I'm trying to fix a Toshiba 30" TV that a friend has given me, mainly as an exercise to see if I can. So far it is an unsuccessful exercise.
The problem:
When you apply power to the TV the standby light goes red, then after a couple of seconds it turns blue. The backlights fire briefly but then go out. There is no picture. The blue light remains on, but there is nothing else- no picture, no sound, nothing else.
Clues:
PSU:
I've attached a picture of the PSU I nabbed from someone's eBay listing for a replacement. As you can see it has two outputs that go into the main board, both labelled as 24V. One is going the entire time the set is powered. The other is only turned on when the TV is turning on, and I think powers the inverter board. The voltages are at 24V according to my multimeter.
I've tested the caps on the secondary sides, and they are all good caps.
The PSU maybe makes a slight crackling noise when the second power supply is going.
Inverter board:
I've attached a picture of the inverter board- this is exactly the same as the one in the TV.
I've tested all of the transformers and all of the resistances of each of the coils are correct.
I've tried firing it up with one backlight attached per time and all of the backlights fire at least a bit, before shutting down. I don't have a spare tube.
The inverter board has a couple of connectors for power input. The top one has the power from the main board, and also the turn-on, turn-off signal. I think the bottom one is turned on and off by the main board when it wants to fire up the lamps.
I've put an oscilloscope on the power input to the inverter board (the second connector, without the on-off signal or other information from the main board). It's a fairly flat 24v when it is on, except when it's trying to fire the lamps when you get a 3v ripple on it.
What would you do?
Ask if my ramblings don't make any sense.
The problem:
When you apply power to the TV the standby light goes red, then after a couple of seconds it turns blue. The backlights fire briefly but then go out. There is no picture. The blue light remains on, but there is nothing else- no picture, no sound, nothing else.
Clues:
PSU:
I've attached a picture of the PSU I nabbed from someone's eBay listing for a replacement. As you can see it has two outputs that go into the main board, both labelled as 24V. One is going the entire time the set is powered. The other is only turned on when the TV is turning on, and I think powers the inverter board. The voltages are at 24V according to my multimeter.
I've tested the caps on the secondary sides, and they are all good caps.
The PSU maybe makes a slight crackling noise when the second power supply is going.
Inverter board:
I've attached a picture of the inverter board- this is exactly the same as the one in the TV.
I've tested all of the transformers and all of the resistances of each of the coils are correct.
I've tried firing it up with one backlight attached per time and all of the backlights fire at least a bit, before shutting down. I don't have a spare tube.
The inverter board has a couple of connectors for power input. The top one has the power from the main board, and also the turn-on, turn-off signal. I think the bottom one is turned on and off by the main board when it wants to fire up the lamps.
I've put an oscilloscope on the power input to the inverter board (the second connector, without the on-off signal or other information from the main board). It's a fairly flat 24v when it is on, except when it's trying to fire the lamps when you get a 3v ripple on it.
What would you do?
Ask if my ramblings don't make any sense.
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