Solved:Alpha Elettronica AL 626 S bench PSU: no current - looking for schematics

[agent_power]

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!

[coromonadalix]

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 ...

[agent_power]

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

[agent_power]

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?

[agent_power]

I cleaned and deoxited the contacts / screw posts of the amp meter and now it doesn't seem to be intermittent anymore.

problem solved!