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Jim Yanik

wrote in
:

On Thu, 7 Oct 2010 23:49:25 +0900, "Michael Kennedy"
wrote:

"Mark Zacharias" wrote in message
web.com...
"Michael Kennedy" mike@com wrote in message
...
Sorry if this is a bit of a novice question...

I have a SMPS in Plsama tv which upon powering up starts
clicking... It seems to do it as it warms up or the load changes on
the psu (screen going dark or getting light)

As far as I can tell it isnt any relay doing this, even though It
sounds like a relay.

Ticking alone I could live with, although a bit annoying but the
PSU also occasionally shuts down when cold. I am not 100% sure what
is clicking.. The clicking noise seems to be coming from different
locations at dfferent times, even possibly the X or Y sus boards.

I have sprayed the whole thing down with freeze spray to no
avail... It is built with PBF solder, so I guess bad solder joints
are likely issue also.

I have changed the obvious capacitors near heat sources excpet the
two large 400v 250uf filter caps.. Removed and checked the filter
caps and they checked good on my ESR meter.

Any Idea what would be clikcing? Here is the board layout
https://sites.google.com/site/chibamikey/PSU.JPG

I have seen similar issues on Samsung plasmas resulting from bad
solder connections at some switching transistors near the middle of
the board. The eyelets are too small and need to be scraped a bit to
enlarge them before resoldering. The board does look similar to
yours. Maybe you'll get lucky.
If not solder connections in there somewhere, failing capacitors
would be the likely culprit, although this problem has been much
more common on LCD sets. Plasmas I've seen don't seem to use the
really cheap caps.

Mark Z.

Thanks you suggested that before.. I will get a closer look at the
transistors and check out those eyelits.. I havent doent that yet, and
probably would have forgot had you not replied.

About the ticking.. It doesn't stop even with the power removed. It
is almost if something is expanding and contracting, but makes the
sound equilivant of a relay?!

The really strange part is it doesn't seem to come from one consistant
place..

Power removed or TV turned off? If it continues long after the set is
turned off (but still connected to AC power) it is something in the
standby power section of the main power supply.

If it continues for hours after the set is unplugged, it's probably a
cricket.

PlainBill

the ticking could be the PS current limiting and restarting:I've heard that
in lots of TEKTRONIX switchers. It should only last as long as the charge
in the mains filter caps.

--
Jim Yanik
jyanik
at
localnet
dot com