Inspired by the small amount of progress I made re-soldering a bridging wire, I figured I would try that some more. I re-soldered all the bridging wires in the VS/VA section of the board. Including the trace to the VS_DET pin on chip MCV14A. That trace was mainly bridging wires but also included half a dozen SMD resistors.
I can now get up to 215 volts now before it clicks which is well above the 205 required by the TV.
Power supply repaired. (well, repaired enough for me)
But the increased voltage didn't fix the red shadows on the TV, I tried upping the voltage to 210 and it made zero difference. I tried re-seating all the ribbon cables to the logic board and now the shadows are yellow instead of red..... I'm sure it's just an issue with the ribbon cables so I will keep working on that.
Anyway, the issue this thread was started for is fixed.
I couldn't find a schematic for BN44-00446A anywhere but the board seems to be a mash up for the following 2 schematics that are readily available - BN44-00333A and BN44-00508B
The values for the components don't match but they helped me work out the layout of the board. Especially with the microcontrollers.
In the end this is effectively all I did.
- Replaced all the smaller electrolytic capacitors - The board used to stay on for a little while if it hadn't been turned on for a day, after changing these it just clicked all the time.
- Replaced 1 small blue MKT capacitor near the VS pot - I don't think this really did anything.
- I didn't replace any of the 450 volt 68uF or 250 volt 180uF capacitors. - They tested ok with an ESR meter and most of the smaller caps I replaced did too.
- Refreshed the solder on all the transformers - I did this very early on and it didn't do anything.
- Refreshed the solder on all the bridging wires in the VA/VS section and along the trace to the VS_DET pin on MCV14A - This seemed to be what fixed it.
I don't know why that fixed it. One thing I did notice though is after refreshing the solder in the VS section, the VS Pot was more sensitive. Smaller turns increased the voltage a lot more.
Hopefully my suffering helps someone else in future. Although this TV is that old there probably isn't many left.
I'm just fixing it for a mate to put in his shed
He is going to owe me a few beers if I can sort out this red/yellow shadow problem!
edit: I cleaned the ribbon cable connectors between the main board and the logic board and the shadows are now black :-D