Is this 55" Hitachi a good buy? (lines on screen)

[tom66]

Re: Is this 55" Hitachi a good buy? (lines on screen)

Think about it another way. Thanks to Hitachi's cost cutting, you got a $3,000 TV (which would cost at least $500 now) for $80 plus parts.

At the time of this TV, Hitachi Media Enterainment was on its last legs. They were hemorrhaging money in the plasma business. So they were cutting costs wherever they could to compete with Samsung and LG who would make TVs last 2-4 years and somehow customers would still come back for more.

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

Sigh... I got the buffer today in the mail and got it installed no problem. Although it did not fix the odd/even lines it did fix that thick line that existed 3/4 down the screen. I was happy that at least it was not a waste of money, but then BANG! Something blew up (on y-sus board I think) and the picture went out completely.

My theory is that the y-sus was half way dead to begin with (only displaying even lines) and for some reason the other half just blew. This y-sus board looks like it has two indentical circuits, each going to a separate buffer board. I was planning on comparing these two circuits to find the bad component, but now that it is completely blown, I'm SOL. This board is expensive so I would love to fix it. Where would you look first? Going over it with a flashlight now to find what went bang.

[tom66]

Re: Is this 55" Hitachi a good buy? (lines on screen)

It might be an interlaced driver, and maybe the bad buffer damaged it somehow. You have a large number of FETs and IGBTs on the board; check them individually for short circuits across source and drain. Also, check local Craigslist for a TV like this which is the victim of a flying Wii controller, or being dropped -- great for getting parts.

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

Can I check them in circuit?

[tom66]

Re: Is this 55" Hitachi a good buy? (lines on screen)

That should be fine, you will likely find a block are shorted (sharing a heatsink for example), and then you need to remove them one by one until the short goes. Sometimes more than one goes short.

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

I checked every 3 pin component that was labeled "G S D" between S and D and I found no shorts. Could it short between other pins or is there another component that is likely to POP?

[tom66]

Re: Is this 55" Hitachi a good buy? (lines on screen)

Is there a fuse on the board?

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

I'm searching hard for a fuse, it's small if its here. There is no short between ground and vcc, va, or vs.

[tom66]

Re: Is this 55" Hitachi a good buy? (lines on screen)

If you plug it in, do you still get good Vsus, or does it collapse below 1V?

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

Could vsus be labeled something else? vs?

[tom66]

Re: Is this 55" Hitachi a good buy? (lines on screen)

Yeah, sometimes Vs or Vsa.

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

If I test vs on ysus board I get 3.8v. This voltage comes from the xsus board. Is it malfunctioning?

[tom66]

Re: Is this 55" Hitachi a good buy? (lines on screen)

Vs comes from the power supply, unless it is routed through there first. Test it with the Y-sus disconnected.

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

With the power to ysus unhooked vs falls to -0.4mv when I turn the tv on. Power board daisy chains to xsus then from there to ysus. I was sitting directly in front of the xsus when I heard the pop. It didn't sound like xsus but I could be wrong.

I don't 100% trust this meter, I just found it in a drawer. I will bring my nice one home again and test again. If this xsus board is bad too I'm going to cry.

[tom66]

Re: Is this 55" Hitachi a good buy? (lines on screen)

I would find it hard to believe the X-sus to be bad. It's completely separate from the Y-sus -- it's not even connected to it through the panel. There's no direct connection between the scan and sustain electrodes, just a gap where plasma forms.

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

in this TV Ysus and Xsus are connected directly through a harness. PSU goes to Xsus which goes to Ysus. I'm afraid its bad because with the Ysus unhooked, Vs was non existent on Xsus.

[tom66]

Re: Is this 55" Hitachi a good buy? (lines on screen)

I remember one Pioneer/NEC I had shut down with no Ysus making identification of shorts difficult. In fact once I plugged it in it flashed red/green continuously until I reset it.

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

But the TV runs with sound, but no VS.

[tom66]

Re: Is this 55" Hitachi a good buy? (lines on screen)

I dunno then, any Vs with Xsus and Ysus disconnected?

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

Vs is only labeled on xsus and ysus. Shouldn't vs be coming directly from the psu somewhere?

Hold on, I see the test point on the psu. Let me check...