DC Power Supply Question

[Gooch]

Hi everyone
I am new here been watching Dave's video's and reading posts I play around with diy audio build a few things now and want to up my game and learn more about electronic. I was given a Lambda LP412A-FM power supply I know it's kinda dated piece of equipment it seems to work ok. So  my question is I was testing a zener diode I set my voltage to 20V and about 10mA current I put a 1k load resistor in line on the negative rail under load it's dropping about 6 volts is this normal.

Thanks
Dave

[alm]

Lambda made (and makes) excellent power supplies, so I see nothing wrong with starting with this power supply. Apart from obvious limitations like no computer control and only a single channel this power supply should perform very similar to new power supplies, and is better made than the cheap power supplies that go under various names often sold new on eBay. If you didn't get a manual, you can get a PDF copy at ArtekManuals, but I don't really see a reason to need this manual unless you need to repair it or want to use the remote programming / sensing connections at the back.

According to Ohm's law, putting 20 V across a 1 kohm resistor would cause 20 ma current to flow. You don't mention the zener voltage, but from your description I assume it would be about 5V, so the same argument would still apply (15V across 1 kohm would mean 15 mA would flow, more than the 10 mA limit). Since you limit the current to 10 mA, the power supply will reduce the voltage to keep the current under 10 mA. Increase the current limit and you should see that the voltage remains stable under load.

[Gooch]

Thanks for the reply alm

Thats good to know about the power supply the zener's where 9v and one 6v I build this preamp kit a few years ago and just couldn't get it to work I got tiered of pulling parts of the PCB hoping it would work so I put it a side. Now I have decided to give it ago again so I been trying to really wrap my head around it and under stand it I am not an EE this is also to only kit I built where I didn't source the parts myself so I might have had a bad part from the beginning thanks again.

Regards
Dave