Mits 46805 - Replaced IC's now picture is dim!

[NickB]

Having a problem with a Mitsubishi wt-46805 - I'm trying to fix my father's TV that developed convergence issues. I replaced the STK392-040 IC's with new ones from Acme and it fixed the convergence issue, however now the picture is really dim.

The picture seems to be dimmer on the right side of the screen, but it's like looking at a 20 year old tube set, just unwatchable. If I activate the "iris" feature the picture goes completely black.

I ohm'd out the resistors leading from the IC's and they are all within spec. Is it possible that I've got bad IC's? Can this cause a dim picture? I'd appreciate any suggestions on what else I should be looking for?

Thanks in advance.

[lcaillo]

No, the convergence output ICs have no effect on brightness. Did you by chance try to adjust focus? If you messed with the screen controls instead you may have affected the brightness. Other than that I would be looking for a loose connector or one that you did not reconnect. If the problem did not exist prior to the convergence repair it is most likely something that you did in the process.

[NickB]

Thanks for the quick reply. I didn't touch the focus or VR's, but we did move the TV into my fathers new place so maybe something got jostled during the move. I also I took the middle board out to do the repair so I'll go back and double check all of the connections and then post back.

BTW, thanks for your excellent DIY on the convergence issue. I was also able to fix my parents Panny PT53 (it was much easier to work on than the Mits)

[NickB]

I went over the whole set again, re-seating all the connectors and making sure they were securely fastened, but nothing changed (it's still pretty dark). I don't know if this means anything, but I did notice that when changing between channels the picture has what seems to be normal brightness for just a split second. I can see the intensity in the guns ramp up and then back down.

At this point I'm not sure what else to do. I'm thinking something may have happened to it during the move to his new place and will probably advise him to find a new set.

[lcaillo]

You need to examine the boards carefully for a coolant leak. Even a drop or two can create problems. Other than that, some troubleshooting and signal tracing will likely be needed.