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Crumbtrail TV Forums: TV Equipment: TV Repair Forum:
32" Widescreen

 
 


andromeda
New User

Oct 5, 2005, 11:45 PM

Post #1 of 6 (1153 views)
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32" Widescreen Can't Post
A friend of mine gave me his 32" panasonic tx-32DK1 that didnt do anything apart from stay on standby. I have a multimeter, so followed the tracks, and found that the little solenoid type component was not making the circuit from the power in to the rectifier. This is suposed to have 12v DC on one side, and this seems as though it is powered by the small transformer which puts out 12v AC(this working). This is obviously rectified to 12v DC but this isnt getting to the solenoid component.

My questions are:
Are there any compnents that will fail easily that will cause this problem?
And I presume that this is some kind of safety circuit to cut the power. If this is the case what would control this safety circuit, and what would be the likely casue of the problem that I face?

Thanks in advance


(This post was edited by andromeda on Oct 6, 2005, 12:10 AM)



rrobor
Veteran

Oct 6, 2005, 12:28 PM

Post #2 of 6 (1144 views)
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Re: [andromeda] 32" Widescreen [In reply to] Can't Post
No its not a safety component as such, What you have is an LT stand-by power supply whose purpose is to supply 5V to the processor and the remote amplifier. On switch on this supply kicks the micro and the micro feeds a transistor which switches that solenoid on supplying power to the main supply. If on power up you dont hear 2 clicks from this solenoid the LT or micro is faulty. Check for LT after the transformer and diodes, could be 5 or 12V, likely faults to look for are faulty 3 pin regulator, open circuit primary on the transformer (internal thermal fuse) or the micro.


andromeda
New User

Oct 6, 2005, 4:33 PM

Post #3 of 6 (1137 views)
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Re: [rrobor] 32" Widescreen [In reply to] Can't Post
I do have an open circuit on the primary side of the transformer, although I am still getting 12v AC on the secondary side, which makes me thing that somewhere I'm measuring something wrongly. I will measure the diodes and regulator when I have a spare moment.


rrobor
Veteran

Oct 7, 2005, 10:44 PM

Post #4 of 6 (1130 views)
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Re: [andromeda] 32" Widescreen [In reply to] Can't Post
You are reading between primary and secondary, if there is no reading over the primary at all then its open and needs replacing. The other thing that may happen is that as the transformer has mains voltage across it, if the break is on the earthy end of the winding there will be a reasonably high capacitance value from primary to secondary, this may be upsetting your meter and giving you a fantom reading.


andromeda
New User

Oct 8, 2005, 12:51 AM

Post #5 of 6 (1127 views)
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Re: [rrobor] 32" Widescreen [In reply to] Can't Post
I removed the transformer and checked it on resistance, rather than 'beeper' The primary to primary on the transformer has a reading of 3.6Kohms, whereas the secondary side have a reading of close to 0 ohms.
Their are some very small diodes that measure short both ways while in situe, but I've yet to take these out to measure them properly. The solenoid thing seems to come from a big chip with hundreds of legs, and the other side is to the transformer through a couple of resistors and diodes.

If it is this chip thing, then i presume that it is landfill. Also, what is the solenoid thing for? if it a kinda cut off thing, then will I be able to short the 2 pins and skip the solenoid, to make it work?


rrobor
Veteran

Oct 8, 2005, 8:21 AM

Post #6 of 6 (1122 views)
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Re: [andromeda] 32" Widescreen [In reply to] Can't Post
I believe you are a bit out of your depth, I believed i explained the solenoid was to switch the set on from stand-by. the small transformer supplies power to a low tension supply which feeds the control chip and the remote receiver. Your transformer is OK, it seems a wee bit high in resistance but think its OK. So read the secondary diodes and kill the beeper. If any read short lift one end and try again. Chances are your diodes will be OK and you got a piddly little bypass capacitor short. Shorting the relay contacts will tell you everything or nothing, if the micro relies on a feed from the LT transformer then you have not advanced any further. If not then yes, the set will come alive.

 
 
 


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