Author Topic: Be aware: Yihua YH-305D bench PSU  (Read 16661 times)

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Offline saturation

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Be aware: Yihua YH-305D bench PSU
« on: March 22, 2012, 06:19:57 AM »
I've been running into this Instek, Mastech etc., look a like during eBay or google searches on bench power supplies.  Its fairly prolific and some vendors are selling them like hotcakes.

Comparing Mastech and Yihua model appearances:




For example, both with the Yihua name and name removed, but containing the same model number.  Scores are sold, and one vendor has > 800 stocked:

http://www.ebay.com/itm/290647013768?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
http://www.ebay.com/itm/140675103345?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

However, a user posted this youtube video on its simple turn-on response of a new Yihua versus his older Mastech PSU:

To ebay seller xcceries regarding the YH-305D



Key frame grabs:

Mastech:


Yihua:



« Last Edit: March 22, 2012, 06:35:22 AM by saturation »
Best Wishes,


Saturation

Offline ron

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Re: Be aware: Yihua YH-305D bench PSU
« Reply #1 on: March 22, 2012, 07:03:07 AM »
schematic of a 305D ... any mod suggestions?
« Last Edit: March 22, 2012, 03:32:01 PM by ron »

Offline ron

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Re: Be aware: Yihua YH-305D bench PSU
« Reply #2 on: March 22, 2012, 07:59:40 AM »
I just did a quick check on a 305D.  Driving a ~6 ohm ww at 2.5 volt / .5 amp, I get a .5volt overshoot and ~.008 volt / 60hz ripple.

Offline Spawn

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Re: Be aware: Yihua YH-305D bench PSU
« Reply #3 on: March 22, 2012, 02:41:55 PM »
Lol nice to see that, I got a Yihua PS-3010D

It’s a 10A version without Low and High Amps limitation, I wrote something about it in another topic while I was testing the fan noise of my scope.

The power supply came out the box with burned plus banana plug inserts, they used some crappy 3A versions so I changed that to 16A versions, and the fan makes too much noise (it is always on).
There is a huge capacitor dangling around in the housing which they try to mount to the bottom with a tie-rap mount, but that was also loose of course.
Wiring inside is crap, there are 4 output transistors mounted inside the housing on a 2mm aluminum piece used as heat sink but it is not even close to one.

I just checked my phone there was some pictures of it which I took for my friend, I will post that below, also a movie with output noise on a scope.

I use the power supply for high current automotive lambs and other automotive things to test them out, so it is good enough for couple minutes using for me on not so fragile things.

But to be honest, I wouldn’t recommend this power supply to anyone who is doing some fine electronics projects.

I was going to review this power supply but I really need a bigger bench, I don’t have any room on my bench so I am heavily busy to make a new bench.

Anyways here are the pictures:





Sorry I guess my phone cam needs better focus  ::)



And I was testing its DC output noise here, you also hear the fan sound after switching:
30V - 10A DC bench power supply output and sound noise.


Offline T4P

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Re: Be aware: Yihua YH-305D bench PSU
« Reply #4 on: March 22, 2012, 05:10:12 PM »
Do they use preregulator switching ?
Or is it truly linear and uses multiple taps relay switching ?
http://the4thpin.comeze.com <-- Rants and Reviews! sorry my english  :palm:

Offline Spawn

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Re: Be aware: Yihua YH-305D bench PSU
« Reply #5 on: March 22, 2012, 11:34:59 PM »
My model uses relays, switching at 8v, 16v and 24v

Offline T4P

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Re: Be aware: Yihua YH-305D bench PSU
« Reply #6 on: March 23, 2012, 02:02:09 AM »
http://the4thpin.comeze.com <-- Rants and Reviews! sorry my english  :palm:

Offline saturation

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Re: Be aware: Yihua YH-305D bench PSU
« Reply #7 on: March 30, 2012, 07:53:27 AM »
Yet another bad review, this time more suggestive of an intrinsic design fault or use of very inferior parts:

http://www.amazon.com/Precision-Variable-Adjustable-Power-Supply/dp/B005DHZVJK
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Saturation

Offline Salas

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Re: Be aware: Yihua YH-305D bench PSU
« Reply #8 on: May 25, 2012, 04:49:31 AM »
Looks like Yihua and Mastech have same origin but circuit differences then. No problems with my Mastech branded dual also.

Offline saturation

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Re: Be aware: Yihua YH-305D bench PSU
« Reply #9 on: May 25, 2012, 05:35:29 AM »
I'm happy for you.  I guess you can say Yihua and Mastech both originate from China, but there quality is far different.  Your unit looks well made, by what I can see of the assembly, and most Mastech's I read about work as expected, and few if not any complaints.  But I can't be sure that the brand name Matech is made by same company if you buy it in the US, Greece or other places in the world.  So caveat emptor.

