The Great Pumpkin Leaves Us A 42" Toshiba - Page 1
Forum section: electronics / repair

author: SgtRock
author_rank: Unknown
timestamp: December 01, 2014, 12:17:33 pm
content: Greetings EEVBees:--My brother got back from the store about 6pm EST yesterday. He had found on the curb this, see below, Toshiba Rezga42RV530U made in June 2008. I plugged it in and joy of joys, no power light, always a good sign. In perfect shape, but of course no remote.--I took the back off, confirmed 120V AC in, but had no DC voltages any where on the cables coming out of the PS Board. So I pulled the PS Board, and found no 170V output from the bridge. Turns out the 1.8 Ohm 5W WW Ceramic, went completely open, showing no damage, as you can see. I Paralleled one up from the junk box, using 5.6 and 2.7 as seen below. Now I had 5V and 3V but no 12 or 24, because the PS was not yet turning on. I could not figure out which pins to short to get it to fire, so I just installed it, and gave it the smoke test, and it is working perfectly in all respects. Bob is your uncle. So the Great Pumpkin has come through again. I wonder what we will find at the curb towards the end of the year."A three legged dog goes into a bar and says "I'm looking for the man that shot my paw"Jim Varney 1949 - 2000Best RegardsClear Ether

author: tom66
author_rank: Super Contributor
timestamp: December 01, 2014, 01:28:22 pm
content: Nice fix. Looks like an in-rush precharge resistor. If improperly sized these can fail due to the large inrush current.A quick approximation: If the relay clicks on at 170V mains peak, the peak power dissipation in the 1.8 ohm resistor will be 16kW!!This sounds a little high, so are you sure it is not an 18 ohm resistor? Which would dissipate ~1600W, still high but perhaps manageable for a pulse?Make sure whatever resistors you use are rated for inrush / pulse duty.

author: retiredcaps
author_rank: Super Contributor
timestamp: December 01, 2014, 05:38:03 pm
content: Good job on the diagnosis. I wonder how many other sets will be sitting outside on trash day with Black Friday and Cyber Monday sales in the USA?Maybe cruise in the more up$cale neighborhoods/zipcodes?

author: SeanB
author_rank: Super Contributor
timestamp: December 01, 2014, 06:51:02 pm
content: 1R8, though you could have just left the 2R 7 in there, it will not make a difference at all in operation, just lower the surge a lot. Ideally you need to replace the resistor with the appropriate fused resistor as this is a safety part, designed to fail. Me I would put a PTC thermistor in series with the 2R7 device instead. Old one from a scrapped PC power supply is best.

author: SgtRock
author_rank: Unknown
timestamp: December 01, 2014, 10:40:09 pm
content: Greetings EEVBees:--Well she is still up and running. I want to thank everyone for the good advice. It is only due to the good efforts of DJ, RetiredCaps, Tom66, and others that I know enough to repair the odd junker. I have ordered a remote from here in the US for $15. I have also as per advice by Tom66, SeanB and Wilfred ordered a 2 Ohm 5 Watt fusible, which is apparently the recommended replacement. Link below.http://www.ebay.com/itm/141186414306--And yes the curb and dumpster patrol will be conducting nightly raids, with more frequency as the Holidays approach. If we had not gotten to this TV first, likely it would have been chopped up for $4 in beer money."Does not squirrel crack nuts on bough of oak tree."Lao Fu 1411 - 1623Best RegardsClear Ether

author: denelec
author_rank: Regular Contributor
timestamp: December 01, 2014, 11:27:23 pm
content: Quote from: SgtRock on December 01, 2014, 10:40:09 pmGreat repair. It's always a good feeling when you can bring a (left for) dead device to life.Lao Fu 1411-1623??? This fellow sure had a long life!

author: SgtRock
author_rank: Unknown
timestamp: December 02, 2014, 12:09:27 am
content: Greetings EEVBees:--Verily Brother Jones of the Order of Leibowitz hath told us that the First Commandment is "Thou shalt take voltages!" That is almost all that was necessary in this case. After the 170VDC went missing is was a simple straight up murder hunt. Fu did live a long life. I hear Wun Hung Lo's father Tu lived to be over a hundred.Come, let us hasten to a higher planeWhere dyads tread the fairy fields of Venn,Their indices bedecked from one to n...Stanislaw Lem 1921 - 2006Best RegardsClear Ether

author: SeanB
author_rank: Super Contributor
timestamp: December 02, 2014, 04:51:40 am
content: Good that you are reusing instead of scrapping. Saves the planet and such.

author: Yago
author_rank: Frequent Contributor
timestamp: December 02, 2014, 08:51:54 am
content: Quote from: SeanB on December 02, 2014, 04:51:40 amGonna try and get some Sets from town recycle centre, thing is I suspect it is illegal in some way now in UK!Bet I have to fill in lots of forms!!Well won Sgt!

author: EEVblog
author_rank: Unknown
timestamp: December 02, 2014, 09:47:26 am
content: Nice fix