Toshiba 32ZD98B CRT - picture issues...

[tmcw]

Toshiba 32" CRT
Model 32ZD98B
Chassis C9SS

Having a problem with the picture on this TV recently. Initially, after switch on, the TV would have the issue for a while, maybe 10 minutes, then suddenly would snap back to a perfect picture, but now, as soon as the TV is switched on, the picture has the issue.

Hard to describe. Like a severely grainy picture, or if you had scanlines, in a vertical orientation mainly, but also some horizontal exhibition too, but not fixed, the grainy lines move about randomly. The picture is split into about 6 "bands" it seems, you may be able to make them out in the first picture, the dark one (IMG_0338.JPG) - you may be able to see the leftmost 3 "bands". I've included another photo to show the issue.

The menu overlays, when invoked, don't suffer the same issue as the picture, they're clean and solid.

Tried all scarts, and the issue is the same on them all. Source is fine too, tested on another TV.

Any ideas where I should begin looking?

[Wizard]

Re: Toshiba 32ZD98B CRT - picture issues...

Replace the mainboard but check the capacitors on power supply to be sure first.

Cheers, Wizard

[tmcw]

Re: Toshiba 32ZD98B CRT - picture issues...

Cheers,

Not sure where I'd source a mainboard, or whether it would be worth doing/replacing on a 10+ y.o. TV.

I'll check the caps at the power supply before condemning it.

Was hoping that someone might have an idea why the issue was exhibiting itself, maybe narrow it down to a particular type of board, but I guess on a TV of this age, it could be anywhere.

[larrymoencurly]

Re: Toshiba 32ZD98B CRT - picture issues...

Does your library subscribe to Sams Photofacts online (www.samswebsite.com), where you can get many schematics free? I tried to look up the model but got only a projection TV because the index is mixed up. I think the chassis # is C9SS (projection TV is C8SS).

Otherwise, sci.electronics.repair?

[larrymoencurly]

Re: Toshiba 32ZD98B CRT - picture issues...

I think the manual here may be for a model very similar to yours, only it's PAL instead of NTSC. At least it's for the same C9SS chassis:

http://www.eserviceinfo.com/download.php?fileid=39194

You have to download all 9 parts (0-8), about 30MB total.

[PlainBill]

Re: Toshiba 32ZD98B CRT - picture issues...

It appears the complete manual is here also.

PlainBill

[Krankshaft]

Re: Toshiba 32ZD98B CRT - picture issues...

If the A/V inputs show the same faulty picture as the tuner it can be ruled out.

Since the OSD display displays fine the color drivers can be ruled out.

The issue probably lies around the Chroma/Deflection processing IC.

First thing to do after opening the set is to look for bulged caps especially in the PSU and processing IC areas you'd be surprised how many weird things they can do to a circuit.

Next check for bad solder joints with a magnifier since originally it was intermittent. If you have no luck by eye try poking the board with the TV running with something insulated like a long wooden dowel watch the screen for changes. Or try blasting the area with freeze spray it may cause the joint to act up and localize the area to look.

If it's not a solder joint or a cap issue then I'd be searching for an IC fault.

If your fault isn't a solder joint or cap issue it will take a bit more skill than a common CRT fault to troubleshoot.

[tmwalsh]

Re: Toshiba 32ZD98B CRT - picture issues...

If it were mine, I'd be looking for bad connections. Either solder joints or ribbon cables that are pressed into connectors.
tom

[mbates14]

Re: Toshiba 32ZD98B CRT - picture issues...

If its an HD toshiba? it probably has a hyper module, whos job is to upscan and reformat any picture information to the correct resolution that the CRT displays.

most if not all the SMD electrolytics are toast.

[tmcw]

Re: Toshiba 32ZD98B CRT - picture issues...

Thanks for the replies.

I've only had a chance to look at the TV today, and it seems like it's a bad connection. I've attached a photo, and the biggest riser card inside the metal shielding right in the centre of the photo is the one that was causing the issue (highlighted in a thin red line). From the few markings I could see inside the shielding and from looking through the schematics, I believe it's the DFS board (I could see QX01 and QX11 markings inside).

I poked a few areas inside with a wooden spoon, and when I moved this one slightly, the issue would come and go. I pulled it out a bit, and pushed it down, and it seems harder to cause the issue when I move the card slightly from side to side.

Looking underneath the card, it seems like it's attached to the mainboard with blue plastic connectors, but the shielding looks like it might be going through the mainboard, and maybe bent over or soldered to hold it down. I didn't try to lift it out fully.

I think if it happens again, I'll need to pull out the boards, and try to fix the problem more permanently. A quick google sees the issue coming up a few times with DFS boards, also with older Toshiba CRTs. Some of the fixes look like removing the DFS board, and resoldering some connections. We'll see how I get on.

Thanks again for the replies, helpful pointers and links. Much appreciated.

[tmcw]

Re: Toshiba 32ZD98B CRT - picture issues...

Ok, the TV didn't last very long before exhibiting the issue again. I've attached a few pictures.

The first 2 (Picture_G and Picture_B) show when the picture is good and bad. The problem is with the vertical graininess (there are some curved lines on both photos, but that's due to the camera).

I've also included a few pictures of the top-side of the boards, with the board that causes the problems usually towards the centre - it's the large square shaped one, with the top-forward (towards the tube) corner cut off it.

When I move the board either towards the power side of the TV, or even in the other direction, the issue comes and goes.

I've also included a picture of the underside of the board.

There are blue interconnection connectors between the power side of the chassis and the side where this problem board is, but they seem to be sound. Any flexing that results from moving the problem board shouldn't cause a problem on the power side with these connections. Also, if I move any of the other vertical boards, the same degree of flexing occurs, but the picture doesn't change from good to bad.

I also had the problem board off the mainboard. Four solder points removed it where the cage goes through the mainboard. It's connected to the mainboard through a connection not unlike an IDE connection. On the underside of the mainboard, I reflowed the solder that attaches the connector to the mainboard. I also tested the problem board for continuity between it's connector pins and the solder points on it's board - no problems detected.

I didn't take the problem board out of it's cage. There are a few heavy-duty solder points holding the board to the cage, and they all look sound. It's unlikely that moving the problem board causes movement inside here that would be causing the issue to come and go, is it?

Anything else I can try or test, or something I may have overlooked, or need to go back and check?