Toshiba 52XV645U shuts off when signal is connected.

[johnboy1313]

I picked this TV up on Tuesday. It wouldn't turn on when I bought it. I got it home and plugged it in and it powered on. I emailed the seller to ask if this had happened before. He said it had. Once, it stayed on for twenty minutes. Another time, it stayed on for 4 hours. Who knows if this is true or not. At any rate. Without a signal connected. It seems to come on and shut off fine. However, it will not turn on if the HDMI is connected to any of the HDMI inputs. It shuts off after a few seconds when using A/V inputs. I believe this points to a main board issue. When the set is working, POW_PRT, POW_SIG, AC_DET, and POW_LCD all show 3.0V. When the set isn't working, POW_SIG and POW_LCD drop out. Here are some pics.

[tom66]

Re: Toshiba 52XV645U shuts off when signal is connected.

What does it do on digital tuner?

[Ltank]

Re: Toshiba 52XV645U shuts off when signal is connected.

I would check for a damaged HDMI port. Pin # 17 Gnd, #18 +5vdc, #19 Hot Plug Detect. Try plugging into the other HDMI port and see if it works OK

[johnboy1313]

Re: Toshiba 52XV645U shuts off when signal is connected.

What does it do on digital tuner?

I don't know. We don't have a digital antenna.

[johnboy1313]

Re: Toshiba 52XV645U shuts off when signal is connected.

I would check for a damaged HDMI port. Pin # 17 Gnd, #18 +5vdc, #19 Hot Plug Detect. Try plugging into the other HDMI port and see if it works OK

It shuts off when using any of the three HDMI ports.

[Ltank]

Re: Toshiba 52XV645U shuts off when signal is connected.

HDMI Port Pic

[johnboy1313]

Re: Toshiba 52XV645U shuts off when signal is connected.

It shuts off using any of the inputs. Right now there is nothing connected and it won't turn on. On the occasions that it does turn on, the PSU relays click and the green LED lights on the main board. When it won't turn on, the relays click and the LED won't light.

[tom66]

Re: Toshiba 52XV645U shuts off when signal is connected.

I would try updating firmware, if it has USB.

[johnboy1313]

Re: Toshiba 52XV645U shuts off when signal is connected.

Right on. Will do. I'll let you know.

[johnboy1313]

Re: Toshiba 52XV645U shuts off when signal is connected.

I'm trying to update the firmware according to the instructions on Toshiba's website. Unfortunately, the power LED blinks three times, twice, stays lit for about two seconds, then the entire set shuts down again. This has been happening all day. It looks like I may have to do a little digging before I can even attempt the update.

[johnboy1313]

Re: Toshiba 52XV645U shuts off when signal is connected.

Put a used main in. Same problem. Not sure where to go from here.

[johnboy1313]

Re: Toshiba 52XV645U shuts off when signal is connected.

I'm back with an update on this one. Eventually it got to the point that this one wouldn't turn on at all. The LED on the front would blink three groups of three times, then go solid, then go out. I found a 40xv645u (same main, different PSU) with a cracked screen on Craigslist. I put the main board in and had the same blinking LED with no power. Like I said, the PSU is slightly different than the original, but will still fit inside the chasis using the same screw holes. It also has all of the proper connectors, two to the main board and one to each inverter. All pins are labeled the same as well. I put it in, just to see what would happen and the set came to life and works now. The original 52" TV uses 18 bulbs, the 40" only uses 14. I suspect there will be some issue with current draw or something like that, if not though, can I just keep the PSU for the 40" in the 52"?

The first pic is the 40" PSU, the second is the original, the third is the 40" PSU installed in the 52" TV. I apologize for the quality of the third pic, it was late and I didn't realize how crappy it was until this morning.

[johnboy1313]

Re: Toshiba 52XV645U shuts off when signal is connected.

Any ideas?

[dkneyle]

Re: Toshiba 52XV645U shuts off when signal is connected.

