RCA L37wd12

[dhack61]

Having a problem with voltage drop going from SMPS 1W to the Scaler board. Unplugged from the scaler I have 5.3v standby on the SMPS 1w going out. As soon as I plug the scaler back up the standby voltage drops to 3.6.
Any Ideas?

Dhack

[budm]

Re: RCA L37wd12

Please post good clear pictures of the boards using attachment so we can see how all the boards are connected together.

[tom66]

Re: RCA L37wd12

Some of these newer low power TVs change the standby voltage to a lower voltage in standby to reduce the power dissipation in standby mode, to help meet Blue Angel/Energy Star requirements. Is there a control signal on the PSU that might indicate this?

[dhack61]

Re: RCA L37wd12

Here is a copy of the interconnect Dia from the service manual. Its marked L32wd12 but its the same for both sets.

The Voltage chart shows that 5.3v should be coming in to the scaler board.

Dhack

[tom66]

Re: RCA L37wd12

Can you get hold of a 10 ohm 5W resistor?

I do see a signal "PO" going to the 1W board. Can you post a picture of this 1W board?

[budm]

Re: RCA L37wd12

I see, it has the same setup as the 26" version that I worked on years ago, the PO is the power on signal to turn on the relay on the main inlet board which supply 120vac to the input of the SMPS board.

http://s807.photobucket.com/albums/y...RCA%20L26WD12/

This one had bad main board, the relay click but no other action happen, then 6 months later, the inverter boards went out. After repalceing boards, the TV is still runing for 3 years now.

[dhack61]

Re: RCA L37wd12

I see, it has the same setup as the 26" version that I worked on years ago, the PO is the power on signal to turn on the relay on the main inlet board which supply 120vac to the input of the SMPS board.

http://s807.photobucket.com/albums/y...RCA%20L26WD12/

This one had bad main board, the relay click but no other action happen, then 6 months later, the inverter boards went out. After repalceing boards, the TV is still runing for 3 years now.

That's pretty much the same set on smaller. I am not getting the click to start the 120V on the main SMPS. You said the main board was out. do you mean the Scaler board?

[dhack61]

Re: RCA L37wd12

Can you get hold of a 10 ohm 5W resistor?

I do see a signal "PO" going to the 1W board. Can you post a picture of this 1W board?

Don't have a camera charged but I do have the Schematic for the board. If you still need a picture let me know.

[tom66]

Re: RCA L37wd12

Doesn't look like the PSU adjusts voltage in standby, so it's either a main board loading down the PSU too much or a problem with the PSU.

Potential causes with PSU:
- CP616 main output cap 470u
- CP613 Vcc cap
- RP613 Vcc run-charge resistor and;
- DP617 diode
- DP601 relay diode (rare, unexpected but don't eliminate it - maybe it's shorting PSU when PO turns on...)

Potential problem with main board is a shorted or low resistance component.

If you can get that 10 ohm resistor the main board can be eliminated if the power supply drops under load. Troubleshooting PSUs is much easier than main boards.

[lazuras]

Re: RCA L37wd12

i have a L32WD12 the power supply looks similar to the one shown here . my question is im changing the capacitors on them i change the three larger ones but i donot or cannot read or understand what the smaller three are. hopefully it will work. right know my tv turns on red light but thats it then turns off. i here a click . then off . and sometimes when it turns on still a red light but flickers.