Be aware: Yihua YH-305D bench PSU

[ablacon64]

I think I'll build one. Look what I've found, it seems very good and cheap to build:

[T4P]

well ... LM338 ...
that what makes it cheap and easy but certainly no good for a bench PSU, not even competitious with a OHL PSU
And also no current limiting either unless you make your own loop

[M. András]

the ammeter is in the wrong place too you could try look up some op amp datasheet these usually have a psu shematic if you want 8-10A look at the TI/BB opa 549

[AndyC_772]

I think I'll build one. Look what I've found, it seems very good and cheap to build:

That design might work, but I'd be seriously concerned about how hot it'll get. Draw a lot of current from it at a low voltage and those power transistors will get very, very hot indeed.

Example: if you draw the full 10A at 5V, then they'll be dropping 15V @ 10A = 150W of heat between them, 75W each. That's the equivalent of a couple of good soldering irons' worth per transistor, so that heat sink had better be very effective indeed. A fan wouldn't do any harm either.

[T4P]

And the heatsink would need to be at least 0.5C/W which is pretty HUGEEE

[saturation]

PSU should deliver clean power, and since the test unit doesn't it fails its fundamental purpose.

Its worth modding or repairing an Agilent or other name brand industrial supply, because likely the fault was due to abuse or a common wear-tear element: power capacitors.  But in cheaply made units, parts that haven't failed yet, may fail later on, leading to endless repair and wasted time and money.  Its a poor risk.

If you're in Canada, check out A1 electronics in Toronto.  At least you can return it if the units performance isn't good.

I just recently lost an eBay bid for an unbranded model exactly like the 305D, guess I was lucky after all :-)

The bid is now at 10$ + 30$ shipping. Even knowing the faults, would it be worthwhile? I'm really a hobbyist on a tight budget and between the JTag probes, soldering stations etc I have to be frugal.

Would a DIY solution be economical? or a kit?

thanks!

[ablacon64]

the ammeter is in the wrong place too

Why? I don't understand, it's a DC ammeter with an internal shunt, see (sorry, in portuguese DC is "CC"): http://www.ebay.com/itm/DC-0-10A-Analog-Ampmeter-Ammeter-Current-Panel-Shunt-/120782824832?pt=LH_DefaultDomain_0&hash=item1c1f37a580

[tom66]

The sad thing is, something like startup response costs nearly nothing to improve. Maybe a cap for the voltage reference to soft-start it, for example.

[M. András]

the ammeter is in the wrong place too

Why? I don't understand, it's a DC ammeter with an internal shunt, see (sorry, in portuguese DC is "CC"): http://www.ebay.com/itm/DC-0-10A-Analog-Ampmeter-Ammeter-Current-Panel-Shunt-/120782824832?pt=LH_DefaultDomain_0&hash=item1c1f37a580

cos on that place it measures the whole circuit's current not the output current

[ablacon64]

cos on that place it measures the whole circuit's current not the output current

Nice! I wasn't aware of that, thanks a lot! I'll put it before the voltmeter, is it ok?

[ablacon64]

Example: if you draw the full 10A at 5V, then they'll be dropping 15V @ 10A = 150W of heat between them, 75W each. That's the equivalent of a couple of good soldering irons' worth per transistor, so that heat sink had better be very effective indeed. A fan wouldn't do any harm either.

Do you think that adding one more TIP147 (or maybe two) would solve this issue?

[AndyC_772]

It won't really solve anything - the same amount of heat will still be generated, and will still have to be dissipated somehow, it'll just be spread amongst a couple more devices. The finished product will end up being 20% electronic parts and 80% heatsink. I hope you live somewhere that has a generally cold climate!

How much current do you actually need? This supply might be able to deliver a 10A surge quite happily, but it's really not a good design for a supply which might be required to deliver that sort of current continuously.

[ablacon64]

It won't really solve anything - the same amount of heat will still be generated, and will still have to be dissipated somehow, it'll just be spread amongst a couple more devices. The finished product will end up being 20% electronic parts and 80% heatsink. I hope you live somewhere that has a generally cold climate!

How much current do you actually need? This supply might be able to deliver a 10A surge quite happily, but it's really not a good design for a supply which might be required to deliver that sort of current continuously.

Well, I was planning to put a big heatsink on each transistor. And I need 6A max, usually up to 4 or 5.

[Tinman98]

I do not know if Yihua and Arksen are just brand names or manufacturers, but they look virtually identical inside and out.  And I can attest to the poor design and build quality of the ARKSEN. Oh sure, it works basically as advertised. But the quality is far less than even my Mastech power supplies.  The old phrase, You get what you pay for, comes to mind.

There is one external and one internal difference that is very obvious.  The binding posts are trash.  Knob is plastic only with no metal threaded insert. The post itself has poor threads that look like they were cast, and the post isn't even round.  Very easy to cross-thread.  On the inside, the most obvious difference between Mastech and ARKSEN, et all, is the transformer.  Arksen uses the old, very heavy steel laminate core that has been used for a hundred years (literally).  Mastech uses the newer, lighter toroidal core.

As mentioned by the original poster, the heat sink for the pass transistors leaves a LOT to be desired.  I have the 10 amp model, and it only takes seconds at well less than 10 amps for the heat sink to get fairly hot.  I have not tried to run it for an extended period of time.  The fan is terrible noisy.  I am working now to replace it, if it is a 12V fan, but have not yet determined what it is.

