XT clone PSU puts 9.6v on 12v rail and -8.1 on -12v

[dhau]

Hello friends! I have this XT clone power supply, it's in really rough shape with lots of rust on metal parts. I cleaned it up pretty good, also removed all the dust and tried it out.

It puts out solid 5.1v on 5v rail and -5.1v on -5v rail. But it only puts out 9.6v on 12v rail and -8.1v on -12 rail.

I assume that's not good if I plan to use 5.25", 360KB DS/DD floppy drives, but probably fine if I use 3.5" drive as 720K DS/DD.

Did anyone see something like this happen? Should I recap it? Replace voltage regulators for 12v and -12v rails?

Thank you for your help!

 

[dorje]

Hi from France,

I read the same thing on my Amstrad PC 2086 PSU. The PC works fine, with quite clean +/-12V and +/-5V when the PC is running. It seems the PSU needs to be "loaded" to deliver nominal voltages.

Can anyone confirm ?

I'm no expert on PSU, so I'm not going to replace this noisy PSU with a modern-ish, silent one for now.

 

[whaka]

that's what i was going to suggest too.
some PSU need some load to regulate properly between 5 and 12.
try with motherboard + some hard drive, and see what happen on the 12V side

 

[dhau]

Thank you! I will try it out. I think I only need 12v for 5.25" floppy drives. I'll create a test floppy on a known good system and use it on this system to see if floppy drive works fine and keeps 300 rpm.

 

[dhau]

dorje and whaka - thank you very much for encouraging me! I connected this power supply to motherboard and put some load on +12v, and now it shows +11.98, very very nice! I no longer have concerns about floppy drives not having enough voltage to work with.