Power supply beeps

[Stairmaster]

Hello everyone I have gained a HPZ820 and I am having problems here is what happens 

turned machine on worked for approx 10 ten mins then switched off on its own accord 

so I tried to restart and I got fans on full speed few seconds then 4 Beeps and Red light flashing

i have removed the power supply and plugged into mains, and the green light on power supply does this indicate power supply is Ok ?
if I can’t fix it just sell as parts not working

thank you 

[BeemerBiker]

LED and beep codes for your system

https://support.hp.com/us-en/product/hp-z820-workstation/5225041/document/ish_1997210-1528385-16

If ran for 10 minutes after first power up things may not be all that bad.

Typical motherboard is here

I would look at all the electrolytic capacitors for problems

example of what bad caps look like is here

[Prométhée]

hi

check but you have here, different manuals the given link, is quite generic
you have the manual for this series, and there are not the same indications, note that there are not only 4 beeps

first

HP Desktop PCs - Computer beeps

The red light blinks four times, and then two, short white light blinks (4 long red, 2 short white)

This condition indicates that the processor (CPU) might be overheating.

The red light blinks four times, and then three, short white light blinks (4 long red, 3 short white)

This condition indicates that the computer temperature is too high.

The red light blinks four times, and then four, short white light blinks (4 long red, 4 short white)

This condition indicates that the MXM graphics card temperature is too high.

 HP Z220 SFF, Z220 CMT, Z420, Z620, and Z820 Workstations Maintenance and Service Guide

Red Power LED blinks four times, once every second, followed by a two-second pause. Four
beeps

Power failure (powersupply is overloaded).

CAUTION: Internal components might be powered even when
the computer is off. To prevent damage, disconnect the
computer power cord before you remove a component.

. Open the access panel and ensure that all power
connections are secure on the system board.

Check if a device is causing the problem by removing all
attached devices (such as hard, diskette, or optical disk
drives, and expansion cards.) Power on the computer. If the
system enters the POST, power off and replace one device
at a time; repeat this procedure until failure occurs. Replace
the device that is causing the failure. Continue adding
devices one at a time to ensure all devices are functioning
properly