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Toshiba 57H82 convergence ICs or other issue?

5469 Views 4 Replies 2 Participants Last post by  DaveCh
Greetings! I've read the wonderful "CRT based RPTV Convergence Repairs" sticky thread a couple of times and was hoping I could get a suggestion or tip on how best to proceed with my specific issue.

My 9 year old 57H82 recently had the green go way out of convergence. The symptom is that in the service mode convergence screen the green lines are very curved up at the bottom left (bowed up by several inches) and also curve up on the top right. The green lines up reasonably well at most other places (in particular in the center of the screen) and red and blue are fine everywhere.

When I run "Touch Focus" the lines for each colour move both horizontally and vertically (although the green lines are bowed as above, especially at the bottom left) and a "Touch Focus Error" is returned. If I manually try to adjust the convergence in service mode all the colours respond in both horizontal and vertical in most places; the exception is that the green doesn't seem to respond very well if I attempt to adjust points in the lower left of the screen where it's the worse.

From what I gather, the most likely problem is one of:
  1. The convergence output ICs. Some places on the web stop there and say all such problems means you should change out the ICs and check/replace related resistors.
  2. A blown/open/bad resistor or pico fuse near the convergence ICs.
  3. Bad/aged solder joints.
  4. The power supply to the convergence circuits.
  5. The convergence generator circuit.
  6. The green deflection yoke or green tube, etc.

I would have gone ahead and do the common convergence repair indicated by problem #1 but in the sticky thread it says:
If all of the adjustments for R,G,& B, both horizontal and vertical have an effect, your problem is somewhere other than the output ICs.
Since I can adjust all those (except for at the problem area) does that mean that my ICs are probably not the (main) problem?

Am I correct that to test the resistors for #2 I need to remove the ICs or unsolder a leg of each resistor?

My brother is great with a soldering gun and repairs audio amplifiers and the like regularly. He went over all the solder joints for me, he said a few looked suspicious, but nothing changed after touching them up.

After reading the sticky thread about how convergence works I figured it was safe to do a quick diagnostic test for (unlikely) #6. I swapped the green and red sub-deflection yoke connections on the signal board and verified that when powered up the green lines were back to straight and the red lines where bowed out. That tells me everything after that connection is probably good with green.

So my main question is should I go ahead and try replacing the convergence ICs and check the resistors while they're out? From what I read I think I should replace the existing STK392-110 with STK392-150 if I do this.

Or should I look at something else first. What? The power to the convergence circuit? The inputs to the ICs? I understand the last involves checking for specific waveforms, can this last be done (just basically at least) with a scope without knowing exactly what the waveforms should be? Did I miss anything major/likely in my list above?

Thank you ahead of time for any helpful input!
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You almost certainly have a bad IC. Not all of the adjustments work normally. Either the -110 or the -150 will work, but IMO there is no reason to get the latter in this set IF you are buying your parts from one of the recommended suppliers and are sure they are original first quality parts. Given the choice of the -150 from a seller I did not know vs -110 from one that I was confident in there would be no choice but to use the -110.

Resistors need to be tested with the chips out and the yokes disconnected. It is not usually necessary to delolder them at all, but that can vary with the circuit and your testing skills.

Resolder anything that is even remotely resembling a cracked joint. MANY people have been fooled by these, and moving the boards around can create problems with solder connections.
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Thank you for the quick reply and the suggestions regarding the -110 vs -150. I was worried that my symptoms didn't match failed ICs and that I'd be wasting my time. Thanks for reassuring me (although I get that I may still have other problems and there is no guarantees).

I'll go ahead and order the parts and let the forum know how the repair goes.

Thanks again for the wonderful "CRT based RPTV Convergence Repairs" thread!
Be sure to order your parts from a trusted supplier AND triple check for cracked solder joints. It is very common to get bad parts and to blow good ones by missing bad solder connections.
Success! :jiggy:

The delay was due to my ordering the parts from ACME in Florida. For reference, if you're in Canada you might want to find a closer place to order from (although as lcaillo says make sure it's a trusted supplier) or be patient and ignore the tracking info USPS gives you (my tracking number still just has a single entry saying the package was picked up). They (possibly Canada Post?) also left the package in a door I don't use and I didn't notice it for awhile.

Anyway... my brother did the soldering for me, he checked all the resistors and they were fine. Plugged the board back in and it worked great.

I went with the -150's since they were only a couple of bucks more and in another thread you had said you thought they were/might-be superior. Since I was ordering from one of the places you recommend I figured both the -110s and -150s would be genuine parts.

:thankyou: Thanks again for your advice here and your other wonderful posts on this site about convergence issues. You made me much more comfortable with ordering the parts and trying the repair rather than spending money I don't have for a local technician of unknown quality.
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