30V 5A power supply problem

[Pman]

I've got a power supply that was working great until all of a sudden it wasnt. I get a voltage reading and it will adjust but theres no Amps. From what I can tell it only has the one fuse at the powere input plug and of course that is fine. Can't see any visual cues as to what happened. It's just a cheapo unit YH-305D and worked fine for about 2.5 years. Any ideas?

Do have a common 30V 10A unit coming by the end of the week but it would be nice to see if there's a few simple checks I could do on the current one.

Thanks

 

[diachi]

Is it one of these?

If so - you don't happen to have the current turned all the way down do you?

Try giving the current pot a wiggle even if you don't, maybe the pot is faulty?

 

[Pman]

Yeah, that's the one.
I just looked it over again and found the simple issue with a wire.
So, there's good news, bad news and good news.
I found the issue and fixed it +
I ordered a new one since this one died -
I ordered a new one with 10A instead of 5A +++
Yay for me

Another cheapo but they work just fine for what we do with them. DCP3010D 30V 10A:

$71
http://www.ebay.com/itm/391321591608?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Same measurements as my other one so I'll just stack them. Always nice to have a back up so I'm not complaining.

 

[Benm]

These things are very good value for money.

One thing to be very careful with is directly driving laser diodes from them: I've seen som cases of such power supplies delivering a nasty output peak when switched on, possibly enough to kill a laser diode.

I'm not sure all of them share this issue though, but have a look on a scope before you attempt anything like that.

 

[Cyparagon]

These things are very good value for money.

I've worked with quite a few power supplies in my time, and I disagree. The thermal design is very poor (often running the pass bank at 120C or higher), the regulation is adequate at best, the main storage cap is usually under-rated, and the spikes at turn-on are usually horrendous. Several of them have broken for me. I can replace NPNs and beef up the cooling without much of an issue, but most people can't. I wouldn't recommend running those chinese linears at more than 60% their claimed max output current. At least not longer than a minute.

You can get used name-brand supplies for cheaper, and with more features.

 

[Benm]

You kinda get what you pay for really. Those cheap supplies are okay for occasional use.

A proper brand power supply like Tek or Rigol will set you back 500 euro's retail here for a 30V/5A model, though the 10A ones aren't much more expensive. Those will reliably deliver full current at any voltage 24/7 for years.

I guess there are some 'in between' brands like Voltcraft that are about double the price of the chinese ones, but with less messy start up peaks and more reliable components. It's hard to tell which are actually good quality unless you get to take them apart before purchase though

 

[Pman]

When I was looking for one all the ones I saw cheap were analog or the price with shipping was high or the connections were on the back.
I'm not doubting that the spikes are probably really bad at turn on but I have never blown a diode that way. Maybe I've just been lucky with mine but it has served me well. The one thing I don't like about the 10A one is there is no low range but then again I haven't used it yet except for messing with a Phlatlight. Doubt I'm going to need that accuracy anyways past 5A.
If the 5A one goes on me I'll ask Cyp first before acting on it.

 

[Benm]

Some people prefer analog meters, and sometimes they actually are quite useful if you want to see what's happening time-wise.

Especially for the current range it would be nice to have a switch for the range. Some power supplies have such a feature, but those usually aren't the cheap ones.