Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1   Report Post  
Jason D.
 
Posts: n/a
Default Interesting experience with Citizen 19" chassis.

Customer complaint: no vertical. Fine the usual fix repair vertical
circuit for small estimate and got that OK'ed.

Got vertical fixed as usual, huh? B+ is jammed at 200V not 115V (this
is SMPS), replaced the NPN small signal transistor in cold side
feedback regulation circuit (measured OPEN on all 3 legs). Got 115V
back and ran it on test wondering why I have good voltages except I
haven't checked HV, that pic is bit dimmer and bit "blown up" as in
oversized picture in small bezel.

Then cinched the puzzlement: finally flyback failed, YOWCH! flyback
core HOT! That HOT transistor didn't bat an eye, was running good
temperatures. Now I know why! The high B+ happened to kill vertical
circuit first with too high voltage but also damages flyback
transformer enough in the process.

This explains why I see number of HV blocks (205064) failures because
of high B+ while in standby. And exiting standby to run voltage was
zapping block eventually HV block failed.

Gonna watch out for high B+ especially if customer left TVs running
quite awhile with high B+! Many Citizen chassis didn't shut down on
high B+ which is bothering me as most TVs even cheapest ones does cut
out in seconds up to a minute.

Cheers, Wizard
Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Grizzly 6" Jointer Experience Pradeep Gupta Woodworking 22 March 28th 04 07:59 PM
HF 34706 lathe Dominic Palazzola Woodturning 56 March 8th 04 11:21 AM
seeking manufacturing engineer with liquid reservoir transdermal patch experience Rick Walker Metalworking 0 September 15th 03 04:00 PM
Stripped doors in Edinburg (experience; long) robin UK diy 0 September 1st 03 01:49 PM
The Grizzly Experience George Woodworking 3 July 24th 03 03:00 PM


All times are GMT +1. The time now is 05:17 PM.

Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 DIYbanter.
The comments are property of their posters.
 

About Us

"It's about DIY & home improvement"