Good day folks. Got this Sharp LC-32S7E TV which is pissing me off: can't possibly figure out what's wrong with it, although I have some ideas. I've attached the schematic for the power supply, a 715g3467, although for some reason it doesn't include the PFC circuit, even though the board has it. When I got it, IC931 was blown apart (to the right of the schematic - you can also use CTRL-F). It's a TNY277 according to the schematic, but I decided to put in a TNY280 just to increase the maximum current a bit. I'm not sure if it was the right thing to do though, because the board still doesn't work: I get nothing on the secondary. Have a look at the datasheet for those TNY chips, perhaps there's some major difference between 277 and 280 which prevents it from starting up that I'm not seeing. One theory of mine is that transformer T901 has gone open circuit: I noticed that I get no continuity across pins 1-2 of transformer T901. USUALLY, on other supplies, the resistance of such a primary winding is low enough to cause my meter to beep, but here I get nothing, which of course doesn't necessarily mean the transformer is bad. If you look closely at the schematic, there's no protection for IC931 - the S pins are tied directly to GND, meaning that when that chip shorted D-S and blew up, it might've taken out the transformer with it, since the 2 mains fuses were also OK when I got it, which only makes me wonder exactly what happened. I get around 316v on the main cap, but nothing on the AUX winding after D981. Interestingly, if I lift the cathode leg of the D981 from the board, I do see 11-12v on it. Solder it back in and I get nothing, so I'm still thinking perhaps the IC itself is not the correct one....I HATE PSUs that think they're being cutting edge by employing all-in-one sh*t chips like these- just have some damn FETs that blow and can be replaced, not this 1-piece bullshit that never seems to want to work...damn....Anyway, enough of my rants. Has anyone repaired this type of Sharp before ? Cheers.
Thank you to the guys at HEGE supporting Badcaps [ HEGE ] [ HEGE DEX Chart ]
Announcement
Collapse
No announcement yet.
Sharp LC-32S7E dead power supply (no STBY).
Collapse
X
-
Re: Sharp LC-32S7E dead power supply (no STBY).
I do not see the schematic. What DCV do you have on the Drain pin of the TNY SMPS IC? The OPTO for the feedback may be damaged also when the IC blew up.
"just have some damn FETs that blow and can be replaced," but 99% when MOSFET shorted out with Drain to Gate, it will take out the SMPS IC with too, and if you take a chance by not replacing the IC then you may take out the new MOSFET due to failed SMPS IC.Last edited by budm; 06-09-2017, 09:14 AM.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
-
Re: Sharp LC-32S7E dead power supply (no STBY).
Pff...yeah, epic fail. Forgot to upload the schematic too...overworked....anyway. As far as I remember, I get 0v on the D pin (with respect to my negative probe on primary GND). The opto IC doesn't appear to be shorted (i.e, I only get a voltage reading in one direction with my meter in diode mode).Attached FilesWattevah...
Comment
-
Re: Sharp LC-32S7E dead power supply (no STBY).
The receiver side (Photo Transistor) should not show any conduction, that Transistor will conduct when LED sender side is ON.
If the Drain pin shows 0V then that confirm there is no continuity on the primary winding (open circuit) of the transformer.
Q931 could also be damaged also since it is in parallel with the OPTO.Last edited by budm; 06-09-2017, 10:07 AM.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
Comment
-
Re: Sharp LC-32S7E dead power supply (no STBY).
Originally posted by CapLeaker View Postthat sux... maybe there is a thermal fuse inside the transformer?Wattevah...
Comment
-
Re: Sharp LC-32S7E dead power supply (no STBY).
Puzzled. You said you lifted one end of the diode and you have a voltage. If this is the case then the transformer primary must be OK. If it was open circuit there would be no conduction Pins 1 - 2 so you would not have any voltage induced in the winding between pins 4 & 5
Are you certain it's the same schematic for the power supply or is the transformer wired up differently?Last edited by dick_barton; 06-09-2017, 10:19 AM.Willing to help but I'm no expert.
Comment
-
Re: Sharp LC-32S7E dead power supply (no STBY).
Originally posted by dick_barton View PostPuzzled. You said you lifted one end of the diode and you have a voltage. If this is the case then the transformer primary must be OK. If it was open circuit there would be no conduction Pins 1 - 2 so you would not have any voltage induced in the winding between pins 4 & 5
Are you certain it's the same schematic for the power supply or is the transformer wired up differently?Wattevah...
Comment
-
Re: Sharp LC-32S7E dead power supply (no STBY).
