Replacing power supply is simple and can be done anywhere. Here’s a IBM link for replaceing the power supply.
You can Google Model 820 Power Supply and find a third party where you can buy the part.
820’s are releatively simple to change the pwr supply. You may have multiple power supplies in yours
for redundancy as it still pwrs up but clicks, (usualy a sign that a switched mode power supply is defective) To check: If more than one power cord is installed then you have more than one supply.
To isolate the failing one powerdown then remove the power cords one at time and try to power up
if it comes up it was not that supply, remove the failing one using the instruction below. This can normally be done concurrently but I don’t reccomend it for some one who is not experienced.
Power down and remove all power cords, undo the 2 x knurled and slotted screws on the RH side rear cover (view from the rear the LH side) slide the cover about 1/2″ to the rear and remove.
Next grab the handle opf the failing supply and lift it to horizontal, remove the drive.
Reverse the procedure to replace.
Note if you are using the machine at home my guess is that redundancy is not critical so you could just remove the failing supply and not bother replacing it
E-mail me if you have further questions
820’s are easy to work on, IBM has docs for the process – get a copy of hardware maint from site.
I have changed the power supply and I would recommend changing both if you do – I ordered one and these are not avail at to many places – so when the power supply was added and powered up the other one failed. Vendor sent 2 new ones – I swapped after.
No issues, mostly hard drive failures.
I talked to vendor and he agreed that we neede to swap out both.
Almost like changing tubes in a power amp (Push<>Pull)