Pavilion a1129n will not start

"I have the ability to repair the power supply, with some guidance. It's no different than a power supply in a stereo system, or, realistically, nearly every electronic device that uses a transformer to reduce voltage. I'm not afraid to take it apart and check the components. I'm just looking for smart place to start the diagnosis."
PSU on any PC desktop made can be bench tested.
easy or more complete with tools.
many parts in any PSU have custom contract parts (a secret)
SO ABILITY IS SUPER LIMITED ON PSU. MAKER NOT MODEL TOLD OF PSU./
The Psu has fuse deep inside, some are hidden in the transformer, too. if blow out now the F1 fuse the fuse blows 99%^of the time replaced due to other parts are shorted,most you can not buy
but caps yes and easy.
the fan dead tells you the +12vdc rail is dead (at least)
here is the bench test (forget PC for now)_
jumper test and more.

https://pcdied.com/PSU/power.html#the_jump_start_magic

the PSU needs a good cord AC. not dog chewed.
it needs AC power not dead. at the wall
No funky power strips .
yes monte said check wall power, I use hair dryer,wifes
1500 watts is great test for any wall jack AC 15/20amps /
and first the old silly 115/230 switch not seen today.

this PSU is SMPS unlike cheap home stereo gear.
as seen here great examples

https://pcdied.com/PSU/schematics/html/image_1.html

your day1 new OOBE PSU was 300watt
hp # 5188-0129


here it is day1 new, shown at hp partsurfer.com



avoid electric shocks seen here.

https://pcdied.com/PSU/schematics/images/bridge-hv-ouch.jpg

if you are not getting any lights on the laptop when you turn on,,try checking the fuse in your plug or get your power supply checked out and also your battery.

Power getting to the computer/Power Supply?
Yeah.

Power Supply good? -> NO

A) IF ALL of the LED lights were on at once, they would use less than 1 Watt of power.

B) EACH fan uses 2 to 3 Watts of power.

C) A typical Processor can use from 51 to 125 Watts of power.
Just depends on what Processor it is.

HP Pavilion a810n Desktop PC?
Uses an AMD Athlon 64 3300+ processor,
(Operates Up To a frequency rate of 2.4GHz)

http://h10025.www1.hp.com/ewfrf/wc/document?lc=en&dlc=en&cc=us&docname=c00280647

http://en.wikipedia.org/wiki/List_of_amd_athlon_64_microprocessors#.22Newcastle.22_.28CG.2C_130_nm.29

Can use up to 89 Watts of power.

Your Power Supply doesn't even have enough power to spin fans, much less start the Processor.

Want to test the Power Supply? Have a multimeter?
No? Have a power supply you can borrow for a test unit?
KNOWN to be good, and Compatible?

For additional questions please post in a Comment.
Regards,
joecoolvette

Sounds like your power supply has gone bad. You will need to get a new power supply. They can be found online, or in most electronic retailers.

you need to replace the power supply -- there is no fuse

are you certain its the power supply ? how do you know its not more than just the power suplly unit, such as bad motherboard, or hard dis\k drive as well as power supply

try removing the front panel make sure the button isnt clogged with dust or disconected failing that it may well be your power supply internal fuse which can be repaird but a trick job if youare not very good with a soldering iron you may get a replacement one on ebay.

Power battery store supply good HP laptop ac adapter of 90W/100W.

try to check the wall power outlet if have power output, if have ,try to check the avr if the led lights up if not try to check the fuse of avr maybe its busted, if not, try to check the power cable that used to plug to system unit if have power output use multitester and if have, replace your system power supply.

This is a case where something that is getting switched on during start-up is causing the power supply to fail... probably due to a short. How ever I believe the short is in the power supply

This is an older HP model ( I have a 530N) with teh same problem. I bought a new power supply and installed it.

Your power supply is bad--you will need to replace. I suggest looking at tigerdiect for a replacement.