Hi all
I've got an Alpha Elettronica AL 626 S bench PSU, 5 + 15V 20A.
Upon turning it on, the amp needle slams to the max. When measuring the voltage with no load it looks correct but when I attach a car light bulb to it the voltage needle drops and the overcurrent and shutdown lamps light up randomly. The bulb never lights up.
It also does this for a while after I turn it off (it doesn't appear to discharge itself).
Does anyone know where I can get schematics for this? Any idea what could cause this behaviour? There are no smells, smoke or sparks otherwise. I have no idea about lab PSUs
Thanks!
they seems alive on the web, pop them an email
a schematic who could ressemble to your unit ...
normally theses have a simple design like many on the web IE: pyramid power supplies psk-21 etc ...
Ok, their customer support was nice and sent me the attached documents. Not sure if the "S" variants has major differences but I'll find out soon enough.
Where do I start measuring? What is a "simple design"? Are these all based on the same principle?
I got it apart so I can work on the PCB.
Thanks for any hints
If someone compared the PCB with the schematic you might have noticed that they have little in common, only the chunky PSU parts match it but I don't have any ICs on mine.
Anyway, I poked and prodded at some point it worked, so I thought it's a cold solder joint. After reflowing the solder joints on the PCB it went back to its previous behaviour.
So I poked and prodded outside of the PCB area and found out that there is some intermittent in the Amp meter movement.
I don't know what exactly it is, but when I push the plastic window it goes back to 0 and I can use the PSU. The light bulb now lights up.
Any ideas what could cause this? I'll probably take the Amp meter apart... is there anything I could substitute it with in case it breaks entirely?
I cleaned and deoxited the contacts / screw posts of the amp meter and now it doesn't seem to be intermittent anymore.
problem solved!