Sylvania 42" LC427SSX Strange HDMI Problem

[XtraTN]

Alright, so heres the odd problem I have with this model TV. If i hook the TV up with the antenna input it works fine as I turn it on. Everything works fine when it turns on without an HDMI cable plugged in. If I turn on the TV while an HDMI is plugged in, there would be no sound and all the HDMI inputs (ie. HDMI 1, 2, 3) would display the antenna input (with no sound in any). However if i unplug the HDMI cable, turn off the TV and turn it back on with only the ANT plugged and then I plug in the HDMI cable after it is on everything works perfectly. Switching between inputs are normal. It just once I turn on the TV while the HDMI cable is plugged in that I have this problem with no sound and messed up HDMI inputs.

Any ideas?

[tom66]

Re: Sylvania 42" LC427SSX Strange HDMI Problem

Firmware update? Sylvania isn't a company any more, they are just a name, manufactured by Funai Electronics I think. It would not surprise me if they released a version with bad firmware. Is the probem new, or has it always existed?

[selldoor]

Re: Sylvania 42" LC427SSX Strange HDMI Problem

Have you tried a new/different hdmi cable

[XtraTN]

Re: Sylvania 42" LC427SSX Strange HDMI Problem

Alright I think I have solved the problem with this one. I assumed the issue with either within the HDMI or Main board. I measured voltages of when the TV works fine, and voltages of when it doesnt. Around the speaker inputs on the mainboard, I found a slight increase of from 2.56V to 2.62V as I tested it while working and non-working. I traced it to any near components and found a capacitor.

Its a smaller capacitor of 47 uf and 25V. I measured the positive terminal and it measured both 5.24V both working and non-working. The negative terminal however had the slight change from 2.56V to 2.62V. From my limited knowledge I wasn't sure if it was relevant or not but I couldn't find any voltage changes on the hdmi board. So I took a shot to confirm if it was really the capacitor. I took another capacitor on the mainboard with the same ratings (assuming it is still good) and switched the two and once i tested the TV again the problem has actually changed! So to my knowledge i'm pretty sure it is this little 47 uf 25V capacitor that is causing the problem. I switched the two capacitors back into there original places and the problem is back (making sure it wasn't just my soldering job =])

So now I just need to find a new capacitor for this. At least I'm kinda confident that this capacitor is the problem. I'm starting to see the benefits of having a capacitance and ESR meter and thinking i'm about invest in one. How common do smaller capacitors fail? I always thought the smaller ones tend to fail less (though most of the capacitors are of su'scon brand). Should I actually change all the capacitors on the board? Any thoughts would be great!

[XtraTN]

Re: Sylvania 42" LC427SSX Strange HDMI Problem

Actually just replaced the capacitor and the problem is still there. The problem is new, one day the sound just went out and i started getting this problem. =/ Well im stumped, as for the firmwire update, where and how would I upgrade it?

[tom66]

Re: Sylvania 42" LC427SSX Strange HDMI Problem

Firmware updates are often done over-the-air, but only higher tier manufacturers pay TV stations to transmit these updates. I would suggest checking any LDOs (regulators) around the HDMI area. Post some pictures of the boards.

[XtraTN]

Re: Sylvania 42" LC427SSX Strange HDMI Problem

So its not possible to download an update file for the TV? I find it odd that it because the TV actually has a USB port.

I took measurements on the hdmi board specifically on the back of the board where the LDO are located while the TV was on and sound not working.

How do you know if an LDO is bad? The measurements are on the given photo. First photo is of the hdmi board, second is the main board.

[tom66]

Re: Sylvania 42" LC427SSX Strange HDMI Problem

No luck on info about those regulators. Are all the numbers the same?

[XtraTN]

Re: Sylvania 42" LC427SSX Strange HDMI Problem

Yes all the numbers are the same. They read BD7820 94 26

[selldoor]

Re: Sylvania 42" LC427SSX Strange HDMI Problem

Is it one of these
http://elcodis.com/parts/5629732/BD7...html#datasheet

[XtraTN]

Re: Sylvania 42" LC427SSX Strange HDMI Problem

I'm not familar at reading these diagrams any help? thanks!

[XtraTN]

Re: Sylvania 42" LC427SSX Strange HDMI Problem

Well, I did a bit more probing on the hdmi board and found something very interesting. Heres a photo of the front of the HDMI board.

When I tried to measure voltages on the given pins (IC3101 and C3118) that i show on the second picture, the TV seems to turn off and as I remove my probe from the pins, the TV would turn back on and working perfectly with sound and everything. I checked the other pins of the same components but it was normal. At first I thought I short circuited it but I tried probing it again more carefully but still the same problem happened. Next I thought it was due to a cold solder joint so I applied a little pressure on top of the component itself but no change so I don't think thats the problem.

I'm not sure what it means, would it point to a bad smd capacitor or the other component (not sure what its called)?

[tom66]

Re: Sylvania 42" LC427SSX Strange HDMI Problem

Ceramic capacitors (the little brown things) are pressure sensitive. Pressing on them can induce a voltage which could cause the TV to do odd things.

[XtraTN]

Re: Sylvania 42" LC427SSX Strange HDMI Problem

what about the component above the ceramic capacitor? Even slighty touching and probing for a voltage measurement at the bottom left pin causes the TV to turn off as if my multimeter is preventing the TV from turning on.

[tom66]

Re: Sylvania 42" LC427SSX Strange HDMI Problem

what about the component above the ceramic capacitor? Even slighty touching and probing for a voltage measurement at the bottom left pin causes the TV to turn off as if my multimeter is preventing the TV from turning on.

What about applying pressure to the epoxy package? I have a TV here with a faulty LDO which will occasionally work if you apply pressure to it. I suspect it has a loose contact on the semiconductor die.

[tieny]

Re: Sylvania 42" LC427SSX Strange HDMI Problem

What do you mean by epoxy package?

[XtraTN]

Re: Sylvania 42" LC427SSX Strange HDMI Problem

I tried applying pressure to the component and area around it but theres no change or reaction. Well I found that the TV will turn off only when I have one of the probes grounded and the other touching the pin (as if to measure the voltage). If I touch the pin with just a probe while the other isn't grounded, there is no reaction.

[tom66]

Re: Sylvania 42" LC427SSX Strange HDMI Problem

I tried applying pressure to the component and area around it but theres no change or reaction. Well I found that the TV will turn off only when I have one of the probes grounded and the other touching the pin (as if to measure the voltage). If I touch the pin with just a probe while the other isn't grounded, there is no reaction.

I suspect it's just interference or loading by your meter, are you using a DMM or analog meter?

[XtraTN]

Re: Sylvania 42" LC427SSX Strange HDMI Problem

I'm using an digital multimeter

[tom66]

Re: Sylvania 42" LC427SSX Strange HDMI Problem

I'm using an digital multimeter

Strange, but I wouldn't consider it a fault.