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Sony Trinitron KV-27TS27    
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SoCalRocker



Joined: 28 May 2008
Posts: 5

PostPosted: Wed May 28, 2008 5:42 am    Post subject: Sony Trinitron KV-27TS27 Reply with quote

Received this TV free, picture is crisp, color still vivid, and had very few hours on it from the previous owner..

The right side audio isn't working. Opened unit and swapped left leads to right speaker, speaker works (rules out blown or damaged speaker). Right audio cable has continuity end to end, so cable appears good. Checking voltage on left output shows good and variable voltage, next to nothing for right side.

Advice? Does the SBX1637 board issue apply if only one channel goes south?

Thanks in advance!

- Keith
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kuhurdler



Joined: 28 Dec 2006
Posts: 2879
Location: Overland Park, KS

PostPosted: Wed May 28, 2008 11:08 am    Post subject: Reply with quote

it would be at the top of my list, but I couldn't say for certain.

make sure the TV is set to stereo, and not mono.
Jesse Mack



Joined: 22 May 2008
Posts: 600
Location: The Last Frontier

PostPosted: Wed May 28, 2008 11:30 am    Post subject: Audio Problem Reply with quote

Keith,

This unit uses a basic audio output circuit consisting of an TBA2009A IC1400 Audio Amplifier. Since I can assume you have only a multimeter for troubleshooting, (checking voltage on outputs??? there is only RMS going to speakers) you are somewhat limited with what you can do.
However, that being said, Check the "DC" levels on pins 8 and 10 of the output IC 1400. It should be approx 10.7 VDC. Without an Oscope you cannot check the RMS input to this IC due to the levels being much, much to low. If you have access to a color bar tape (the old VHS style) you can use the audio tone on this tape to troubleshoot levels. It is very difficult, to say the least, to use "over the air" sound when troubleshooting audio circuits. The sound is in stereo and the levels and content are different. You you wish, you could swap capacitors C1418 and C1419 to see if the problem switches sides. These are the coupling capacitors and they tend to dry out with age and this set is definately not short on age. :P If you check the RMS just before the capacitors and find it is normal the capacitor would be bad.

Hope this helps.

Jesse
SoCalRocker



Joined: 28 May 2008
Posts: 5

PostPosted: Wed May 28, 2008 8:38 pm    Post subject: Reply with quote

Thanks for the replies folks -

@kuhurdler

I can access the TV config through a Uni Remote, and the problem exists in both stereo and mono. The curious things is, even if the tuner is set for mono, when you use the external video inputs for a DVD player, it does not mix the incoming audio to mono.

@Jesse

Voltage at IC 1400 is as follows:

post 8 - + 20.8 VDC
post 10 - + .013 VDC

verified using several diff ground sources

Have not had time to swap CAPs. This aren't expensive, are they? Instead of swapping, shouldn't they just be replaced if you're going to desolder them to begin with?

I removed card A and examined the SBX1637 module. From the backside, it seems rather apparent this module was either replaced or re-soldered... and I've seen a LOT better soldering jobs. The module itself has a Sony stamp on it, so it's an original Sony 1637. Now I'm left with a new variable - is that solder job causing a problem? I have no idea how to check all of those circuits to make sure they are sound. I have to find my magnifying glass to have a better look at those solder joints to see if any are shorting.

As a side note, I removed all cards and completely cleaned all of them and the main board. Everything's nice and clean. I disconnected and re-connected every board connection and put it all back together. No worse, no better as far as the right channel audio.

Any further ideas welcomed. Thanks again!

- Keith
Jesse Mack



Joined: 22 May 2008
Posts: 600
Location: The Last Frontier

PostPosted: Thu May 29, 2008 12:57 pm    Post subject: ic1400 Reply with quote

With that kind of DC levels the IC is most likely bad.

If you decide to change the IC be sure to acquire some
desoldering tape as Sony foils are fragile and the desoldering tape will make the job much easier.

Jesse
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SoCalRocker



Joined: 28 May 2008
Posts: 5

PostPosted: Thu May 29, 2008 2:53 pm    Post subject: Re: ic1400 Reply with quote

Jesse Mack wrote:
With that kind of DC levels the IC is most likely bad.

If you decide to change the IC be sure to acquire some
desoldering tape as Sony foils are fragile and the desoldering tape will make the job much easier.

Jesse


Thanks Jesse. Found the amp locally for under $5, so I'll pick it up tonight and throw 'er in. I use a solder pump and desoldering braid, ao hopefully that will work out for me. I'll update when possible. Appreciate the help!

- Keith
SoCalRocker



Joined: 28 May 2008
Posts: 5

PostPosted: Thu May 29, 2008 10:41 pm    Post subject: Reply with quote

Bought the Amp, and the CAPs. Replaced all, no joy.

Voltage with new IC:

Post 8 - + 20.95 VDC
Post 10 - + .0113 VDC

I am in the process of desoldering out the SBX module. Those are some extremely small posts to work with. Have it out now, and cleaned up the traces. Seems to be some damage to the trace around post #7, which apparently is supposed to go to the SAP LED. Looks like the schematic has this going nowhere... and that might make sense since my unit only has LEDs for Stereo and Timer, not SAP. So maybe that trace isn't supposed to exist... sorry, chatting with myself here = )

Welp, time to resolder the bugger back in, cleanly this time, and see what happens. If same issue persists, guess I'll need a new SBX module.

- Keith
SoCalRocker



Joined: 28 May 2008
Posts: 5

PostPosted: Fri May 30, 2008 12:23 am    Post subject: Reply with quote

Resoldered in the SBX module, same issue applies. = /

Unless anyone has any other suggestions, guess I'm in the market for a new module... I've just not run across a Google result where anyone's only lost 1 channel like this. All SBX issues I've run across are complete audio failure, noisy audio, or distortion. I really hate investing anymore $$$ into this. Time is not a problem, but if the SBX module doesn't fix the issue, I'll be out close to what you can get this set for on craigslist! : o

- Keith
kuhurdler



Joined: 28 Dec 2006
Posts: 2879
Location: Overland Park, KS

PostPosted: Fri May 30, 2008 5:32 am    Post subject: Reply with quote

I've come across the same problem before too when you find out it will be fairly costly to repair something.

I like to think of it as a hobby that I invest money in because I enjoy it. It helps me to make my bad decisions when money is concerned.
Jesse Mack



Joined: 22 May 2008
Posts: 600
Location: The Last Frontier

PostPosted: Fri May 30, 2008 11:29 am    Post subject: sbx1637-11 Reply with quote

There is a service bulliton about the sound distortion and the failure is the mm201 IC. The Sony part number for this IC is 874637120 and is officially No Longer Available. Its cost is $76.15
That being said, I am going to give little known parts source information. This information holds for most brands and parts. Go to the web site http://www3.sears.com and type in the model or part number and you will be supprised. They will sell to anyone and there markup is very small.

Hope this helps

Jesse
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