU board.. And I dont want to move my head to colse to the board when it have a 230 Volts input:)

Thank you very much:):grin:
 

BradtheRad

Super Moderator
Staff member
Joined
Apr 1, 2011
Messages
13,647
Helped
2,701
Reputation
5,398
Reaction score
2,620
Trophy points
1,393
Location
Minneapolis, Minnesota, USA
Activity points
101,911
Apparently you're getting some kind of power but not the kind that makes the set work.

Since the transformer was quieter when the set did work, then it's now getting a noisy waveform which makes it hum or buzz.

Can you test the diodes in the power supply? See if one is open or shorted. That could cause a non-sine waveform through a transformer.
 

chuckey

Advanced Member level 5
Joined
Dec 26, 2010
Messages
4,863
Helped
1,308
Reputation
2,622
Reaction score
1,281
Trophy points
1,393
Location
Southampton and holiday cottage in Wensleydale (UK
Activity points
31,695
Most modern TVs use diodes and a capacitor to produce DC straight of the mains. This is then switched by transistors into a transformer which then produces various outputs which in turn are changed to different DCs to feed different circuits. So if any transformer is humming/buzzing it is because the first set of diodes are allowing AC through or the switcher is unstable because it should be running at 20KHz+ which you can't hear.
Frank
 

kevmic7

Newbie level 1
Joined
Oct 31, 2011
Messages
1
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,291
I've got this same problem and found that PL845 seems to be the cause of this issue! If you remove the PSU and lay it flat (upside down) the high pitch noise will disapear and the TV will work. If you disconnect this board and turn it upside down and back, you will hear something clunking:!: This is obviously some kind of switch that have broken and I do intend on removing PL845 to investigate it further. Very common problem with this model and cannot believe they haven't come up with a revised board:evil: Will let you know if it works for me.

My TV is now working perfectly in its present state. I have removed the 17LP01-4 PSU twisted it around so that it is more or less upside down and it's working :lol:
When I reposition the board back in place the problem re appears.

Now I've got to get rid of my shakes so that I can de-solder PL845 and see what the problem is behind the heat shield. Anybody gets there before me let me know what you find just encase I'm mislead.
 
Last edited:

Status
Not open for further replies.
Toggle Sidebar

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top