I’ve got a couple “big” TVs in the FROG but shipping would probably be killer
--FT Sent from iFōn > On Feb 11, 2024, at 5:52 PM, Jim Cathey via Mercedes <mercedes@okiebenz.com> > wrote: > > The cabin's CRT TV crapped out last month, and I had my son bring it > home. Zenith model B25A11Z. He said the vertical deflection shrank > down, and then there was a loud noise, black screen, and bad smell. I > don't want anything newer down there, as this one's nearly theft > proof, so I'd like to fix it (myself) if possible. > > I found a schematic of the TV, enough to look at, anyway. There is a > big power transistor in the horizontal drive, and in-circuit probing > with the Fluke DMM shows a B-E short, which cannot be good. 2SD2499, > which is a Horizontal Output Transistor. (Which means a certain class > of specs, along with an internal flyback diode and a biasing > resistor.) I can get 10 of them from China for about $5, so I ordered > them. Shipping to be slooooow... > > I replaced the HOT, but that did not fix things. I got the Variac > hooked up, and brought in an oscilloscope and a DMM. Running > relatively low (25V) line voltage, for safety, showed that the 140V > output of the SMPS was working, and the +5V logic supply was good. > So, things are sort of working. I could hear the speakers gently pop > on and then off when the power button was pressed. I could see the > base drive of the HOT go on briefly when started, but after less than > a second it shuts off again. > > Probing around showed no voltage at all on the output windings of the > flyback transformer, and only then did I notice the giant crack in its > housing! Burned, and split. So, that's where the magic smoke had > come from! I had been looking for physical damage, I don't know how I > missed that one. The TV's CPU is looking for flyback output voltages > at startup, and seeing none it shuts the horizontal drive down for > safety, and to prevent further damage. > > So, I need a new flyback, if I want to fix this thing. 95-4601-01. I > found one for sale online, at $50 plus shipping. I think... not. An > alternate shown on the schematic is 95-4372-01; I found one of those > and made a $5 (plus shipping) offer on it. It might not even work, > and I might not get it. This is starting to look pretty unattractive. > > Or... there was a $20 Panasonic TC-P50G15 (8/2009) plasma TV on > Craigslist, with remote. (But no stand.) An infinitely better TV, > and certainly cheap enough, but big, heavy, and much more attractive > to thieves---who would probably not recognize its lack of commercial > value from afar. I bought it anyway. > > Those Panny plasmas are _very_ nice TV's, we have three of them already. > (The first one was $1100 new, almost the same model as the $20 one.) > > -- Jim > > > _______________________________________ > http://www.okiebenz.com > > To search list archives http://www.okiebenz.com/archive/ > > To Unsubscribe or change delivery options go to: > http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com > _______________________________________ http://www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
