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problem with Sanyo DP32746
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PostPosted: Fri May 30, 2008 9:25 pm    Post subject: problem with Sanyo DP32746 Reply with quote

I was given this TV because it quit working. I was told it was working fine for about a year and then one day it the picture suddenly went out. If I power it up, the screen briefly flashes and goes dark. The sound works fine, but there is no picture at all. It appears the CCFT's are not lighting up. I checked the power supply board, and it seems OK, and I have power at the CCFT driver board, but I do not have the 1100V present to drive the tubes. There are several tubes and each one appears to have a separate driver circuit and transformer on the board, so I doubt they are all bad. Could this board be the problem or could it be another board that controls or modulates the HV output from the driver board? Without a schematic, I am pretty much flying blind, and I am at a loss on what to check next. Also, where can I find a schematic for this set? Thanks in advance for any help.
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minnie



Joined: 18 Aug 2005
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PostPosted: Fri May 30, 2008 9:56 pm    Post subject: Reply with quote

One of three possibilities. The T-con board is bad, the inverts are bad, or a bad panel. You can check F100 on the inverter to see if it is the inverters. Otherwise now much do you want to spend.
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PostPosted: Tue Jun 03, 2008 6:35 pm    Post subject: Re:problem with Sanyo DP32746 Reply with quote

I checked out the set again today. If I shine a bright flashlight into the screen at an angle, I can see pixels and movement, so I think the panel is ok, however, I suspect there may be a problem in the inverter board as I checked F100 on the inverter board as you suggested, and it appears to be open. Unfortunately, I do not have any fuses like these, so I am going to temporarily bypass it with a fuse at or close to the rating on the SMT fuse and see if the screen lights up. If so, then I will see about obtaining the proper replacement fuse. I am wondering though as to why the fuse blew in the first place( possibly a shorted winding in one of the inverter transformers? ) and if a replacement fuse will also blow when I energize the circuit. I am going to investigate the problem further, and will let you know what I find out. If I find the problem is definitely the inverter board, then I will try to repair it if I can locate the bad component(s) and replacements for them, if not, I will just replace the whole board. I was told that the TV was purchased new for about $800, and it was only used about a year before it went down, and sat in a corner of the room for about another year before it was given to me, so I am willing to spend up to a couple hundred dollars or so to fix it, as I would still have to spend way more than that to buy a comparable set new.
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minnie



Joined: 18 Aug 2005
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PostPosted: Tue Jun 03, 2008 7:50 pm    Post subject: Reply with quote

If the fuse is open you can try to replace it. It will blow again. Sanyo's #800-877-5036.
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PostPosted: Wed Jun 04, 2008 2:58 am    Post subject: Re: problem with Sanyo DP32746 Reply with quote

I bypassed the fuse temporarily with a GMA fuse of the same rating for test purposes. It blew as soon as I energized the circuit. I also bridged the fuse with a 28v aircraft lamp I had laying around which draws about 2 amps when operated at 12v. I figure it pulls about 4 or 5 A at 24v, so I figure it would supply enough current for testing, but not enough to burn anything up. When I power up the lamp comes on at full brightness, so apparently there is a short somewhere, but I haven't been able to locate it. I don't see or smell any smoke nor do I see any burnt traces or components. I checked the filter capacitors and they seem okay. The rest of the devices are all tiny little SMT's with the exception of the transformers, so it would a real hassle to remove any of them to track down the shorted branch. I do have a lower resistance on the primary windings of several of the transformers(about 49 ohms versus about 116 ohms for the rest of them) on the side of the board supplied from the blown fuse, but I am stumped as to where the short actually is. I am now trying to locate a source for another board. I called Sanyo, but couldn't reach them(I think they were closed for the day as it was about 5 when I called), so I e-mailed them and asked them about obtaining a board. So, hopefully in a day or two I should hear from them.
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vtech



Joined: 08 May 2006
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PostPosted: Wed Jun 04, 2008 5:33 am    Post subject: Reply with quote

Most common failure in the inverters are the fets/mosfets which may damage the driver txformers(s).
Don't waste time trying to repair unless you have experience & access to parts.

Googling your model number pulls several suppliers of boards
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PostPosted: Fri Jun 06, 2008 2:28 am    Post subject: Reply with quote

Upon further investigation, I determined that two of the chips(I guess these are the mosfets you are referring to) that drive the transformers are shorted. It seems they are in parallel, so I am not sure if it is one or both of them without removing them and testing them out of circuit. I have been unable to find a replacement chip, and I don't have a spare board to use or pull parts from. I called Sanyo, and they told me they don't sell the chips separately, that I would have to replace the whole inverter board, so it is pointless trying to replace the chips, and they are so tiny I really don't want to go through the hassle of replacing them anyway, so I am just going to order a replacement board and be done with it.
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minnie



Joined: 18 Aug 2005
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PostPosted: Fri Jun 06, 2008 4:33 am    Post subject: Reply with quote

You got the point. This day and age it's board replacement. It's BS. They don't even make schematics for half the stuff anymore.
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PostPosted: Mon Jun 16, 2008 7:59 pm    Post subject: Re: problem with Sanyo DP 32746 Reply with quote

I ordered a new inverter board last week and just got it today. I installed it and powered up the set and now the screen lights up and everything is working fine. Thanks for pointing me in the right direction! Very Happy
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vtech



Joined: 08 May 2006
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Location: USA

PostPosted: Mon Jun 16, 2008 10:27 pm    Post subject: Re: problem with Sanyo DP 32746 Reply with quote

new user wrote:
I ordered a new inverter board last week and just got it today. I installed it and powered up the set and now the screen lights up and everything is working fine. Thanks for pointing me in the right direction! Very Happy


Not too bad to get a 32' LCD for a little troubleshooting & the price of a board eh? Very Happy
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