Toshiba 42HL196 - Clicking relay, Power Board

[budm]

Re: Toshiba 42HL196 - Clicking relay, Power Board

Yes. So it can easily handle the 0.5A which is a lot more than the relay was drawing.
So you can put the force on resistors back in place.
Actually you can leave this 10 Ohms in place.
If I remember correctly, the 12V needs to small load (47~56 Ohms, or two 100 Ohms in parallel will be fine) on it also.

[MEB]

Re: Toshiba 42HL196 - Clicking relay, Power Board

OK, I let the board run all night and had 5.091V standby steady this morning when I checked on it. I left the 5V load resistor connected, attached the 5V force on resistors and attached 2, 100 ohm resistors paralled which measured 50.04ohms to the same location as you attached the lightbulb in your repair post. Upon plugging in AC the 5V relay is still clicking on/off at the same rate as it previously did. Don't know why, but am having a ball trying to find out ! I did notice that the 0-5V cycling with the clicking relay is now only 0-1.8 V since I have the load on the 12V circuit I guess?

[budm]

Re: Toshiba 42HL196 - Clicking relay, Power Board

That is very strange.
Can you please check the fuse F820 to see if it is OK, if it is, then attache the DC meter probes on the two legs of the main filter cap (270uF 450VDC) to see if it jumps up and down between 160 and 360VDC or so and in sync with the clicking of the relay.

[MEB]

Re: Toshiba 42HL196 - Clicking relay, Power Board

OK, the fuse F820 reads .2 ohms in circuit. The big cap C820 reads 156-159 or so VDC but can't really tell if the fluctuation is in sync with the relay clicks, but never any higher than 159V or lower than 156 best I can tell. Thanks for sticking with me.

[budm]

Re: Toshiba 42HL196 - Clicking relay, Power Board

OK, that may explain why it is clicking, the PFC voltage booster is not coming on.
We are going to bypass the relay contact of the 5V relay to see if the PFC Voltage booster will turn on or not.
As you can see on page 2 the diagram I just posted, you are going to jump the relay contact of that 5V, you will have the meter probe attached with alligator clips so you will have free hand to plug the power cord into the AC outlet and see if the Voltage on the cap will jump to higher than 360VDC. We are testing the board by itself so it should be fine to bypass the relay for testing.

[MEB]

Re: Toshiba 42HL196 - Clicking relay, Power Board

OK, sorry it took so long, getting pretty serious here. I jumpered the contact side of the 5V relay. I connected meter pos to + and meter neg to - of the big cap C820. I plugged it in and meter goes to 159-159.5 VDC. I pulled the plug and tried it again. Meter is much more steady than in post #24, but never goes above 159.5

[budm]

Re: Toshiba 42HL196 - Clicking relay, Power Board

OK, so we know that the PFC did not start, leave everything as is but now move the meter to the 5V1 and GND and see if it is still going up and down.

[MEB]

Re: Toshiba 42HL196 - Clicking relay, Power Board

OK, yes it is, from 0-3.7VDC I'd say.

[budm]

Re: Toshiba 42HL196 - Clicking relay, Power Board

OK, that is not going to work since the Voltage (22V) for running the PFC IC is generated by the standby power supply which means the PFC will not start.
OK, right now it is the process of elimination to find out why 5V is not stable.
You have to remove or lift one leg of either D826 or R8217 (page 3), then power up and see if 5V is stable.

[MEB]

Re: Toshiba 42HL196 - Clicking relay, Power Board

I chose D826. 5V is still not stable. 0-4.5VDC

[budm]

Re: Toshiba 42HL196 - Clicking relay, Power Board

Boy! That makes no sense, we remove the voltage feeding the PFC circuits and it's still fluctuating but it does not fluctuate with 10 Ohms load (0.5A load) without the force on resistor to turn on the 5v relay, basically all we did is added the relay coil into the circuit by turning on the relay via transistors.
OK, put D826 back in place, I do not want to believe that we may have shorted coil in the 5V relay, every thing still in place but now we will remove the drive signal to Q8311 by removing R8310 (PAGE 2), or short out D8311 with a jumper.

[MEB]

Re: Toshiba 42HL196 - Clicking relay, Power Board

OK, I removed R8310 and the relay is not clicking any more, but the 5V1 to Gnd is still fluctuating.

[MEB]

Re: Toshiba 42HL196 - Clicking relay, Power Board

OH sorry, I didn't put D826 back, I'll be right back.

[budm]

Re: Toshiba 42HL196 - Clicking relay, Power Board

OK, I look at page 6, the Voltage (22V) for feeding the PFC is also used for running IC Q860 (STR-Z4479), so put a jumper R8712 and see what happen.

[MEB]

Re: Toshiba 42HL196 - Clicking relay, Power Board

Shorting R8712 doesn't stop 5V from fluctuating.

[budm]

Re: Toshiba 42HL196 - Clicking relay, Power Board

I just do not know what else is causing the 5V to fluctuate like that, if you take away the force on resistors with 10 Ohms load connected and it behave fine, you also already replace the start up caps C845, 8403.
Can you remove the force on resistors again to see if the fluctuation stops? I must be over looking something in the diagram some where.

[MEB]

Re: Toshiba 42HL196 - Clicking relay, Power Board

I removed the force on resistors and am reading 0 VDC at 5V1 and Gnd. Sorry I can not assist much.

[budm]

Re: Toshiba 42HL196 - Clicking relay, Power Board

I removed the force on resistors and am reading 0 VDC at 5V1 and Gnd. Sorry I can not assist much.

So it went dead again like last night and then some how you got it running again. Something is intermittent some where on the board.

[MEB]

Re: Toshiba 42HL196 - Clicking relay, Power Board

Hey bud, we gave it a good try. I will play around and hope to get back to you tomorrow. Thanks so much.

[budm]

Re: Toshiba 42HL196 - Clicking relay, Power Board

No problem, it is a tough one.