Sanyo DP42848 Dead

[1beertap]

I picked up a Sanyo model# DP42848 Chassis# DP42848-00 freebie that doesn't come on. The unit's green light comes on then goes off and the sound of a relay click can be heard when on, also when cuts off. I have checked all of the power supply caps using both esr and capacitance meters and they tested fine. When I remove connector K8L located on main board, the back light comes on but still unit cuts off. I am thinking main board or tcon. Any ideas to isolate possible bad component? Attached are pictures of the boards.

[rmoody]

Re: Sanyo DP42848 Dead

I picked up a Sanyo model# DP42848 Chassis# DP42848-00 freebie that doesn't come on. The unit's green light comes on then goes off and the sound of a relay click can be heard when on, also when cuts off. I have checked all of the power supply caps using both esr and capacitance meters and they tested fine. When I remove connector K8L located on main board, the back light comes on but still unit cuts off. I am thinking main board or tcon. Any ideas to isolate possible bad component? Attached are pictures of the boards.

Usually if a Tcon is bad, the tv will still power on. I would be looking at the power supply more and possibly the inverters. Check for fuses on the inverters. Some tv's will not power on if they have a bad inverter or if the cable is now installed properly.

[rmoody]

Re: Sanyo DP42848 Dead

What is K8l cable running to? Your pictures aren't good enough for me to tell.

[1beertap]

Re: Sanyo DP42848 Dead

What is K8l cable running to? Your pictures aren't good enough for me to tell.

K8l has a black and a white wire running between the main board and CN1 on the inverter board. When I unplug this at the main board the backlight will come on but of course, TV does the same either way plugged in or not, won't stay on as it clicks off. I know I won't get a back light but should the TV come on with the inverter board unplugged or does the power supply need the feedback from the inverter?

[1beertap]

Re: Sanyo DP42848 Dead

Checking the power supply voltage (while unit is briefly on):

needed actual
24vdc 24.7vdc
12vdc 11.99
5vdc 5.04vdc standby

All signal grounds from power supply to chassis ground test good.

[rmoody]

Re: Sanyo DP42848 Dead

I'm not sure if it will power on with the inverter unplugged in or not. The last set i worked on would not. If your voltages coming out of the power supply are what they should be according to what is printed on the board, you know the power supply is good. Have you checked the fuses on the inverters? or the caps?

[1beertap]

Re: Sanyo DP42848 Dead

Have you checked the fuses on the inverters? or the caps?

I have checked both inverters. The fuses and caps are good.

[1beertap]

Re: Sanyo DP42848 Dead

On control board going to display. I do not have 12v when turning on tv but instead the voltage tries to build until tv shuts down. The most I've tested was about 2v. Again, it's not always the same. I do have 12v at power supply. Any ideas?

[1beertap]

Re: Sanyo DP42848 Dead

Does anyone know where I can get a schematic for this tv?

[1beertap]

Re: Sanyo DP42848 Dead

Hey guys just a little update. I thought I would try this and I can turn tv on and off a few times and after about 3sec. just before tv cycles off, I can briefly see a picture with "HDMI3" in a blue block. Would I be getting a picture if the TCON was bad? Thanks for your help.

[PlainBill]

Re: Sanyo DP42848 Dead

Hey guys just a little update. I thought I would try this and I can turn tv on and off a few times and after about 3sec. just before tv cycles off, I can briefly see a picture with "HDMI3" in a blue block. Would I be getting a picture if the TCON was bad? Thanks for your help.

Probably not. It appears you have an backlight problem.

PlainBill

[1beertap]

Re: Sanyo DP42848 Dead

Probably not. It appears you have an backlight problem.

PlainBill, thanks for taking the time to help us learn. See attached photo. When I disconnect this connector (K8L) with two wires (one black and one white) off of the main board, the backlights will come on when the tv is first turned on. It stays on until the tv cycles off. Is there a reason why the backlights come on this way? I'm pretty sure that this connection (K8L) is for a sensing/feedback line.

