110 power, no circuit board lighting why is it not lighting?

Back - light problem. Check and replace damaged component/s at its back-light inverter board, or replace this board as card basis. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts. It will be best to replace the inverter board as card basis.
http://electro-medical.blogspot.com/
http://electronicshelponline.blogspot.com/
To some model sets; especially LED back-lighted types; the back-light inverter circuit will be part of the main power supply board [SMPS]. In such cases, the power supply board might need replacement. To some models sets, the back-light inverter and SMPS section circuit will be integrated at its main board itself. If so; the main board should be replaced. To some models of sets, all these section circuit will be integrated at its main board. If this is the case, you have to replace the main board.

Manuals and info here:
HP 110 014 Desktop PC ENERGY STAR How to

back to your original question. If I understand correctly you are asking how to change the power supply circuit board. The quick answer is you can't.. For safety reasons the power supply contains no user serviceable parts, including fuses. It must be replaced. The good news? they're not very expensive

Do you have any lights working on the front panel? If not most lower circuit boards have a small fuse on the circuit board. shut down ALL power before checking for the fuse.The lower board has both 115 volts as well as 12 volts. If the lights are working on the front panel then most likely the lower circuit board is faulty and will need to be replaced.

You said there was NO lights on the unit. The Dometic service manual says:

1. No operation - no panel lights: DC Volts

Fuse

Wiring

Upper Circuit Board

Lower Circuit Board

http://www.gasrefrigeration.net/dom_techdata/26121_2852SM.PDF

I would start with the DC volatage and track it back until you lose it. Most of the time it does end up being the lower circuit board though.

Check for voltaged at the solenoid valve. This will either be a 24 volt or 110 volt solenoid valve. Confirm power into the unit 110 volts. If you have power into the unit and no voltaged at the solenoid valve on a call for humidification at the humidistat than the circuit board or the step down transfgormer has failed.. If you do have voltage at the solenid valve than the valve has failed.

Check the 110 volt wire for flaws. Take a volt meter and check the recep that the fridge plugs into for power, should be 110 volts or so. +/- 10%. If you have power at the recep problem is in the fridge chord or circuit board fuse or circuit board. Also check the 110 volt breaker in the coach at the service panel.

You may only be receiving 110 volts, instead of the 240 volts needed to operate. (Thus, only the light coming on)

Did you reset the dryer circuit breakers?
Are you receiving 240v to the plug?

-Chad

Solved by resoldering some solder joints!!!!!!!
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Toshiba Model 57H81 Rear Projection TV - Purchased 11-09-2001

Problem: Toshiba 57H81 Flashing Red Power Light, No Picture/Sound, Blown Fuses F850 + F852

Symptoms January, 2009:

• Upon turning on set I got flashing red power light and nothing else.
• Removing plug for one minute and plugging in results in:
• Audible click, steady red power light for 2 seconds then slow flashing red light
• Pushing power button results in steady red for about 2 seconds then slow flashing red light, no other set activity
• Removing power cord for several hours and plugging back in made no change
• Audible click, steady red for about 2 seconds then slow flashing red light
• Possible related note: Over past several months occasionally the entire screen would flicker momentarily and at other times be problem free for weeks.
• Fuses F850 and F852 found blown

Repairs Made:

• PD0074 DEF/CON Power Board
• There are two main power supply capacitors in this set. They are C-809 and C-810. One their negative lead on the printed circuit board re-soldered leads and nearby contacts. I’m told that because the factory left out a printed circuit board eyelet, the connection will come loose over time. When I called Toshiba customer service they said there was a known solder joint problem causing blinking red light.
• Replaced blown fuses F850 and F852.
• I actually installed a fuse panel on the inside of the cabinet and routed the fuse connections here instead of ordering the special fuses and replacing them on the circuit board.
• Had to use a 5 Amp SLO-BLOW for F850. Fast blow does not survive power up. Get the red blinking light.
• Used a fast blow 2 Amp for F852.
• PD0073 SIGNAL Board
• Re-soldered Q751 + Q752 STK392-110 Convergence Amps
• Re-soldered adjacent pads that looks suspicious

Total Cost to Repair about $10

• Twelve hours of my time over three days to research issue, disassemble set, make repairs, add fuse panel.
• Already owned Service Manual and Circuit diagrams from a different 2004 repair.
• Less than ten dollars at Radio Shack for fuses and fuse panel. Already had wires, etc.
• Some solder. Already owned de-soldering tools, etc.
• Visited both local authorized Toshiba factory service repair facilities. One said repair would have to include replacing Q751 + Q752 STK392-110 Convergence Amps with ST392-180, and realigning set for a total of $500+ and it would be more if they had to order a power board. NO THANK YOU! Other shop said $65 for site visit and $30 to make an estimate that could be applied to repair.