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Toshiba SD-P7000 No sound

 
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efilnikufecin



Joined: 11 Aug 2008
Posts: 22

PostPosted: Wed May 02, 2012 7:08 am    Post subject: Toshiba SD-P7000 No sound Reply with quote

This is a LCD TV/DVD combo unit which had no sound when I obtained it. I just programmed a remote using the Toshiba 19LV505 TV-DVD upgrade, and all the functions I have checked work except the audio button. I have tried headphones and the built in speakers. When tuned to a station which has no signal I can faintly hear static from the speakers which leads me to believe that there is probably a blown capacitor or 2 in the audio amp circuit. My problem is that I cannot get the thing apart.

I have removed all the screws, and started in the lower right corner (DVD player side) prying the clips loose, but as I go I start to see a circuit board inside flexing badly as if it is connected to both the front and back panels. I don't want to proceed with this method unless it is a last resort for fear of breaking the board, and rendering the whole set useless. So I was wondering if anyone here has taken apart this model of TV, and might be able to point out where I am going astray? I am not even getting to the first corner. I have tried the other corners, but cannot seem to get it started on any of them.
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zaphod7501



Joined: 02 Aug 2004
Posts: 528
Location: Peoria Illinois

PostPosted: Wed May 02, 2012 10:15 pm    Post subject: Reply with quote

Sight unseen, I can only offer guesses - but - on some of these sets the back doesn't come off first, the front trim does. Then additional screws are revealed that attach the panel to the back cabinet. So, when you are prying the clips, see if the front is separating from the panel.

There are no service manuals that I have seen, for the most part, since these were never repaired by the manufacturer, just exchanged.

Before tearing the set apart, make sure you check all of the menu settings. Especially things like speaker on/off, Stereo/SAP settings, fixed/variable output settings. Also, if you are using a cable box, digital converter, or satellite receiver, remember that those boxes also have volume controls. Check it also with other external sources like DVD, converters, etc in order to verify the problem is actually in the set not the source.
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efilnikufecin



Joined: 11 Aug 2008
Posts: 22

PostPosted: Sat May 26, 2012 5:09 am    Post subject: Reply with quote

The project went on the back burner for a while. Now I am back on it.

Updates on where I am at:

No menu option changes allowed sound.

I figured out how to open the case.

Hooking a wire between the headphone jack, and my high output home stereo I found that if I turn the stereo up to almost full blast I get sound, but with an annoying humming noise that is louder than the sound. The humming noise is likely a side effect of turning my receiver up so high, I had never done that before especially with the input plugged into a headphone jack of anything.

When hooking AV cables from the RCA outputs to my TV I use I get sound and video on my other TV when playing A DVD only. The video out plug is marked DVD only and I assume the audio out is the same.

I have found a PDF service manual for the TV, and discovered that it uses separate mps7720 audio amp chips for the left and right sound output. I was unable to find a datasheet on the mps7720 audio amp chip, however I did find a data sheet on an mp7720 audio amp chip. The data sheet has MPS all over it as if MPS is the manufacturer. The circuit shown for the typical application of the mp7720 chip appears to almost be a duplicate of the circuit diagram shown in the service manual, but the diagram in the service manual shows some extra components. I am wondering if anyone can verify that the mp7720 and mps7720 chips are in fact identical chips, or may be able to locate a mps7720 data sheet. I am thinking they are not identical because the data sheet shows the mp7720 chip to be 20 watts, but http://www.mediacollege.com/equipment/toshiba/tv/lcd/sdp7000.html indicates the audio output of the TV to be 3 watts per channel.

page 31 of the service manual shows a Toshiba part number of AF500060 and an LG part number of 0IMCRMZ002A for the chip. There is a circuit diagram for the audio amps and muting circuit on page 40

Service manual: http://cmac.uarts.edu/equipmentroom/inventory/manuals/sdP7000sm.pdf page 40 has a diagram of the audio amp circuit.

datasheet for mp7720: http://pdf1.alldatasheet.com/datasheet-pdf/view/189187/MPS/MP7720.html
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