[PlainBill]

Re: Sanyo DP42848 Dead

PlainBill, thanks for taking the time to help us learn. See attached photo. When I disconnect this connector (K8L) with two wires (one black and one white) off of the main board, the backlights will come on when the tv is first turned on. It stays on until the tv cycles off. Is there a reason why the backlights come on this way? I'm pretty sure that this connection (K8L) is for a sensing/feedback line.

Good job of troubleshooting. Let's see if I can explain this coherently. Usually there are two control lines going to an inverter - On/Off and Brightness. There may also be a status (error) line returning from the inverter. The usual design is that the main board drives the two inputs. It is very easy for the design engineers to add a high value resistor to turn the inverter on if the input cable is disconnected. It is such a good idea I'm a little surprised more inverters don't have that feature.

Of course, that kicks the problem back to me, to explain WHY the main board is holding the inverter off. And I honestly can say I don't have any idea. I know my way around power supplies, I'm barely bright enough to troubleshoot a main board with a schematic; no way am I going to tackle a main board without a schematic.

PlainBill

[1beertap]

Re: Sanyo DP42848 Dead

PlainBill, I'm going replace the main board because like you, it's difficult to work on main board without a schematic. It'll be a 50/50 shot in the dark. Thanks for the information. I'll keep you and others posted on the results as soon as the replacement board arrives.

[dumpystig]

Re: Sanyo DP42848 Dead

I had a similar intermittent fault (also on a Sanyo, Vestel PSU and Signal board). Inverter/backlights would power up for a split second then turn off - TV would then go into fault mode with the dreaded flashing LED. After much head scratching and fault finding I had one more idea - it was a last resort and it worked a treat, I suggest you try this yourself.

On the interconnect between the PSU and Signal board I removed the female receptacle from within the moulded sockets at each end of the wiring for the BL-ON wire (I did this on all the wires, but this particular one was the solution for me). This was fiddly as f*ck but once removed I then used a sewing needle to push the inner clip of the brass receptacle so it would have a more positive grip on the corresponding pin within the plug on the board at each end. Once reconnected and powered up my set now works as it should. Been running it for 9 days now with no probs whatsoever. Like I said, it's a very fiddly task but in my case it's been well worth it.

[1beertap]

Re: Sanyo DP42848 Dead

I had a similar intermittent fault (also on a Sanyo, Vestel PSU and Signal board). Inverter/backlights would power up for a split second then turn off - TV would then go into fault mode with the dreaded flashing LED. After much head scratching and fault finding I had one more idea - it was a last resort and it worked a treat, I suggest you try this yourself.

On the interconnect between the PSU and Signal board I removed the female receptacle from within the moulded sockets at each end of the wiring for the BL-ON wire (I did this on all the wires, but this particular one was the solution for me). This was fiddly as f*ck but once removed I then used a sewing needle to push the inner clip of the brass receptacle so it would have a more positive grip on the corresponding pin within the plug on the board at each end. Once reconnected and powered up my set now works as it should. Been running it for 9 days now with no probs whatsoever. Like I said, it's a very fiddly task but in my case it's been well worth it.

Thanks for your input, but I don't get a flashing green led on this unit. When the tv is on, the green led is on and when the tv cycles off, green led is off. I did try what you suggested though but with no success.

[dumpystig]

Re: Sanyo DP42848 Dead

Thanks for your input, but I don't get a flashing green led on this unit. When the tv is on, the green led is on and when the tv cycles off, green led is off. I did try what you suggested though but with no success.

My apologies - I misunderstood your original problem. Guess I need my sleep now...

[1beertap]

Re: Sanyo DP42848 Dead

After replacing the main board with a new one, I am happy to report that the tv is now working. I wish I could fix it to the component level, but without a schematic forget it. Thanks again guys for your help.

[dumpystig]

Re: Sanyo DP42848 Dead

At least you did fix it - much more fun and plenty cheaper than paying someone else to do the job.

[amfornal]

Re: Sanyo DP42848 Dead

I have this same TV. I am a novice at electronics so please forgive me if I ask something stupid. My TV just went out last week. TV will power on, (get green light up front) and I get sound but no picture. I have taken the cover off and briefly looked at all the components and can't find any " busted caps" anywhere. I have taken good pictures of all the components and going to post soon. In the mean time, anyone have any ideas?: