Mitsubishi WD-73835 73" Fixed

[CalebG]

Just thought I would post this as a help to anyone with a similar issue. One of my coworkers moved his tv and it wouldn't turn on after the move. Isolated to the main power board as there was no standby power to switches but no blown fuses. After a bit of detective work I found resistor R9A20 (68k) was open, it is the vcc feed for the chopper.
**broken link removed**

 

[Nigel Goodwin]

After a bit of detective work I found resistor R9A20 (68k) was open, it is the vcc feed for the chopper.

I don't know if it's a cultural thing?, but I've never heard it called that - it's normally called the 'start-up resistor' - and it's a VERY common fault in switch-mode PSU's that use them. Can't comment on this particular example though, as Mitsubishi pulled out of the UK a number of years ago.

Its also quite common to have two resistors in series, which (in my experience) seems to make them fail.

 

[CalebG]

Well Im probably addressing them incorrectly, I couldn't believe a 2 cent resistor caused the tv to die, I spent a bunch of time testing everything else and finding it all good. Then spent some time pouring over the schematic and saw these two resistors and thought Aha that would cause everything. My coworker is very happy now at any rate.

 

[Nigel Goodwin]

Well Im probably addressing them incorrectly, I couldn't believe a 2 cent resistor caused the tv to die, I spent a bunch of time testing everything else and finding it all good. Then spent some time pouring over the schematic and saw these two resistors and thought Aha that would cause everything. My coworker is very happy now at any rate.

You now mention two?, was there two in series? (like I mentioned above that is common) - if so it's very important to change them both, or the other one will fail in the not too distant future.

 

[CalebG]

Do'hh I only switched out the one. I will have to switch the other one out for him. Voltage made it through the first one but the second one was open. Thanks for the heads up. Still kinda new to all this, but learning a lot.