The assembly is VERY sloppy, to the point of potentially being dangerous.  A bundle of wires, including high voltage AC wires goes through the heat sink hole in back with out any kind of protection.  There is a protection sleeve, but the assembler did not bother to place it in the hole, so it's just useless.  The small bypass cap across the output terminals had one bare wire almost touching (maybe it was and didn't know it) between the hot and the ground terminal.  Many of the wires are poorly routed.  Most wire connections to terminals are protected by heat shrink tubing.  But get this. The wires to the bridge rectifier block have heat shrink tubing placed on them, but the dufus doing the assembly forgot to heat shrink them!!

I did not try to do any turn-on tests as the original poster did on the Yihua.  However, my unit (a 3010D, 30 volt, 10 amp) would not reach 30 volts, only about 28 (both actually measured and as displayed).  It did provide slightly over 10 amps however.  As I don't expect to actually need 30 volts, it's not a big enough deal to return.

All in all, this PS would be a good entry level for a new experimenter, but I would buy another Mastech before I bought another one of these, no matter how cheap.  And it was quite a bit cheaper than my Mastech, which is only a 5A, 30V.  One other downside is, I was easily able to find a schematic diagram for the Mastech.  I have not yet found one for the ARKSEN.  I was looking when I found this site.

[philpem]

Oh crap. We use those things at work, I think they're Iso-Tech branded (so probably came from RS)... I had a prototype damaged the other week with one, no further problems once I swapped it out for one of our (even older!) Thurlby Thandar PSUs.

I think I'm going to be even more jealously protective of the old Thandar in future.

[suppersready]

I have a PS305D wich is identical but branded "LONG WEI", at power-on and power-off i have a very short high speed spike but no overshoot.

I have replaced the FAN because was very noisy, here is a page with a PWM Temperature controlled FAN mod designed by me and fitted into the power supply.

http://mytecblogg.blogspot.it/2013/12/alimentatore-da-laboratorio-ps305d.html
 

[jimh]

Just thought I'd post to this in case anyone was still interested. I recently purchased and received (7/9/14) a YH-305D supply, and I believe it is a relatively recently manufactured model. First thing I did upon receiving it is to open it up and check out the bad things I had read about in several postings. I am sure that the 'bads' probably did exist in earlier models but the one I have was fairly well cleaned up.  The soldering was not U.S. quality but it was respectable. Wiring passing through the notch in the heatsink was protected with a length of cable harness covering. Relatively confident in the craftmanship, I decided to put the cover back on and proceed to do an operational checkout. The voltage regulation and adjustment worked well, however, the current limiting does not work. My load resistor was able to pull a full 5 amps (with voltage staying in regulation), but I could not adjust a current limit. Because of the current limit malfunction I did not proceed to checkout load transient performance. Fortunately, I only paid $56.00 for the supply. I will investigate the current limit situation and re-post if I can find a solution.

[pyromaniac4382]

I have a Yihua YH-305D that I got about a year ago. I will take pictures of its construction. The last time I used it I was shorting out the supply to adjust the current limit at which point the Unit popped and sparked.  The unit still works (I think), but the fan never worked out of the box. I have a feeling it was supposed to be tripped by a thermal element on the heat sink. So of course I got out my heat gun and blasted the thermal element on the heat sink, and it would not trip the fan, so I cut and hard wired the fan to always be on by-passing the thermal element. I wouldn't know what a bad one looks like, but it doesn't look too bad inside. I paid about ~$60 shipped, it seems like it could be altered into a safer to use supply.

[saturation]

I think its very easy for whomever makes Yihua to clean up their act; the bad things about it were just quality control issues in assembly as well as possibly bad sources for parts; the supply acts like any linear supply of 1970s design.  In the end, for best thing for all these cheapo brand ?? Chinese supplies is to open them up and check assembly and parts, do a functional test [output stability, ripple, etc.,] and finally some form of "burn in" [ say pull 50% power over 24 hours and checking for overheating and output stability or more exotic ones if you have an e-load ] while the unit is under warranty.  If it fails the burn in, at least you can still return it.  You never know what you get from one production batch to the next, regardless of brand.

[alex27riva]

Hi, how can i fix this problem?

[saturation]

Since the volts reading is stable it suggests the output current is also stable but the meter is faulted, likely the IC itself in the module.

To confirm this, attach a good ammeter to the output and adjust the current.  You should see the good ammeter read linearly as you adjust up and down while the PSU ammeter reads all over the place.  Short circuit the output, and the CC LED should light, a final note that the current module is working by testing the short circuit protection.

If the above works, then its easiest to replace the ammeter module rather than repairing it.

Hi, how can i fix this problem?

[alex27riva]

This problem occurs only a few times, now no longer does

[saturation]

That good news, its likely a poor connection or solder joint in the amp module.  Chilling the unit could cause the problem to reoccur and warming it up can make it disappear.

This problem occurs only a few times, now no longer does

[LEDAero]

Hi, how can i fix this problem?

I think hitting it was the right thing to do. It's a universal fix...

[/sarc]

[laser411]

I've got one of these, I have a problem..... I dropped it at one point and broke the case. it still worked, but shortly after I had a problem where it would max the current out at 0 with the current limit light on no matter where the knob was turned (after a few minutes of operation). Now if wont put out anything at all. Shows current limited with 0.00 volts AND amps. Any idea what the problem could be?

Honestly not sure if it was from the drop or not. doesn't seem to be anything but broken plastic, I also ran it maxed out for 30 minutes one day trying to blow an automotive lightbulb (ended up cutting itself off for like 10 minutes) Drop was shortly after that >_<