Not getting AC DET on plasma

[joshbsg]

I have a Zenith 50" plasma. Model: Z50PJ240-UB

Set turns on and right back off. I found a training manual to test the SMPS. I am not receiving the 4.44 on the AC DET line. According to the manual the AC DET is collected from the Ac line rectified and then routed to the IC701. The IC then sends 4.44 on pin 16 to the main board. As long as 4.44 remains the tv functions. If AC DET is lost set shuts off.

I want to test the rectifying circuit but cant identify where it is on the PSU.

Any help would be appreciated

[Ltank]

Re: Not getting AC DET on plasma

Who makes the P.S.? Samsung or LG? Is there part number on the board? Got a good Pic?

[paulstef]

Re: Not getting AC DET on plasma

I have a Zenith 50" plasma. Model: Z50PJ240-UB

Set turns on and right back off. I found a training manual to test the SMPS. I am not receiving the 4.44 on the AC DET line. According to the manual the AC DET is collected from the Ac line rectified and then routed to the IC701. The IC then sends 4.44 on pin 16 to the main board. As long as 4.44 remains the tv functions. If AC DET is lost set shuts off.

I want to test the rectifying circuit but cant identify where it is on the PSU.

Any help would be appreciated

In the training manual you'll find that you can turn on the PSU if you disconnect the mainboard OR if you disconnect the mainboard and then manually put resistors from 5V to RL_ON and M_ON .

This will turn on both relays and then 5V VS VA etc.

The PSU will stay on.

They recommend putting a load on VS even though it works without it too.

AC_DET is indicated as being an output on the page that says: "Signal and Voltage Distribution Block". If I follow the trace it comes from pin 2 of IC701 of the PSU, i.e. the uC IC701 detects if there is AC somewhere else and then activates this output.

On the primary side of the PSU you will see two long resistor chains which could both be involved in measuring incoming AC, they then go to one of the optocouplers. The resistor chains come from cathode of D103 and anode of D308. You will have to draw parts of the circuit.

[paulstef]

Re: Not getting AC DET on plasma

Who makes the P.S.? Samsung or LG? Is there part number on the board? Got a good Pic?

It's probably EAY60968701 or EAY60968801.

[paulstef]

Re: Not getting AC DET on plasma

From my other thread, yes if you are sure that the set turns of due to commands coming from the mainboard you could try to provide 5V via a resistor to the ACdet going to the mainboard. I don't think we have the same fault. Mine turns of randomly yours after 10 sec.

Remove the cable from the mainboard and the PSU should stay ON. If it doesn't the problem is on the PSU

[Ltank]

Re: Not getting AC DET on plasma

With the Main board disconnected the P.S. runs ok? You would find the main board telling it to shut down for some reason. Carefully inspect inspect main board visually and check voltages on all its connectors

[joshbsg]

Re: Not getting AC DET on plasma

PCB:EAX61397101/9
PSU P/N: EAY60968701

It is not an issue with the main board. The PSU never gives AC DET whether I do static load test or not. Mainboard connected or disconnected. This is a fault on the PSU.

I also traced the AC DET through a resistor onto pin to of IC701. I cannot determine if the fault is with the IC or the rectifying circuit.

What do you suggest??

[joshbsg]

Re: Not getting AC DET on plasma

Here is the PSU

[paulstef]

Re: Not getting AC DET on plasma

If the PSU works otherwise I would just trick the mainboard like you suggested. IC701 has a 5V power supply, I assume it gives out 5V on pin 2 when activated.

I would apply 5V via a 1k resistor on to AC det on the mainboard. (R730 on PSu is 1k in my case.)

[joshbsg]

Re: Not getting AC DET on plasma

Paulstef:
The PSU 'never' gives the AC DET. Here is a pic. You can see where AC DET goes up to IC701 through a 1k resistor labeled R730.

If I tricked the mainboard by supplying 5 volts on that line it would not tell the tv to turn off. However, where can I steal 5 volts from on the PSU?

[joshbsg]

Re: Not getting AC DET on plasma

Im not sure that IC701 is getting the voltage to send down to AC DET. The resitor and path from IC701 is good. This has to be an issue with the IC701 or the rectifing circuit that supplies the voltage to the IC to give to the mainboard.

What do you suggest?

[joshbsg]

Re: Not getting AC DET on plasma

Are you suggesting bridge on the mainboard or PSU?

[paulstef]

Re: Not getting AC DET on plasma

From what I understand it works like this:

If the signal AC_DET does not go to the uC on the mainboard then the uC on the mainboard will shutdown M_ON and possibly RL_ON.

Agreed on that?

Therefore if you desolder the resistor terminal that goes to pin 2 of IC701 and connect 5V to that resistor the uC on the mainboard will get it's AC_DET. Pin 2 of IC701 will not be connected anymore.

You can take 5V from P813 from either 5V1 or M_ON (which will be on once the mainboard sends the signal).

[Neelix]

Re: Not getting AC DET on plasma

I looked, but could find find the service manual for free download. Would be interesting to find out why you're not getting the right AC_DET voltage, but without a diagram it is difficult. IC701 also look like one of those programmable processors. So even if you find datahseet for the processor, it won't do much good

[paulstef]

Re: Not getting AC DET on plasma

The most likely to detect AC seems to be right after RL101.

The mainboard turns on both relays, if AC has the right voltage PC102 should be ON. You should then get 5V on pin 28 of IC701.
These diagrams is all I have so far.

[veikra]

Re: Not getting AC DET on plasma

Well, im digging in those drawings for mine. I had the typical 3br infineon problem. click on, click off, red del slowly dim and restart.

I changed 3br chip, worked a while, started doing the same thing. pull board out, test bench now it does something else. Obviously, infineon chip isnt issue.

now rl101 click on and off every second. Different problem

my ic701 is a v1.1a-1a93, the repair kit had a v1.2a-d99d . I replaced it and no clicking now. put back the original, back to clicking fast.

So I went backward, fast clicking is worst, the second relay doesnt click anymore...

Im wondering if it's ic701 and the new part isnt compatible.