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Mitsubishi WS-65411 (V20C+ Chassis) ok sound, no video

2K views 6 replies 4 participants last post by  lcaillo 
#1 ·
A friend was getting rid of a dead Mitsubishi WS-65411 (V20C+ Chassis) TV. It has sound, but no video. I have tested both A/V and antenna inputs with the same results. The front power button doesn't seem to respond, but I can get the 1-2 (ok) service diagnostic code, it will power on using the remote, but seems to be very slow to respond to the remote. I did have the tubes light up a couple times, but when they did the image was very fuzzy 'snow' (jagged edged left-right). I have not been back to a picture in a while.

1. I replaced the C9C01 47uF/16V cap on the PCB-Signal had leaked all over the board, it didn't help.
2. Voltages seem reasonable
110VDC = 110.7VDC
30VDC = 30.1VDC
-24VDC = -25.1VDC
+24VDC = 24.7VDC
17V/12 = 19.12VDC
12 = 12.08
5 = 5.03
9VS VDC = 9.06
High voltage sounds ok (I don't have a HV probe), and the 3 CRT filaments are ok.
hot to cold ground is ~3-9mVDC, 3.6VAC
I have not scoped all these for ripple yet though given the sketchy ('theoretical' manual vs a Sam's type). The couple I checked seemed to be about 0.04-0.05VAC noise and about 0.01-0.02VAC half-sign ripple.

I have the 2002 Technical Training and Troubleshooting Guide (which is also only what Sam's sells), and the Service Manual (not as helpful, given it is more alignment/physical/high level diag.

I have searched the forums for hints, but nothing stands out.

Are there any other tech manuals or diag information? I assume Mitsubishi must do board level swaps and no field level component repairs? Sam's didn't have anything they had done for any of the V20A/V20C/V20C+ chassis sets.

Any other hints? [Other than working through the set block-diagram at a time trying to trace what might be happening. If I had a 2nd working set that might be a lot easier.]

My background is EE (&CS). I grew up doing electrical wiring and TV repair. [I am mostly a software type now ;) ]

Thanks,

-Jeff
 
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#5 ·
Good to know. :T

I might have referred to him here had I known (I try not to link to other forums when it's not needed), but if the OP wants a response sooner rather than later, I know he's active in the mega thread over there every day... not sure how often he checks in here. I haven't seen any posts from him here lately, for sure. This is in his profile here: "Last Activity: 9/22/11 12:49 PM"
 
#6 ·
Currently no rastor at all. A few times the tubes earlier did have a 'snowy' image. The RF tuners and input selection seem to work fine. The funny part is the power and volume really lag input when seen, like a processor dropping interupts and not seeing the input.

I did find V20_Schematics.pdf which says 'Service Manual' and a subtitle of Part 2: Schematic Diagrams, something really nice to had had a few hours of work ago vs trying to decide how it should be working from block diagrams only.
The schematics do have some expected voltages and a few waveforms on it. I didn't get a chance to work through any of it tonight (practicing w/ my 16yo for his finals).

If you do have hints please let me know and I will provide feedback if/when I can isolate the problem(s).

Thanks,

-Jeff
 
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