Mits HD1080 Conv. IC's Swap but no power

3933 Views 27 Replies 2 Participants Last post by Dave A, Aug 24, 2008

G

Discussion Starter · Jul 14, 2008 (Edited)

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

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lcaillo

· #2 · Jul 15, 2008

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

· #3 · Jul 17, 2008

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/for...ence-repair-initial-success-then-failure.html

lcaillo

· #4 · Jul 17, 2008

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.

G

Discussion Starter · #5 · Jul 18, 2008

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

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lcaillo

· #6 · Jul 18, 2008

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.

G

Discussion Starter · #7 · Jul 18, 2008

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.

G

Discussion Starter · #8 · Jul 18, 2008

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

G

Discussion Starter · #9 · Jul 21, 2008

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

G

Discussion Starter · #10 · Jul 21, 2008

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

lcaillo

· #11 · Jul 21, 2008

What error code do you get when it shuts down?

G

Discussion Starter · #12 · Jul 21, 2008

None.
Green light ignites, lasts 1.5 seconds and extinguishes without flashing.

G

Discussion Starter · #13 · Jul 21, 2008

Could code be flashing during time frame between plugging set into duplex receptacle and walking around TV to the front?

lcaillo

· #14 · Jul 21, 2008

After it shuts down, press the input and menu buttons simultaneously for 5 seconds then not the two digit code that it flashes.

G

Discussion Starter · #15 · Jul 21, 2008

OK, sounds like you've done this before.
However, I'd expect power supply capacitors to discharge after system shut down,
making any light ignition iffy.
Board currently on workbench and TV at parent's house.
Will make a trip as time avails and report back.
Thanks for your valuable assistance Icaillo.
Working late, aren't you? Ha Ha

Dave A

G

Discussion Starter · #16 · Jul 21, 2008

I'am haveing the same problem. Hit the power button, light comes on, I can hear a faint clicking sound, than it turns off. This all take about 2-3 secounds, I cant get it to display any kind of error code. I did find 1 pico fuse blew, and it had a bad convergence chip. I swaped out the pico fuse and the chips, checked all the solder joints, and all connections. But I still cant get it to power up...:surrender:. Could it be that the caps are toast, or power supply has failed? :scratchhead:

Thanks

Mike

G

Discussion Starter · #17 · Jul 22, 2008

Hi Mike,
I'm afraid I'm still in the learning curve and won't be of much assistance.
I've traced the "The click" sound to a 12 volt enclosed relay/contactor on convergence board.
Approximately 2" right of the word COLD at rear of board.
If I understand Icaillo correctly, the flashing error code should appear 5 seconds after depressing input and menu buttons simultaneously, even if power is off but set plugged into duplex receptacle.
Schedule still hasn't permitted board replacement for this test.
Did you try same thing?

Dave

G

Discussion Starter · #18 · Jul 22, 2008

I will try it when I get home tonight around 4 clock pm.
Posted via Mobile Device

G

Discussion Starter · #19 · Jul 22, 2008

Mike,
Here's an excerpt from technical manual that may be of assistance:

1. Initial Control Circuitry Check
Immediately after the TV is connected to an AC power source:
• The LED flashes three times ... indicating the Microprocessor has initialized and is functioning
properly.
• If the LED does not flash ... the Microprocessor is NOT functioning.

2. Error Code Operational Check
Pressing the front panel “INPUT” and “MENU” buttons at the same time, and holding for 5 seconds,
activates the Error Code Mode. The LED flashes denoting a two digit Error Code, or indicating no problem has occurred since the last Initialization.
Note: The front panel buttons must used, NOT those on the Remote Control.
• The number of flashes indicates the value of the MSD (tens digit) of the Error Code.
• The flashing then pauses for approximately 1/2 second.
• The LED then flashes indicating the value of the LSD (ones digit) of the Error Code.
• The Error Code is repeated a total of 5 times.
Example: If the Error Code is “24”, the LED will flash two times, pause, and then flash four
times.

3. Error Codes
The Error Code designations indicating a malfunction, or no malfunction, are listed below:
“12” ... indicates no error has occurred.
“21” ... X-Ray Protect circuit.
“22” ... Short Protect circuit.
“23” ... Horizontal Deflection failure.
“24” ... Vertical Deflection failure.

Hope it helps

Dave A

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G

Discussion Starter · #20 · Jul 23, 2008

Okay so I tried it tonight, the set did spit out a code. 1-2 wich doesnt make sense to me. Because that means there is no errors. So what the **** is going on:thud:. Could it be that the relay has gone bad? If any one can help stear me in the right direction, that would be awsome.

Thanks

Mike:surrender:

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