I'm servicing a Daewoo DTQ-27S2FCV television. The HOT and switching
regulator transistor were shorted. I replaced the HOT with an RCA sub but
still stamped with the original part number, 2SD1880. I replaced the
regulator with an NTE 379 which is a sub for an E13009-2. The set powered up
fine with a great picture. A half hour later, same parts shorted out again.
I decided to order the original parts from Daewoo and have now received and
installed them. I monitored the collector of the HOT and it appears to be a
nice clean pulse. The temperature of the HOT is another story. After about
10 minutes, it climbed to 150º F (66º C) and I turned off the set to post
this message. A blurb in Sam's FAQ
http://www.repairfaq.org/REPAIR/F_monfaqi.html, section 14.12) says that a
temperature of over 130º F (54ºC) is cause for concern. The datasheet for
the 2SD1880 says the operating junction temperature, Tj is 302ºF (150º C).

I fondly remember monitoring those STRS6301 switching regulators in the
older Sony sets and making sure those would stay under 160º F (71º C) but I
really haven't considered using the temperature of a HOT as a
troubleshooting technique until now.

Thanks for your reply.

--
David Farber
David Farber's Service Center
L.A., CA