Most of what's on ebay seems to be low-quality chinese crap.
I have a Wavecom PS-3005D (Korad rebrand) SMPSU
Pretty happy with this for the price.
Did a quick scope of the unloaded power supply at the output set to 9V.
20M filter on
Linear is the only way to go in my view. The Ramco auction was a great shout, seen some great power supplies on there and hoping to win an Metrix AX503.
Linear is the only way to go in my view. The Ramco auction was a great shout, seen some great power supplies on there and hoping to win an Metrix AX503.
Linear is the only way to go in my view. The Ramco auction was a great shout, seen some great power supplies on there and hoping to win an Metrix AX503.That Metrix AX503 doesn't look very compelling to me. Voltage is shown with 1 decimal only. That is pretty much useless for electronics work.
At least this isn't a switching PSU.
I Strongly recommend against a switching power supply for doing electronics development because of the noise they can/will inject into your measurements. Don't get me wrong here; switching PSUs are great for delivering lots of power but not for use as a primary bench supply while making (sensitive) measurements.
At least this isn't a switching PSU.
I Strongly recommend against a switching power supply for doing electronics development because of the noise they can/will inject into your measurements. Don't get me wrong here; switching PSUs are great for delivering lots of power but not for use as a primary bench supply while making (sensitive) measurements.
Yes, it has very low noise, much better than very good SMPS. But you can catch some rare small pulses, see my picture above. These pulses are always present on the output even when output is OFF. It disappears when you power off PSU. I didn't find this noise on the spectrum, but you can catch it with oscilloscope. I suspect it comes from the dynamic indication of 7-segment LED.
Hi all, sorry if this is the wrong place,
I'm wanting a bench power supply for xmas. Ideally I'd like dual channel, up to 30V, up to 5A and linear. I've scoured ebay for second hand ones and it seems to be very thin on the ground. Budget is quite low, I'd like to keep it under £100 if possible. And I'm in the UK. Can anyone shed any light on my search? Most of what's on ebay seems to be low-quality chinese crap.
Thanks.
Have you done your measurement with any load on the output ? I suspect it could be very high impedance noise. Still not perfect, but it's likely your lab has electrical noise from other things.
In addition if the oscillations are 34MHz, they should be easy to filter out by adding a small LC filter on the line.
But I wonder if it is not oscillation or ringing in your probing setup.
Linear is the only way to go in my view. The Ramco auction was a great shout, seen some great power supplies on there and hoping to win an Metrix AX503.That Metrix AX503 doesn't look very compelling to me. Voltage is shown with 1 decimal only. That is pretty much useless for electronics work.
I wouldn't say that... many people just need a stable 5V or 12V with some intermediates in between, sometimes.
I typically pay between $10 and $20 for older working HP supplies. If you want one with digital displays, expect to pay considerably more but they won't work any better than an old linear supply with analog meters.
I have HP supplies from the 1960s that still work fine. One of the nice thing about the HP supplies is that they used GOOD capacitors and I've never seen a cap fail in one.
I typically pay between $10 and $20 for older working HP supplies. If you want one with digital displays, expect to pay considerably more but they won't work any better than an old linear supply with analog meters.I prefer digital meters. With analog meters I usually pull out a DMM to check the voltage. It might be worth checking out how accurate the meters on the Korad supply are. Recently I bought a bunch of Gophert PSUs (these are switching ones) from Aliexpress but their meters are shockingly accurate. Especially given the price.QuoteI have HP supplies from the 1960s that still work fine. One of the nice thing about the HP supplies is that they used GOOD capacitors and I've never seen a cap fail in one.I'd check the wiring in those. Especially when wires are soldered into boards directly. Over the years I have owned several older HP power supplies and in some I could pull the wires from the boards. Two of them needed replacing the electrolytics. In other words YMMV and I wouldn't recommend someone buying such old supplies.