Hitachi 55hds69 No Picture

[mbates14]

Ran into this one. it is weird.

Powers on with sound, no picture. Missing Va, Vs and VCC voltage to sustain cards.

the supplies NEVER come up either.

Removed the plug from power supply to check boards for shorts, none found.

Powered on TV with Va/VS plug removed, still no supplies.

However, Q1512 on power supply module turns on hard +10v, effectively shorting out the Va/Vs through a 10 ohm resistor network, thus never giving the power supply any chance to come up.

Any ideas?

[mbates14]

Re: Hitachi 55hds69 No Picture

Im assuming this forms a crowbar circuit? Anyone familiar with this particular TV?

Also the gate is fed by a digital NPN style transistor which is fed off of a proprietary MCU thats on the power supply. MCU never toggles the transistor, so essentially the Va, Vs stays "crowbarred" the whole time.

I can tell its trying to start, becuase every light in the shop dims and power supply makes a loud CHIRP when turning on. but no Va, Vs voltage.

Of course not, because that MOSFET is turned hard-on. so its dumping Va/vs into a 10ohm load.

Wonder if its a bad power supply MCU or if its picking up some other issue and never letting the Va/Vs come up. As the MOSFET is not shorted. its just fine. but the minute you apply power and fire up the set, the gate gets a 10v DC. which locks the Va supply into crowbar.

[tonyklem]

Re: Hitachi 55hds69 No Picture

I'm having the same issue with my 55hds69. You seem to be fairly more knowledgeable than me when it comes to understanding the electronics. I did however notice that my Va and Vs voltages are nil. Does your blue LED (on the front of the TV) blink 8 times when you power it on? Let me know if you find a solution to this, thanks!

[cadiman]

Re: Hitachi 55hds69 No Picture

On this type I don`t think you can unplug either of the driver boards to check if power supply is going into protect mode. (If you do the tv won`t do anything). I have had luck unplugging the faulty buffers from the y drive and half the picture would come on (after repairing the power supply).

On these sets I have seen the buffers fail and take out the y drive board and the power supply, mostly on the 720p. The 1080s are better with less buffer chip failure but more power supply failure. I have worked on 2 of these. The 720s have been crash and burn and not worth the repair.

I don`t know much about your model but it looks very similar to the mosfet driven Hitachis I have worked on.

[jcaro]

Re: Hitachi 55hds69 No Picture

Hi, I'm having the problem with my 55HDS69 model TV. Power light turn blue but no picture. No Va, Vs, etc. All other voltages are there. Haven't tried removing one of the y buffer one at a time and powering up. Was scared I would blow a board.might give it a shot.

[jcaro]

Re: Hitachi 55hds69 No Picture

I replaced the lower y buffer and now I got top half of picture is ok but no bottom half picture. Suspect one of the lower abus-d boards. Any suggestions....

[queuebert]

Re: Hitachi 55hds69 No Picture

Perhaps the crowbar is locked because the PS never gets the Vsago & Vcego signals to turn on the Vs, Va & Vcc power rails from the Logic board, which which in turn first needs to receive "thumbs up" signals from the X & Y sustain boards.

I'm experiencing this same issue and my logic board isn't pulling high either Vsago or Vcego. Unfortunately, it's not easy to discern if this is a result of the logic board being faulty or it simply not receiving the "thumbs up" from the sustain boards. I've replaced the PS & YSUS boards and disconnected both SDR buffer boards to no avail.

Hitachi, like every other TV manufacturer, provides little in the way of schematics and troubleshooting data in the "service" manual.

[ajshoe]

Re: Hitachi 55hds69 No Picture

did u get this set fixed by replacing lower sdr board ? have same set with similiar issue - half screen. Has anybody compiled a diagnostic table for flashing leds and front of set and leds on digital board ??

[Shane711]

Re: Hitachi 55hds69 No Picture

I have this TV ( Hitachi 55hds69 ) and I have no picture.

I have had it for some time and have not been able to fix it. I have determined that my Y-SUS board is bad but I do not want to buy a used Y-SUS board that is only going to go bad again. So what I want to do is repair the Y-SUS board. So I need some help.

Let me first explain that I have tested just about every possible part on the Y-SUS board and it seems that there is a bad IC only because I can not detect any bad parts. My knowledge for testing ICs can use some improvement. I will attempt to look up each IC for info on testing.

The TV turns on and stays on with no trouble as long as I do not have an input source. As soon as I turn on an input source such as a DVD player then the picture goes out as well as my VS and VA.

I bought a cheap Y-SUS of eBay but with that board the TV did not work at all so now I have 2 non working Y-SUS boards.

Then I discovered I could test the scan driver boards by removing one at a time so I did that. Removed the lower board and the TV worked perfect and stayed on except I was missing the bottom half of the screen. So then I put that back and removed the upper board and again the TV works perfect except I have no top part of the screen. Puzzling.

It seems that when the TV is demanding the power it turns off, what could be causing this?

I tested every transistor and diode on the Y-SUS board. I removed every cap and tested them. Nothing bad found.

Whatever is causing the problem seems to get worse with time.

I took some pictures, if there is any IC you need a better PIC of I will upload it.

[Shane711]

Re: Hitachi 55hds69 No Picture

I also noticed that my VA and VS were too low so I tried adjusting them to the proper voltage. This did not make a difference either. Video stayed on for 20 seconds and video, VS, & VA dropped. Still have audio.

[ztimster]

Re: Hitachi 55hds69 No Picture

My Hitachi 55HDS69 stopped showing a picture after it was shipped to CA. It powers up and the on-screen menus work (they show up on the screen) but there is no image. Even when I set it to AIR there is no static. My computer identifies it so there is some communication through the HDMI cable, but no image.
Any idea what the culprit is??

Thanks!

[nomoresonys]

Re: Hitachi 55hds69 No Picture

Test connector from mainboard to powerboard on powerboard side with all boards hooked up, test with tv plugged in but off then hit power, report both conditions here, give pin number, pin description/name and condition both off and when you hit power on. So we can see all the voltages and what they are doing. Try to do test just as instructed, example in second link below if needed.

[nomoresonys]

Re: Hitachi 55hds69 No Picture

Inspect the screen carefully, it may have broke en route.

[R_J]

Re: Hitachi 55hds69 No Picture

It powers up and the on-screen menus work (they show up on the screen)

so it won't be a panel problem. Something came loose during transprortation, open it and have a look. or contact the shipper and report it damaged.

[nomoresonys]

Re: Hitachi 55hds69 No Picture

I've seen tvs with cracked screens that worked fine with crack showing on screen and seen them that didn't work at all, something may have come loose, many possibilities.

[nomoresonys]

Re: Hitachi 55hds69 No Picture

Example: https://www.badcaps.net/forum/showth...d+screen+works

[diif]

Re: Hitachi 55hds69 No Picture

I've seen tvs with cracked screens that worked fine with crack showing on screen and seen them that didn't work at all, something may have come loose, many possibilities.

You haven't seen a cracked plasma that works.

I suspect as R_J something has come loose.

[nomoresonys]

Re: Hitachi 55hds69 No Picture

Nobody said it was a plasma btw difboy.

[diif]

Re: Hitachi 55hds69 No Picture

Nobody said it was a plasma btw difboy.

The model number gives it away, it's mentioned several times in this thread.

[nomoresonys]

Re: Hitachi 55hds69 No Picture

It is a plasma difboy, IT IS NOT mentioned several times in post 11 which came 4 years after the rest of the thread, that it is a plasma. ANY other problems this morning??? We'll take it private so we don't shit up the thread. You want to discuss spelling, punctuation or anal retentiveness, just let me know.