Mitsubishi Rear Projection TV Shutdown - X-Ray Protection

Intro

Yes, this is for a late 80's to early 90's big, bulky rear projection set. I had it re-aligned a few years ago and it's (almost) on par with a plasma set. But it started turning off within an hour of startup ... hence my quest to repair it.

On-line Resources

I found the service manual on-line. I'll leave it to you to find a source that isn't a hack-fest. Search for "Mitsubishi Service Manual 48311 pdf" or similar. I list the models that the manual supports at the end.

Also, I found a thread on justanswer.com that suggested this fix.

Blink Codes (page 24)

1. On AC power-up, the front panel LED will blink 3 time if the microprocessor is operational.
   
2. Press the FRONT PANEL!  INPUT + MENU buttons for 5 seconds then watch the LED for the blink code(s). 21 is for X-Ray Protect circuit.

The thread on justanswer.com suggested that capacitor C5A64 was the likely problem. Here's the circuit from page 65:

In short, I checked C5A64, a Nichicon 22µF, 16V electrolytic capacitor. ESR was between 4.7 and 5Ω and the capacitance was within spec. I replaced it with a Panasonic cap with an ESR of 3.0Ω. The set has been running for a couple of hours now so I'm hopeful that I can button it up soon.

Accessing the Circuit Board

The access process is as follows:

1. Unplug the set and give it an hour so so for the capacitors to discharge. It may take more or less time, you be the judge. And just stay away from display tubes and flyback capacitors in general.
   
2. Remove the Phillips head screws around the "Back Board" lower back panel/cover, the I/O panel, and the AC power inlet.
3. On the bottom are 3 boards mounted in a frame that slides back. Most cables are bundled and tied back with "twisty" nylon cable supports. You'll need to free those cables to slide the board frame back. Some leads are too tight and will have to be disconnected to allow the frame more travel. They are the I/O panel connector and one its cable coming through a noise suppressor.
4. There's a long black screw on the rear edge (toward you) of the frame that keeps the frame from moving. Remove it.
5. Lift up on the side latches forward of the flat frame areas labeled "HANDLE", and pull the board frame toward you.

Removing the Board

 The X-Ray circuit is on the right-most Power Board (page 18) as viewed from the rear.

1. Disconnect the 3 flat ribbon connectors by lifting UP on the right-hand side CONNECTOR via the little white tabs on the top. I had to use small channel lock pliers to GENTLY grasp the tabs and GENTLY wiggle some of the connectors loose.
2. There are 4 PH screws that hold the board down; 2 in the center, 2 on the right.
3. There are tabs along the top, bottom, and left edges that need to be sprung back to release the board to pivot to the right, then out.

Capacitor C5A64 is near the edge of the board, center right behind the transformer shield as I recall. Near 20-pin DIP IC5A02. EXACT location and photo PENDING.

Conclusion

I hope this helps someone that want to keep their set in service (despite the lack of HDMI!).

I didn't test many other components, or test reference voltages with the set powered up - the cabling just wasn't long enough for me to access the area easily and what I judged to be safely.

Models Supported by the Referenced Service Manual

V20A Models: VS-50111 VS-60111
V20C Models: WS-48311 WS-55311 WS-65311 WS-55411 WS-65411 WS-73411
V20C+ Models: WS-55411 WS-65411 WS-73411