Mits HD1080 Conv. IC's Swap but no power

Mitsubishi HD1080 55" Rear Projection TV, Model WS55809, exhibited convergence problems,
whereby Red, Green & Blue CRT's lost alignment with corresponding images and concaved picture appeared on screen.
Digested earlier streams posted by Icallio, which matched condition,
purchased two new STK392-570 IC's, ($7.99/ea.)
removed Convergence Generator Board and replaced IC chips.
Tested solder joints with corresponding circuit traces and confirmed continuity.
Powered TV and was ecstatic when picture was restored.
Viewed program for 2 minutes then TV shut down independently.
Set restarts using either remote or Power button on front panel,
Green "Timer" LED lights, relay on rear of convergence board can be heard closing,
but system shuts down within 3-4 seconds as relay disengages.
Neither image nor sound have been detected since.
All visible fuses are intact.
Did note that one of new IC's was warmer than counterpart but
reattachment of heat sink was only 3/4 completed until certain of operation.
Still haven't acquired codes by depressing input and menu buttons simultaneously
for 5 seconds, to count the sequences of flashes from the LED but fear system
won't remain on long enough to do so.
Very perplexed, especially since TV was working previously,
(although convergence was misaligned) then worked perfectly after replacing
the two new STK392-570 IC's, but only for 2 minute period.
De-energized system, pulled board for second inspection, found no abnormalities,
replaced but results the same.
Downloaded both operator's and technical manual from Service Manuals.com,
listing schematics and general info but no troubleshooting FAQ's.
Got any suggestions?

Dave A

[lcaillo]

Where did you buy the ICs? Did you check the output resistors?

Most failures of these repairs are due to either missing a bad resistor, missing a bad connection or damaging a trace, bridging solder joints, or using poor quality replacement parts. It is common to get bad parts from MANY vendors. All of the reputable vendors of this part have it priced at about twice what you paid. Wonder how they get the price that low?

[xmonger]

I had a very similar (first) experience to yours. I would triple check everything outlined by lcaillo and replace the ICs with parts from a reputable vendor. I received great service from Acme (1-800-575-9833) and can recommend them.

Jerry

P.S. see my thread for my experience with non-Sanyo ICs.

http://www.hometheatershack.com/forums/manufacturers-service-support/11991-convergence-repair-initial-success-then-failure.html

[lcaillo]

Acme is one of the best suppliers around. They are very helpful and go to great lengths to understand the sources for the parts that they buy and assure that they are getting OEM parts. When I need to know something about a part, I am either calling them or B&D.

Icaillo,
Purchased IC's from BlueStar Int'l Components and had them within 3 days.
Haven't checked resistors on Convergence Board yet but very certain of clean IC installation
and positive solder joints weren't bridged.
Will use my Radio Shack "Dial A Resistor" and Fluke meter to confirm individual resistor values.
I'd hate to replace those chips again but after reading experiences of those
who've used inferior parts, that could well be my problem.
Since this is my first Big Screen blow up, I didn't know where to look for OEM parts.
Local electronics repair facility doesn't do Mitsubishi.
Essentially entered IC number into browser and up popped BlueStar.
Don't know if they fall into Good / Bad catagory.
In the event rest of the components check out,
I'll give ACME a call and order up another set of chips.
Hope to find time this weekend and will post findings.
Meanwhile, many thanks to Icaillo and Jerry for such quick response to my inquiry.

Respectfully

Dave A

[lcaillo]

Pull the diagnostic code first. Once you know what kind of shutdown you have you will know better where to look for the problem. If I understand you properly you were running the chips without proper heat sinking. If this is the case you likely blew an IC, and perhaps a fuse.

Will try the codes, providing set stays on long enough.
Heat sink was affixed to board, IC's leaning against it but retainer bar wasn't in place.
Their temperature wasn't hot to the touch, merely warm but I'll certainly take your advice.
Thanks again for input.

Called ACME this afternoon to acquire P&A of replacement STK392-570 Convergence IC's ($16.49).
Explained system failure after installing lower priced ($7.99) versions from another vendor.
Was informed that lot codes located on chip's upper right corner should be 5 digits for OEM products
and Chinese knock-offs have four instead.
Still haven't pulled board to confirm but thought info might save others some grief.

Dave A

Pulled Convergence board tonight and confirmed 5 digit lot code on new IC chips.
Must therefore conclude part is OEM, based on prior information.
Tested all resistors and diodes on board but found them intact and within tolerence.
Compared readings between pin 1 and balance of remaining 17 on both IC's.
Values same throughout.
Must conclude IC's are still intact and swapping them out for new ones currently enroute
would be futile.
Running out of options.
Any input from the group?

Dave A

Update:
Meant to say values matched from pin to pin between IC's.
ie: Reading between pin 1 & 4 (for instance) on first IC matched that of second, etc.

Dave A