Toshiba TP48D51 proj TV dumpster find

[SteveNielsen]

Looks like I have bit onto a big one here. Someone set this out with manual and remote by the dumpster and I couldn't resist.

It does power up but looks like the mirror and/or lenses got knocked out of whack. Judging by a pretty good ding on the base of the cabinet it probably had a rough trip down the stairs. I've attached some pics. The thing is pretty huge. I'm thankful they made it with casters. I haven't looked inside at all yet.

I don't have experience with projection TVs, I've only seen one or two opened up.

[stj]

Re: Toshiba TP48D51 proj TV dumpster find

what technology is it,
3crt?
dlp+lamp?

[tom66]

Re: Toshiba TP48D51 proj TV dumpster find

Looks like a 3CRT with the common STK conversion issue.

[stj]

Re: Toshiba TP48D51 proj TV dumpster find

ah - looking at the pics, it's 3crt's

check the liquid-cooled lenses are all still filled with liquid and fitted to the tubes properly.
and check that they are clear - for some eason the liquid in the blue ones goes foggy sometimes!

[R_J]

Re: Toshiba TP48D51 proj TV dumpster find

You have no convergence correction, I suspect shorted stk-*** ic's and open pico fuses on the deflection board

[SteveNielsen]

Re: Toshiba TP48D51 proj TV dumpster find

Thanks for the information. I'm doing a little reading about the STK covergence issue. Sure looks that way so far.

Here's a couple more pics and a couple of questions.

What is that horizontal thing midway up the back with what appear to be two pry holes at the bottom ends? Mirror or something slide in there?

Is the board shown in 2nd pic the convergence board?

[R_J]

Re: Toshiba TP48D51 proj TV dumpster find

Yes thats the convergence board, the mirror is located in that top part attached to the back. I have no idea why someone was prying on it. to gain access to the mirror you need to remove the front screen assembly, If I remember correctly. I don't have this manual anymore.

there are 2 pico fuse I believe on the convergence board F701 and F702 2amp. check them and see if they are open.

[SteveNielsen]

Re: Toshiba TP48D51 proj TV dumpster find

F701 is good, F702 is open. Checked out of ckt.

The convergence chips are STK392-020s. The board is a tad dusty but looks ok, nothing obvious pops out but I'll take a couple of pics. That helps me to get a zoomed in view for myself with these worn visual sensors in my head

[stj]

Re: Toshiba TP48D51 proj TV dumpster find

check what i said,
if it got banged around when it was dumped and a lense comes loose or drains it's coolant you will burn the phosphor off the front of the tube.

i had a load of ex-rental projectors once and it was a nasty problem!

[SteveNielsen]

Re: Toshiba TP48D51 proj TV dumpster find

Thanks stj, took me a bit to get to doing that. I can't work sitting on the floor for very long anymore

I got an inner cover off and visually checked what I could of the lenses and see nothing out of the ordinary. They appear properly mounted, intact and no sign of any leaking liquid.

I read at another forum site according to a quoted (not linked) Toshiba tech bulletin says if F702 is open then Q701 (one of the 2 STK chips) is blown (and vice versa, if F701 opens then Q702 is blown), to check the resistors around that chip and mentioned a couple of solder joints to touch up. That was for a TP48D50. Close enough to a TP48D51 to apply? I'm not finding much else than people trying to sell me repair kits online

I just checked the resistors around both chips and they are all ok. What pins should I check on the chips for a short?

[tom66]

Re: Toshiba TP48D51 proj TV dumpster find

The fact that your distortion affects all three channels (six deflection channels) would, to me, suggest both ICs are bad. but I am not sure why both would go bad at once, it is odd.

[SteveNielsen]

Re: Toshiba TP48D51 proj TV dumpster find

I though of that too but each IC has 3 channels, so it is possible that one chip is assigned to the X axes of all three CRTs and the other to the Y axes of them.

I can't find a schematic or even a block diagram for this board yet so who knows how they spread that out?

[tom66]

Re: Toshiba TP48D51 proj TV dumpster find

Both X and Y appear bad, to me. Am I missing something? Only ever done one CRT RPTV.

[SteveNielsen]

Re: Toshiba TP48D51 proj TV dumpster find

You're one up on me then, I've only seen one taken apart before and by the time I saw it the jerk had it in pieces and lens fluid leaking everywhere and was busy throwing parts in the trash.

[stj]

Re: Toshiba TP48D51 proj TV dumpster find

it's also possible that the power going to the chips isnt stable.
is the distortion stable, or moving around when you view it?

[SteveNielsen]

Re: Toshiba TP48D51 proj TV dumpster find

It is stable.

[stj]

Re: Toshiba TP48D51 proj TV dumpster find

not the power then.

maybe - just as a test, swap the 2 ic's around.

[SteveNielsen]

Re: Toshiba TP48D51 proj TV dumpster find

I suppose I could, although that is doubling the board exposure to my desoldering/soldering skills or lack thereof.

Looking at the bottom of the board with a magnifying glass I do see some iffy-looking solder joints I should probably touch up and the tech bulletin mentioned some of that being a concern.

Can I use any generic 125v 2a fuse for the one that's open?

I did find a PDF of the chip specs if that might help but that 22-pin thing has got more vcc+'s and vcc-'s of various designations than Carter's got little liver pills. There is a separate vcc+ and vcc- for each channel as well as separate pre vcc+ and pre vcc- for each channel (whatever that is). I'd be nice to be able to test the chips for shorts first, but where to start?

Perhaps I should just order two of the ICs and replace them both anyway?

[stj]

Re: Toshiba TP48D51 proj TV dumpster find

fuses are prefixed "F" or "T" dont mix them up - the difference is important.

[SteveNielsen]

Re: Toshiba TP48D51 proj TV dumpster find

Ok, F is fast and T is timed (aka slow blow), correct? The fuses themselves have designation of 50C 2A but on the board are designated as F701 and F702 and in big block letters 2A 125V by both of them. Does that make em T's or F's? I'm guessing F's. I don't mean to seem like a total neophyte but there's a lot of tech stuff I've missed out on over the years of being stuck in network admin jobs and a lot that's been subject to personal memory leaks and I just want to make sure.