Pioneer PDP-LX508D Won't turn on, 3 flashes from PSU

[niblettr]

Bought this in the hope of fixing would like some pointers.

When i plug in mains chord I get 2 clicks from the relay. (sounds about right to me) When i try an get the tv out of standby, a relay clicks the i get 3 flashes from red led on PSU.

|v'e done a visual inspection and can't find anything suspicious.

There are some pen markings on some of the Ybuffer ICS??

[ReeceyBurger123]

Re: Pioneer PDP-LX508D Won't turn on, 3 flashes from PSU

Hello these are great Tv's deffo worth repairing. Does the standby light on the front of the Tv give any flashes ? If so are they red or blue and how many does it give ?

[niblettr]

Re: Pioneer PDP-LX508D Won't turn on, 3 flashes from PSU

red and orange when in stanbye,
red and blue with fault then contiuous 2 red flashes

[ReeceyBurger123]

Re: Pioneer PDP-LX508D Won't turn on, 3 flashes from PSU

2 red is a Ydrive failure which causes the Vs rail to be dragged down on the Psu therefore locking out the Psu. If you unplug the Y and Xdrive what happens does the Tv flash another fault code ?

[niblettr]

Re: Pioneer PDP-LX508D Won't turn on, 3 flashes from PSU

No change, same flash codes.

[ReeceyBurger123]

Re: Pioneer PDP-LX508D Won't turn on, 3 flashes from PSU

Ok now time to start checking the voltage rails from what they are stated as on the connectors.

[niblettr]

Re: Pioneer PDP-LX508D Won't turn on, 3 flashes from PSU

Ok now time to start checking the voltage rails from what they are stated as on the connectors.

Ok, got no VSUS even when isolated. PSU fault?

[tom66]

Re: Pioneer PDP-LX508D Won't turn on, 3 flashes from PSU

Seems likely

[niblettr]

Re: Pioneer PDP-LX508D Won't turn on, 3 flashes from PSU

ok, found 2x K3314 FETS that are shorted on the middle heatsink on the PSU.
I've whipped them out and double checked and there are shorted. Ordered some new one.
Bit worried that something further upstream may be bust.
I checked some sot23 transitors that looks like may be driving these fets and they checked out ok but 2 diodes measured a bit odd. I got 0.6v drop in both directions....

[tom66]

Re: Pioneer PDP-LX508D Won't turn on, 3 flashes from PSU

You should replace the driver chip (connected to the FETs) and the fuse as well.

[ReeceyBurger123]

Re: Pioneer PDP-LX508D Won't turn on, 3 flashes from PSU

Probably just the fets quite common on Plasma supplies due to the way they are loaded at start up. Also replace the fuse and should be fine

[tom66]

Re: Pioneer PDP-LX508D Won't turn on, 3 flashes from PSU

Probably just the fets quite common on Plasma supplies due to the way they are loaded at start up. Also replace the fuse and should be fine

You should know now that it is a bad idea to just replace the FETs! Also the startup loading isn't a big deal (just charging the caps, but there is a current limit for a reason.)

[ReeceyBurger123]

Re: Pioneer PDP-LX508D Won't turn on, 3 flashes from PSU

Alot of the time in my case the driver has almost never ever been damaged at all Tom. Normally if the Vcc and other input pins have no shorts or low resistance across them or to ground it will be ok. I personally have only had to replace 1in 10 drivers for the repairs like this.

It might come back and bit me on the ass but I will sort it.

[niblettr]

Re: Pioneer PDP-LX508D Won't turn on, 3 flashes from PSU

thanks for all the input so far.
What fuse?

[niblettr]

Re: Pioneer PDP-LX508D Won't turn on, 3 flashes from PSU

note I also removed the transformer so that I could get to the screws holding the fets to the heatsink.

[tom66]

Re: Pioneer PDP-LX508D Won't turn on, 3 flashes from PSU

Alot of the time in my case the driver has almost never ever been damaged at all Tom. Normally if the Vcc and other input pins have no shorts or low resistance across them or to ground it will be ok. I personally have only had to replace 1in 10 drivers for the repairs like this.

It might come back and bit me on the ass but I will sort it.

For me it's much higher - around 1 in 3 have shown suspect readings - although it does depend on the topology of the supply. Flyback and half bridge is more likely to damage the driver. Flyback due to high peak drain voltages, half bridge due to floating source node

[ReeceyBurger123]

Re: Pioneer PDP-LX508D Won't turn on, 3 flashes from PSU

For me it's much higher - around 1 in 3 have shown suspect readings - although it does depend on the topology of the supply. Flyback and half bridge is more likely to damage the driver. Flyback due to high peak drain voltages, half bridge due to floating source node

Thats true, I have been lucky so far but I always check them any way Tom I know what too look out for. I guess there is the cases of the controller becoming intermittent as I have had before but thats rare for SMPS tbh.

[niblettr]

Re: Pioneer PDP-LX508D Won't turn on, 3 flashes from PSU

Sorry guys, what fuse? Do you mean the sub ohms ceramic resistors?

[niblettr]

Re: Pioneer PDP-LX508D Won't turn on, 3 flashes from PSU

Sorry guys, what fuse?

[ReeceyBurger123]

Re: Pioneer PDP-LX508D Won't turn on, 3 flashes from PSU

Normally for the Vs fets its in between the filter caps or behind the fets. It might be a ceramic style can fuse.