So, this one turned up on the bench. Power light flashes, but the set won't power up. It's stuck in standby. Now, I would have thought that the main board had corrupted firmware. But, somewhat surprisingly that was not the case.
There are two faults: the main issue is the 17IPS19-4 power supply 24V isn't coming up, which is due to a FET and diode in the boost converter being shorted. Naively testing the commonly failed diodes (on the output) would lead you to suspect the diodes were shorted - but they aren't. Surprisingly, it's the diode on the output of the boost converter which is short. But, this alone wouln't account for the short on the 24V output - it would just prevent the LED strips working, the TV should still otherwise "work".
What's happened is this diode being short appears to have damaged the main boost FET for the boost stage (this is all on the secondary so no blown fuses or damage to the primary.) The boost stage takes the ~24V and boosts it to about 60-70V for the LED strip. This is shorted, preventing the 24V rail coming up, and the main board detects this fault and shuts down.
So, removed the FET and diode and sure enough now the TV turns on, and you can see a (non-backlit) image on the screen using a torch. So the set appears to only have a PSU fault. I will replace the FET and diode and see if the problem is fixed.
The only major concern I have is if that LED driver IC has been damaged (TPS61199); the FET has around 130 ohm gate-drain and gate-source (with 5 ohms drain-source) so I *think* it's going to be OK. I ohmed out the gate drive to Vcc and ground and it's about 2k to each so it doesn't look shorted. The parts are cheap so I'll just try it and see what it does. Worst case, the FET blows up again, but it's not expensive.
These power supplies, whilst cheaply made with the cheapest off the shelf components, don't look TOO bad, especially when you compare them to a PW25-4.... frankly, I'd take a million of these over a single more PW25-4...!
It's kinda weird jumping from a 9G KURO to the cheapest of the cheapest Vestel LED models. And the terrible thing is, Pioneer are now whoring their name out to dodgy OEMs... and there's talk of a Pioneer LED set based on a Vestel chassis...
There are two faults: the main issue is the 17IPS19-4 power supply 24V isn't coming up, which is due to a FET and diode in the boost converter being shorted. Naively testing the commonly failed diodes (on the output) would lead you to suspect the diodes were shorted - but they aren't. Surprisingly, it's the diode on the output of the boost converter which is short. But, this alone wouln't account for the short on the 24V output - it would just prevent the LED strips working, the TV should still otherwise "work".
What's happened is this diode being short appears to have damaged the main boost FET for the boost stage (this is all on the secondary so no blown fuses or damage to the primary.) The boost stage takes the ~24V and boosts it to about 60-70V for the LED strip. This is shorted, preventing the 24V rail coming up, and the main board detects this fault and shuts down.
So, removed the FET and diode and sure enough now the TV turns on, and you can see a (non-backlit) image on the screen using a torch. So the set appears to only have a PSU fault. I will replace the FET and diode and see if the problem is fixed.
The only major concern I have is if that LED driver IC has been damaged (TPS61199); the FET has around 130 ohm gate-drain and gate-source (with 5 ohms drain-source) so I *think* it's going to be OK. I ohmed out the gate drive to Vcc and ground and it's about 2k to each so it doesn't look shorted. The parts are cheap so I'll just try it and see what it does. Worst case, the FET blows up again, but it's not expensive.
These power supplies, whilst cheaply made with the cheapest off the shelf components, don't look TOO bad, especially when you compare them to a PW25-4.... frankly, I'd take a million of these over a single more PW25-4...!
It's kinda weird jumping from a 9G KURO to the cheapest of the cheapest Vestel LED models. And the terrible thing is, Pioneer are now whoring their name out to dodgy OEMs... and there's talk of a Pioneer LED set based on a Vestel chassis...
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