Toshiba 42H81 convergence problem

I forgot to mention that the blue is slightly out of focus and the focus control works, but it won't adjust to a sharp focus like the red and green.

There's no soft way to say it but, the DCU is screwed. The same exact thing happened to me a couple of months ago on the 50" flavor of that series. I had just done the entire convergence alignment and did a minor tweak in the service menu. The manual states when done, to exit service mode power off then back on. Did that and, mine looked worse than yours and there was nothing I could do but order the whole DCU for

104.00 from Andrews. If you don't have the manual, I can fire it off to you or at the least, the part number for it. Cheaper, I know to order the eeprom for that circuit but, if you're not Toshiba ASC all you'll get is a blank one. You'll still have to be ASC to have them program it. Also, make sure you order the circuit for that exact model. Mine just took a minor touchup and it was done. Lemme know if you need anything on that set.

Santy

You are probably right. I forgot to mention that I did a self diagnostic test with these results

SET ID : FF instead of SET ID : 01 EEP VER : FF instead of EEP VER : 02

I have the service manual and schematics already. But thanks for the offer.

Sorry, fogot the blue tube issue. I think you have two problems you're fighting and, a bad blue tube wouldn't be out of line to suggest. You could swap the screen/focus leads on the block with another tube to see but, if it adjusts like you say, my money's on the tube. Make sure you throw that possiblity out to the customer before investing big money on parts. Good luck.

Santy

I'll have to ask him if the picture was good before the convergence went bad.

This model seems familliar. Is this the one with the STK's on the small signal board, left side facing in from the rear? If so, look underneath the heatsinks and see if there are 2 surface mount IC's there. I've seen the logic ic's fail and cause this condition, if it is the chassis I'm thinking about. I could be wrong though.

Before 100% giving up on the blue CRT try the optical focus first :-) they have been known to defocus blue to help with the appearance of good color balance if the blue emission is a bit weak :-)

Jammy

I just had a look at the bottom of the board and there aren't any surface mount IC's on the bottom, just a few surface mount transistors. On the component side of the board there are 3 SMIC's

74HC14a,74HC123A and JLC1562B.

JLC1562B is the one I had to replace. You may still have a bad DAC though.

Jammy

I forgot to mention that there are some jumpers for the power supplies to the STK's near the heatsinks, and also some ground jumpers, I found on one of the sets bad solder on the ground connections, the joints looked good to the naked eye, but were noticeably bad under a magnifier. The faulty ground also damaged the JLC1562B.

Jammy

There is no way all the STKs failed at once. Ask the customer how long the set was running when this happened. If it was a very short time you might just need caps in the DCM (DCU). Problem is the data are scrambled now. In other words the reset routine didn't work right.

I wouldn't be afraid to try a blank EPROM in it before ordering the DCM. Thing is, you better be good at convergence.

We got one of these sitting at the shop, and the crosshatch pattern is like art, it really is. It came in with dead STKs but after replacing them we know the DCM drove them to death.

Anyway, a new DCM will require full alignment so an EPROM might be the way to go. Actually if you could just find a way to erase the EPROM in there now you might be alright.

If you can adjust any of the convergence, see if it actually adjusts the point where the cursor is, if not, screw it, get a DCM. If it adjusts the wrong place on the screen the processor is probably screwed, and having a major change when you change the EPROM doesn't indicate anything else.

Actually I succeeded once in aligning one that adjusted the wrong points on the screen and it never came back.

Let's put it this way, the DACs are seperate so all of them did not fail at the same time, the main processor(s) and the EPROM are what are common to all colors.

If, and it's a big if, you can align it, just check all the lytics and realign it. Problem is you might not be able to align it. If you can at that point it'll probably nevrer happen again.

Actually $107 isn't all that bad, if it's high definition, wait until the scan convertor (hyper module) goes !

Don't worry about the blue focus, for one it doesn't have to focused all that tight, and in some sets needs to be defocused to achieve color temperature. Of course the optical focus is set dead nuts, but there is an offset for the electrical focus. Going slowly through the range of the electrical focus, the blue should darken a bit. This is perfect focus and that is when you do the optical focus. Then you again offset the electrical focus. This only applies to blue on tri-CRT projection TVs.

JURB

I just checked for bad connections around the STK'S and allwere good Thanks Ray J

The customer said that he was watching a movie on his vcr and then was going to watch TV. When he was switching from antenna 1 to antenna 2 he hit the power button by mistake then immediately hit the power again to turn it back on. So I would guess that it was on for at least an hour.

I think I'll try a new EEPROM and see what happens. If a new one makes a difference then problem solved, if not I'll put the old one back in.

With the self diagnostic check saying the SET ID is FF instead of 01 and the EEP VERSION as FF instead of 02, I am leaning towards a bad EEPROM Thanks Ray J

Seeing what can happen first hand, if you install a blank eeprom in the DCU, make sure you have a fresh set of STK's and two 5 amp picos on hand. Good luck.