Another 42H83 conundrum.

[invader_star]

Re: Another 42H83 conundrum.

Found two problematic fuses, (F852 2A, and F850 5A) that seem to be bad.
I found them on B&D. Will replace.

Just to be sure, would these two fuses cause the picture to go out? Is this the reason why I lost picture?

[Wizard]

Re: Another 42H83 conundrum.

Scroll back.

Reason this was let go too long then things blew out was a small jumper somewhere near the edge of that small signal board (where STK 392 are) had tiny bad joint on that jumper wire. One I had was easy to miss but I had to look real close and it was. That how hard to spot. My best suggestion is solder all jumpers around that STK for about 2 inches either side of it right to the edge.

Good searching on the fuses.

Cheers, Wizard

[invader_star]

Re: Another 42H83 conundrum.

Back from the dead; after ordering the two ICs and several pico fuses we got the rig soldered up, and put back together. We double checked several jumper lines to make sure continuity is running through.

Alas, the first boot is a success! Turns on just fine.

However, the Blue seems to be out of whack. Green and Red are just fine. Working perfectly. But the Blue is wavy and sporatic. After having the unit on for a few minutes, a touch focus was attempted. It failed. I've heard of having to try and getting the tubes re-synced after this kind of conversion, but I'm still looking into how to fix the issue.

Any thoughts? I'll try and take a picture here soon.

[invader_star]

Re: Another 42H83 conundrum.

http://www.youtube.com/watch?v=Qtptzn0Uqvc

Framerate is kind of bad, but skip to half way through.

[Wizard]

Re: Another 42H83 conundrum.

Don't check the jumpers, Solder them just in case!

Replace both STK ICs. Jittering of convergence is sign of STK ICs beginning to fail and bad solder joints will kill the IC also if left there too long. That means pull the small signal main board out again and replace both ICs and go over the board again with soldering iron and solder including few jumpers I mentioned, the main reason for the fuses to blow.

Cheers, Wizard

[Krankshaft]

Re: Another 42H83 conundrum.

Make sure that you get the STKs from a legitimate source so you don't get rejects.

Here is a good place:

http://www.encompassparts.com

Here is a primer on STK replacement:

http://www.hometheatershack.com/foru...e-repairs.html

Be sure to upgrade your current ICs using the table in that thread.

Encompass sells them in a pack of two which is cheaper than one.

You will also need to replace at least 1 resistor that is probably blown. It will be one of the large resistors standing off not too far from the STK ICs.

[invader_star]

Re: Another 42H83 conundrum.

Soooo, what you're both saying is that the STKs we got from B&D, which was recommended by Wizard, were rejects? And already failing from when we threw them onto the board?

This is frustrating. :\

[Krankshaft]

Re: Another 42H83 conundrum.

Oh you replaced them?

No B&D is fine look for an open resistor.

They will probably be large and sky blue.

I am hoping bad joints didn't kill your new ICs right out of that gate.

It's a common fact about TV repair though if you don't do your homework first and really check the surrounding circuits supplying the component you're replacing. You can run the risk of frying the part.

[invader_star]

Re: Another 42H83 conundrum.

Yeahhh, true. We only knew of pico fuses potentially being an issue, and frankly that's all we looked for. We re-soldered several jumper wires, too surrounding the ICs.

I'm hoping so, too. It hasn't been on longer than a few minutes each boot, so hopefully everything is intact. I'll look for those resistors.

[Wizard]

Re: Another 42H83 conundrum.

Good. That happens. Still just go ahead and change ICs. Good luck!

Cheers, Wizard

[Toasty]

Re: Another 42H83 conundrum.

Wizard - He already did replace them.

Are you saying to replace them again??

Toast

[Wizard]

Re: Another 42H83 conundrum.

This unit will not power up with blown fuses by it's design (annoying) and had no idea if the STK is still good, whatever is sick or bad that it takes fuses out again. Lucky that and now we know that STK ICs are bad due to jittering convergence. That what I meant by replace both ICs.

it is not easier on this toshiba bec of design it has, on other units when fuse blow, tv kept going with non-functional STK amp convergence ICs (no power due to fuses). Or easily unplugged to test if the PSU will not run into shorted load (some makes did not have fuses FYI).

Cheers, Wizard

[Toasty]

Re: Another 42H83 conundrum.

No. I guess I wasn't clear. He said:

Soooo, what you're both saying is that the STKs we got from B&D, which was recommended by Wizard, were rejects? And already failing from when we threw them onto the board?

This is frustrating. :\

My question was/is - Does he now have to replace them again?

Toast

[Wizard]

Re: Another 42H83 conundrum.

Oooh. Didn't realize ICs were replaced.

Sounds like might had missed solder joints and check the resistors, these grey or red or like that is stood off the board. When I do this type of job in toshiba, we always resolder lot of joints and measure these resistors and resolder them.

The convergence generator is in smaller upright box next to the convergence ampifier heatsinks. Resolder the pins and check inside so all is good.

Basically, Toshiba is notorious for solder joints and capacitors as we have mentioned.

Cheers, Wizard

[Krankshaft]

Re: Another 42H83 conundrum.

I would check the resistors first on my Toshiba when the amps went at least 1 resistor opened. I replaced all 6 resistors 3 per IC.

They were sky blue and standing off the board near the ICs.

The fluttering convergence I did experience when the ICs were about to bite the dust the blue drifted vertically then snapped back into convergence rinse and repeat.

Eventually the IC went and it remained out of convergence.

My originals were STK392-110 I replaced them with STK 394-160 a more reliable design plus they come in a Hitachi kit (pack of 2) for about 30 bucks.

However if you replaced them lets focus on bad solder joints or missed components like resistors as others said.

[invader_star]

Re: Another 42H83 conundrum.

Hello all, apologies for the extreme absence. I had lost most hope for awhile and until recently have been tired of staring at the TV in my living room.

I followed Krankshaft's advice and checked all of the sky blue resistors around the ICs. There were only four or five that I saw and tested; pulled them out of the circuit, tested, and replaced. Only one resistor seemed to be a little off, (1.1ohms, instead of 0.82ohms) but the percentage of error seemed acceptable, so I put it back in. Resoldered every resistor, naturally, and cleaned it with some isopropyl. Fired it back up and still have the retarded blue color. Green and Red are absolutely perfect, but the blue is still freaking out. I can touch focus, and it says completed, but you know, blue is all lame.

I don't know what to do at this point. Replacing the ICs again is a little out of the question from a financial stand point, so. Looking for ideas. I appreciate the help you've already given me. You guys are great.

[invader_star]

Re: Another 42H83 conundrum.

*I would have edited my first post but it's been longer than 10 minutes.

I just checked the convergence generator, and to my eye all of the joints seem to be adequate. Nothing is blatantly bad, or looks bad. I can take a picture or something for a little more in depth scrutinizing.

[Wizard]

Re: Another 42H83 conundrum.

Change the 1.1Ohm. Has to be .82 ohm. These resistor is 5% tolerance, it affects the quality of convergence.

And you still have to resolder the wire jumpers on the small signal mainboard. Or the fuses and convergence blown again. That one jumper I found was at first glance was good, but it is truly bad solder, micro fracture right at the wire/solder junction! It was discussed frequently on other forums about this.

Cheers, Wizard

[invader_star]

Re: Another 42H83 conundrum.

Okay. I'll go ahead and replace that one.
Just for clarification the 'small signal board' is the one board that holds the two IC chips, and the inputs go into?

[Wizard]

Re: Another 42H83 conundrum.

yes!

Cheers, Wizard