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Bush LCD32TV005HD PSU blown, no picture after PSU fixed

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wellij81:
Hi,

I wonder if anyone can help please? I have a Bush 32" LCD which had a blown PSU (24V rail gone, 12V ok.) I suspected the switching control IC, so I swapped them (same IC on each rail), so now 24V ok, 12V gone. Using a bench PSU to supply the 12V rail, it responds to remote control by flashing the red LED and the PSU control line goes in and out of standby in response to the remote, but there is no picture and no on-screen menu. The backlights work and the supply rails are ok. I haven't been able to find a manual, so it is hard to fault-find the main PCB. Has anyone got any tips?
I have read other posts about the LCD panel connector being dodgy, but I have reseated that. It all looks ok, no burnt bits, no bulging caps, but something must have taken out the PSU.

Thanks,

Jonathan

tv tony:
i have one on the bench at the moment, there are two versions, one with the audio out on the psu, one without, which is yours?

wellij81:
Hi Tony,

Thanks for the reply - I was beginning to wonder if anyone was out there! Mine has the audio out from the main PCB, not the PSU. The PSU says Beko Z1J.194-04. The main PCB says Beko Z1J190R-6. I have downloaded the service manual from this site. It seems to be the same as the Beko LM chassis. I have checked all the regulators on the main PCB and they are all producing the correct voltages, such as 8v, 5v, 3.3v, 2.5v and 1.8v, which is a bit worrying.
Any ideas?

Thanks,

Jonathan

wellij81:
Some progress. I removed the upper chassis plate to get to the LCD driver PCB, and found a burnt 100 ohm resistor and burnt smd diode. I didn't have the right diode so I bodged two 1N4148's onto the PCB and replaced the 100 ohm resistor. To my amazement I got a picture! Unfortunately the 24v side of the PSU gave up so had to run both rails from bench PSU's, which caused the backlights to flicker probably due to lack of current from 5A PSU. Even so, I got it to tune in a station and got pictures and sound. Now all I've got to do is fix the PSU. The LCD driver board is available for £55 from SJS, but hopefully the bodge will last.

Jonathan

tv tony:
well done but the diode is a zener that hols the supply steady, there is a 5v screen and a 12v used, i would fit one pronto, the last thing you need is a lcd drive pcb giving up on you
regards

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