Well, it seems that you identified that the original power supply was the problem at least. I would think that the 40 inch power supply would be close to overloaded, but then again they've got pretty good regulation on these SMPS and if the heatsinking was adequate it might keep going.
On that original board I'd be looking for bad joints in the vicinity of the semi-conductor devices connected to the heatsinks. From your description it sounds like something giving up as things warm up or extra current is drawn. There's a regulating IC that is marked IC551 I think? I'm growing increasungly suspicious of the types of devices the more I get into this hobby. If it's the same on device on both boards you could even do a swap over? Also, check that big diode out that's next to the Regulating IC. It'll be a fast-switching device. You might need to lift a leg to properly check that one.

[johnboy1313]

Re: Toshiba 52XV645U shuts off when signal is connected.

I found this repair kit on eBay.

http://www.ebay.com/itm/Power-Supply...item1e83af0b86

It includes D820, R850, and "upgraded" R827 and R828. I checked my D820 and don't see any shorts, R850 appears to be OK as well, but both R827 and R828 show signs of getting really hot. I tried to get a picture. The board under the resistor is really dark. It looks alot worse in person. Yet, both resistors show 47 ohms.

[johnboy1313]

Re: Toshiba 52XV645U shuts off when signal is connected.

Anyone else have any thoughts?

[dkneyle]

Re: Toshiba 52XV645U shuts off when signal is connected.

I notice he says that kit is only if the TV is COMPLETELY DEAD. Which yours wasn't really. Those overheating resistors certainly could do with upgrading - seems like a design fault. How do the joints look? Overheating components can lead to cracked joints due to expansion and contraction which in turn gives you a thermal fault.

[johnboy1313]

Re: Toshiba 52XV645U shuts off when signal is connected.

I will definitely look into that. Thanks for the tip. At this point, with the orignal PSU, the TV is practically dead. When you plug it in, the LED flashes briefly and then shuts off. Unfortunately, the 40" PSU has none of the parts in the kit to see if that would help.

[dkneyle]

Re: Toshiba 52XV645U shuts off when signal is connected.

Of all the boards that are easiest to fault find, the PSU is it (I reckon anyway). There is a sequence to follow (which Tom or others will no doubt correct or elaborate on) which is basically:
1. Do you have the correct voltage across the big caps on the primary side, which will be of the order of 350 VDC. This tells you if the first stage of the power supply where the mains is rectified is working OK. Check also to see if there is excessive AC ripple which would be an indication of whether these big caps have dropped their bundle.
2. Do you have the standby supply (~5VDC) OK? This has its own sub-regulator stage. On yours it looks like it's working cause you get those flashing LEDS, but check all the same.
3. An 'on' signal comes back from the mainboard to tell the PSU to supply the higher voltages: ~12VDC that runs most of the circuitry. We can assume your 'On' signal is OK because the TV works OK with the other board. Which suggests it's probably something in that 12V regulator section of the SMPS.

I like to use the compare and contrast approach. Usually there will be 4 MOSFETs in that 12 V regulator stage for the high frequency switching. Use the diode function on your meter and see if they all measure the same. Be very suspicious if you see zero ohms across any of the junctions. The other usual suspects are the electros (obviously) and any regulating IC connected to a heat sink.

[johnboy1313]

Re: Toshiba 52XV645U shuts off when signal is connected.

dkneyle, thanks for your help with this. Had a long weekend that included a wedding and a hangover so I didn't get to the TV like I had hoped. I will get the voltages tonight. I have checked all FET's and haven't seen anything out of sorts yet. I do have another question regarding the two PSU's though.

As I said before, the 40" TV has 14 bulbs using one inverter with two 7A fuses mounted on it. The 52" TV has 18 bulbs using two inverters, each with one 7A fuse on it. I assume that the two fuses on the 40" inverter are independent of each other just as the fuse on the master inverter of the 52" is independent of the fuse on the slave.

My question is, if there are two 7A fuses in either circuit, does that mean that the 40" PSU should be able to safely handle the current draw from the 52" circuit? At least in the 24V section of the PSU. I haven't looked to see what the fuses on each T-Con can handle.