Sony Bravia KDL-46S4100 -- dead set condition

[gpenn01]

Hi all....

I have a Sony Bravia KDL-46S4100 bought new about 5 years ago. A few months back the daughter was watching the tv and it just shut off on its own.

I have finally found some time to take a look at it and did some online searches to get me started... thus finding this forum. This is where I am at so far:

- from this forum, I found and I am referencing the Sony training manual for this model tv.
- tv does not power up at all.
- verified 110V incoming to the G board (CN1)... ok.
- verified main fuse F1... ok.
- checked for 3.3V STBY on the G board (CN302 pin 3)... getting 0V.
- per the training manual, the next step is to replace the G board.

As such, I would ask for advice on my next step.... is there any thing else I can troubleshoot on the G board.... or.... just replace the G board?

I have searched online for the board and have only found a few on ebay for ~$30-$80 USD.

Thanks much...
Garth...

[R_J]

Re: Sony Bravia KDL-46S4100 -- dead set condition

Here is a link to the service manual
Do you have B+ on C801 C802 ? If you do, check for B++ on R614 that supplies the standby circuit on page 48.
B+ should be around 160V B++ will be slightly less maybe around 100 - 120v?
Check Q900 for short and check R937 should be 1ohm

[nuala]

Re: Sony Bravia KDL-46S4100 -- dead set condition

I would disconnect the t-con board first as it could have shorted caps and loading down the g board. See if the backlight comes on.

[gpenn01]

Re: Sony Bravia KDL-46S4100 -- dead set condition

Hi R_J and nuala....

Thanks for the manual and the items to check.... based on that, here is what I have found:

- disconnected the tcon board (by disconnecting the lvds cable).... no backlight... no obvious change in anything that I could see. Reconnected the tcon board.
- Checked B+ voltage on C801/C802..... 60V.
- Checked B++ voltage on R614.... 60V.
- Found data sheet online for Q900 then checked gate lead to source lead.... 120 ohms (I believe this should be infinite???). All other checks between the gate, drain, and source leads checked out as infinite.
- checked R937.... measured 1.2 ohms.

Thanks again...

[budm]

Re: Sony Bravia KDL-46S4100 -- dead set condition

Hi R_J and nuala....

Thanks for the manual and the items to check.... based on that, here is what I have found:

- disconnected the tcon board (by disconnecting the lvds cable).... no backlight... no obvious change in anything that I could see. Reconnected the tcon board.
- Checked B+ voltage on C801/C802..... 60V.
- Checked B++ voltage on R614.... 60V.
- Found data sheet online for Q900 then checked gate lead to source lead.... 120 ohms (I believe this should be infinite???). All other checks between the gate, drain, and source leads checked out as infinite.
- checked R937.... measured 1.2 ohms.

Thanks again...

OK, you are checking the DC voltage on the primary side of the board, you have to use the negative leg of the main filter cap as the ground ref point for your meter, not the chassis. So you need to take those voltage readings again.
When you make voltage measurement in the secondary side you can use the chassis ground as the ground ref for the meter.

[budm]

Re: Sony Bravia KDL-46S4100 -- dead set condition

BTW, how about good clear pictures of the back side of the TV and the power supply board.

[gpenn01]

Re: Sony Bravia KDL-46S4100 -- dead set condition

Hi Bud... thanks for the info... I have attached a few pictures as you have suggested. I am a bit uncertain as to the main filter cap you refer to... could you point me in its direction.

Again.... thanks much....

[budm]

Re: Sony Bravia KDL-46S4100 -- dead set condition

The two big brown caps, you must be real careful due to working in the primary side of the circuit.

[mmartell]

Re: Sony Bravia KDL-46S4100 -- dead set condition

budm means DON'T SLIP! with the probes !!

[truep]

Re: Sony Bravia KDL-46S4100 -- dead set condition

And DON'T touch the heat sinks!

[budm]

Re: Sony Bravia KDL-46S4100 -- dead set condition

And DON'T touch the heat sinks!

Yeah, that too. I would at least plug the unit into GFI Outlets. You can test the power supply board by itself without having it connected to other boards since we're only looking to see if at least the standby power supply is working or not.

[gpenn01]

Re: Sony Bravia KDL-46S4100 -- dead set condition

Thanks to all for the added advice....

I re-checked the voltages using the negative leg of the main filter caps as the ground reference....

Both B+ and B++ came up as 160V.

[gpenn01]

Re: Sony Bravia KDL-46S4100 -- dead set condition

I must have been half-a-sleep when I wrote that last post.... a H.U.A. moment.... because I should have stated that B++ was 0V.....

I double checked the board and I am measuring voltages as follows:
B+ = 167V
B++ = 0V

Note: H.U.A. = Head Up A#%

[gpenn01]

Re: Sony Bravia KDL-46S4100 -- dead set condition

Update...

Replaced the G board.... unable to find this specific board (# DPS-275MP-1A) at ShopJimmy or any other places online... found and ordered a used one from Ebay.... installed it tonight and TV is now working....