" if I lift the cathode leg of the D981 from the board, I do see 11-12v on it." So you are seeing the Voltage at the Cathode of the diode which is lifted off the board, correct? or you are seeing the Voltage at the pad where the Cathode WAS connected to?Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
Comment
-
Re: Sharp LC-32S7E dead power supply (no STBY).
Originally posted by budm View Post" if I lift the cathode leg of the D981 from the board, I do see 11-12v on it." So you are seeing the Voltage at the Cathode of the diode which is lifted off the board, correct? or you are seeing the Voltage at the pad where the Cathode WAS connected to?Wattevah...
Comment
-
Re: Sharp LC-32S7E dead power supply (no STBY).
Originally posted by Dannyx View PostAt the cathode - after the diode that is.
And for sure you also DO NOT see any Voltage at all on the Output side?Last edited by budm; 06-09-2017, 01:53 PM.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
Comment
-
Re: Sharp LC-32S7E dead power supply (no STBY).
Originally posted by budm View PostWell, that made no sense period if the Transformer has open primary circuit and you also verified that there is no Voltage at all on the Drain of the IC. When something does not make any logical sense then it has to be an error in measurement some where.
And for sure you also DO NOT see any Voltage at all on the Output side?Wattevah...
Comment
-
Re: Sharp LC-32S7E dead power supply (no STBY).
Hi Dannyx, first post here.
First of all, forgive my bad english to the forum. I wish to add that this power supplies have much fails on this transformers.
In my experience i had a 715T3150-3 from a Sharp LC-42SB45UT with similar failed components (TNY277PN) and the stand-by chopper transformer T904, P/N: 060TL42T916L.
Symptom: Dead supply, even stand-by voltage. Just having 310v on the main capacitor.
Visual obs: IC903 dead (exploded as you can see).
Procedure: IC903 replaced, and for pracautions primary recaped. After plug in, make no differences.
In a depth observation, i saw that T904 has open circuit (see the red line in the schematic).
From this diagnose, i decided replace the complete board, and now works great.
I hope that this can guide your diagnose and solve your problem.
Greetings from Chile.
Comment
-
Re: Sharp LC-32S7E dead power supply (no STBY).
Originally posted by skynetronics View PostHi Dannyx, first post here.
First of all, forgive my bad english to the forum. I wish to add that this power supplies have much fails on this transformers.
In my experience i had a 715T3150-3 from a Sharp LC-42SB45UT with similar failed components (TNY277PN) and the stand-by chopper transformer T904, P/N: 060TL42T916L.
Symptom: Dead supply, even stand-by voltage. Just having 310v on the main capacitor.
Visual obs: IC903 dead (exploded as you can see).
Procedure: IC903 replaced, and for pracautions primary recaped. After plug in, make no differences.
In a depth observation, i saw that T904 has open circuit (see the red line in the schematic).
From this diagnose, i decided replace the complete board, and now works great.
I hope that this can guide your diagnose and solve your problem.
Greetings from Chile.Wattevah...
Comment
-
Re: Sharp LC-32S7E dead power supply (no STBY).
Originally posted by Dannyx View PostThat's exactly what I'm getting as well (though the schematic is ever so slightly different from yours - mine is T901 instead of T904, but the circuit is identical). I presume you no longer have the functional board on hand to measure pins 1-2 of T904/1 to see if you're indeed getting continuity, or perhaps you remember taking such measurement and telling me the results...guess I'll have to swap the board also. That's what you call bad design, when the power IC takes out the transformer, one of the most crucial components to any SMPS since it's not like you can run to your radioshack and get a bunch of these - once it's gone, the whole board goes in the trash.....dumbasses.....:|Last edited by skynetronics; 06-10-2017, 10:22 AM.
Comment
-
Re: Sharp LC-32S7E dead power supply (no STBY).
Originally posted by skynetronics View PostYep, i remember the measurement. I had no continuity between 1-2, but between 1-3, was ok. On the schematic that i attached, the red line represents the open of the coil on that chopper.Wattevah...
Comment
-
Re: Sharp LC-32S7E dead power supply (no STBY).
Originally posted by Dannyx View PostYes, that I understand, but I was asking about the functional replacement board. Did you measure that one as well and indeed got continuity between 1 and 2 as well ?
Comment
-
Re: Sharp LC-32S7E dead power supply (no STBY).
Originally posted by skynetronics View PostYes, on the functional replacement board i remember that have continuity on that chopper (on 1-2, and 1-3).Wattevah...
Comment
Comment