If you look at Spawn's Yihua photo here:

http://www.eevblog.com/forum/product-reviews-photos-and-discussion/beware-yihua-yh-305d-bench-psu/msg99235/#msg99235

What can be seen at the top PCB looks rough, the power resistors that are dangling in the rear heatsink, and its odd to have a floating capacitor that is just zip tied, see middle photo.
Best Wishes,


Saturation

Offline Spawn

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Re: Be aware: Yihua YH-305D bench PSU
« Reply #10 on: May 25, 2012, 06:02:55 AM »
Saturation is right there, yours look a lot better build than mine, like I mention mine came with melted plus connector, since I use it only for rough tests like automotive lambs  and so on, it doesn’t matter, I got couple other supplies for more delicate work.

Offline Salas

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Re: Be aware: Yihua YH-305D bench PSU
« Reply #11 on: May 25, 2012, 06:20:53 AM »
The NTC thing I added it myself primary side by the way. Because it was 2 out of five times tripping my 10A breaker line when its massive toroid Tx was building up field at start up.

Offline cliffyk

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Re: Be aware: Yihua YH-305D bench PSU
« Reply #12 on: May 25, 2012, 08:05:50 AM »
While it is obvious that the loaded start-up and regulations characteristics of the MasTech supply are superior to those of the Yihua unit, it would never occur to me to start-up either supply with a load connected--especially if said load were a an established device or project under development--BTW the Mastech's ability in that regard are impressive.

With regard to MasTech bench supplies however, I have a dead HY-3010E that will will give to anyone willing to pay the packing and shipping costs.  I bought it several years ago and was never impressed with it's quality, i worked for a couple years and then the smoke came out--MasTech was of no help whatsoever, they sent me a schematic that is different from the version I have and made it clear that no replacement parts or modules were available.  It is a switching type supply and I believe the transformer in the control supply is shorted.

I also have two Leader bench supplies, a 7110-3D 110V 3A and a 718-20D 18V 20A.  They look very similar to the MasTech instruments, which I believe to be at least cosmetically clones of the Leader units, and are 10-15 years old and have never missed a beat.  They are digitally controlled analog supplies whose only deficit is their weight.

The "yee-haw" supplies would appear to be cosmetic clones of the MasTech devices...
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Offline mAJORD

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Re: Be aware: Yihua YH-305D bench PSU
« Reply #13 on: May 25, 2012, 10:27:52 AM »
While it is obvious that the loaded start-up and regulations characteristics of the MasTech supply are superior to those of the Yihua unit, it would never occur to me to start-up either supply with a load connected--especially if said load were a an established device or project under development--BTW the Mastech's ability in that regard are impressive.

With regard to MasTech bench supplies however, I have a dead HY-3010E that will will give to anyone willing to pay the packing and shipping costs.  I bought it several years ago and was never impressed with it's quality, i worked for a couple years and then the smoke came out--MasTech was of no help whatsoever, they sent me a schematic that is different from the version I have and made it clear that no replacement parts or modules were available.  It is a switching type supply and I believe the transformer in the control supply is shorted.

I also have two Leader bench supplies, a 7110-3D 110V 3A and a 718-20D 18V 20A.  They look very similar to the MasTech instruments, which I believe to be at least cosmetically clones of the Leader units, and are 10-15 years old and have never missed a beat.  They are digitally controlled analog supplies whose only deficit is their weight.

The "yee-haw" supplies would appear to be cosmetic clones of the MasTech devices...

Actually, all these units (Yihua and co, above mastech, Leader) are  aesthetic copies, or rebadged Goodwill (now GW Instek) units.

The classic design dates back god knows how long, and originally had analogue readouts. You can still buy this version new (GPS-3030). I think nearly every electronics bench I've seen has has one of these. They're very recognisable, probably why everyone copies them.

back to the topic though, I've got some pictures at home of a really cheap BEST supply.. another Yihua under the skin I believe.

quite amusing, It arrived with the front PCB smashed off, and after I decided to load test it at 1.5A (Rated 2A) for a while, the main transformer burnt out (primary short)

I shall post pic's later
« Last Edit: May 25, 2012, 10:32:12 AM by mAJORD »

Offline cliffyk

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Re: Be aware: Yihua YH-305D bench PSU
« Reply #14 on: May 25, 2012, 10:42:24 AM »
I have to disagree, to the extent that the older, "heavy" (40 lbs), Leader supplies like those I have--made in 1994 and 1995--share nothing with the newer GW/Instek, MasTech, and whatever clones.  They were made well before Leader had begun acquiring machines from GoodWill...
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