TV Repair Questions? Ask a TV Technician
The screen remains dark when I power it up, even in a dark room. I am unable to see any menus, images or anything at all. I can hear a click and startup tones as if the the mainboard is waking up. I replaced the mainboard as an uneducated wild guess of my own - ok so I don't get bragging rights.
I am sitting in front of it if there are any test you may need...
Have meter, no problem Va = 122, Vs = 122
Not sure of the other locations of the low voltage and temp
The heat sinks to the right and left of the power board are two degrees above room tem at 67 F
When turning on the set I do notice a red led on the power button that blinks four times if it helps.
led just blinking four times. the set has been powered up for about 45 minutes, no change in temp
The heat sinks are not warming up on either of the Sustain boards.
I am not sure which is the logic board, but there are no led lights lit on any of the boards, as viewed from the back. I even turned the lights off in the room and looked and no leds lit.
The Logic Board is below:
It operates off of a 12 or 15 volt DC output from the power supply. It's possible that the supply voltage is missing, as the Logic board drives the Sustain boards.
The board in the picture you linked to is not in this set. I looked it over, but I can not find that one here. The white wires off of the power supply board go to a board marked BN96-01856A
See if this helps...
Va, Ve, Vs, Vset, Vscan are all 122 at this point. with the set on
Heat sinks on the power supply board are between room temp and 93F
Sinks on the Sustain boards are room temp
Vs = 122 (Which is the house voltage)
Chart found on power supply board attached
Ok so are we saying that it is the power supply board that needs to be replaced? And if so could you provide a link to order one?
After unplugging the Sustain boards Vs still reads 122 v
Ok, one last question
Can you provide a link where I can get this at a reasonable price?
Preferably someplace that takes PayPal for safetys sake.
First I want to say that board is going to be extremely rare, whether the site takers Paypal, or is a reasonable price is beyond my control. I can only tell you what it takes to repair the TV.
Below are the links I was able to locate the board from:
If you need further assistance let me know and please do not forget to rate my service accordingly.
Your advice was great, I have ordered the part and am waiting for it to arrive. I guess the ultimate test will be when I install it and see if the set works. Thank you!
I got the board and installed it, unfortunately its still not working. Umm, what now?
Ok, a couple of updates.
There is a logic board under the metal cradle for the main board. When the set is turned on it has two lights on a flashing green one on the left and a solid green one on the right.
The Vs (as measured on VDC between RTN post and Vs post) is 14.1volts with the set on.
Would this be easier for you on some sort of video conference so you can see what's going on? It is possible as I have a good connection and a camera on my laptop.
Though I cant seem to find a Vsus, just a Vs which measures 14.1
Just figured out that I forgot to plug a connector back into the mainboard. After plugging that back in the Vs now measures 13.9 VDC
Should I try to turn the VS-adj up ?
Ok After that I measured Vs at 14.2 VDC, not much difference there.
I can switch back to the old power board and re check that one?
Switched back to old power board and double checked all the connections. Vs is now 15.0 Vdc
I do have a different meter. The old one met its demise earlier today when I was working on an outboard boat motor and dropped it in the test tank. (I own marinas for a living) This one is new as I just picked it up today at the local WalMart. I did check it against a nine volt battery and it checks out ok. Possibly the old meter was bad to begin with.
This meter I have set to DCV and I am measuring with the negative (black) probe on the RTN post and the positive probe on the Vs post on the power supply board.
Ok, it already is on DCV, like what is in the picture in this link
I think that is the highest setting for DC
I don't have another meter. I did just check it against another power supply I have here and it measures 13.73 VDC on a "Switched 13.8v power Supply" from Radio Shack. The manual that came with the meter says it will go to 600v.
As a contrast test I measure outlet voltage at 123.7 ACV.
I know its not a high dollar meter like a Fluke or something but it should be fairly accurate.
I would check with the old meter but it got hit by the prop in the test tank. Not a chance it even works.
Is it possible we have two bad power boards?
Hi and welcome,Thank you for the question and your patience. Should you still need assistance for information purposes only... Initially, to my understanding, there are two (2) SMPS power supply boards on this model; main (something like a P/N BN96-03252A) and DC/DC (something like a P/N BN96-01856A).
Still, propose to carefully check the DC voltages [presence & consistency] (without adjusting any if the trimpots) and using the metal frame/chassis as common ground:
Please post back results / observations.
Hi Louie, thanks for your help!
Ok, so far none of the trimpots have been adjusted. The old AC to DC power board (the large one) is installed, and I do have another. Here are the measurements with the negative lead connected to the chassis (where to mainboard groundwire is connected)
Vs = 10.2 dcv
Va = 66.0 dcv
Vset = -1.3 dcv
Ve = .205 dcv
Vscan = -5.76 dcv
I am not sure of where to measure "low DC", "PS_ON", or "VS_ON".
But if you can explain I can follow directions.
Ok connector CN809 on main Power Supply board (the larger one)
1 - 13.4 vdc
2 - 13.3 vdc
3 - -1.0 vdc
4 - 65.0 vdc
5 - 64.9 vdc
6 - -2.5 vdc
7 - -2.5 vdc
8 - -2.6 vdc
9 - -2.8 vdc
10 - -2.9 vdc
11 - 14.89 vdc
12 - 5.24 vdc
Which connectors would you like me to test on the smaller DC to DC board?
I'm not sure where to test that. I can't seem to find that on the board. Where and how should I test PS_ON and VS_ON ?
PS_ON = 1.4 vdc (from cn804-1 pin 6)
VS_on = 3.25 vdc (from cn810 pin 9)
ok with all cables plugged in Vs = 13.1 vdc
With cn5010 unplugged Vs = 3.47 vdc
With all cables in place Vs = 14.1vdc
With CN4004 disconnected Vs = -0.2 vdc
I would be happy to but I can see a bad chip on the other board (which was the old one that was original to the TV) so I know its bad. It is the chip at u403 just below the large yellow transformer at the top middle of the board.
The board that is in the set currently was one I got from Tri-State Module and they said they tested it before shipping it out.
Is there a way to verify that it is good?
With all connected Vs = 14.0 vdc
Va = 64.9 vdc
with cn809 disconnected Vs = Steadily climbs in voltage about 1 volt per each 5 seconds - this seems weird??
With cn804-1 and cn803 disconnected and the pins shorted I measured
Vs= 0 vdc
Va = .401 vdc
Shorting pins 4 & 5 is supposed to kick start the power supply. It appears that it is unable to do so.Replacing the power supply would be the only option left both as an attempt of a fix and as an elimination test.
Ok,I will call Tri-State on Monday and have this board replaced. After the new one arrives and its installed I will let you know. Thanks!