New power supply doesn't power on

Discussion in 'General Electronics Chat' started by ke5nnt, Dec 18, 2011.

  1. ke5nnt

    Thread Starter Active Member

    Mar 1, 2009
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    Hey guys,

    I had a thread previously from a week or two ago asking about suggestions for power supplies. Someone had recommended the Mastech HY3003F-3, I liked what I saw, so I bought one off of ebay. The listing stated the condition was "New (other)" and stated that it was bought new and never used, and that it had just been sitting in an air conditioned office for 6 months. It was opened and missing the original packaging, so I thought, okay, I can live with that.

    Well the thing gets here and I open it up. It looks like it's been dropped. There's a scar on the top corner of the front faceplate, and part of the faceplate on the side where it wraps around is cracked. Also, the power cord has a big slash in it that looks like it lost in a fight against a razor blade, which causes the power cord to not even fit into the receptacle. I had another power cord of the same type sitting around, so I used that and plugged it in and pushed the power button...nothing. No clicks (other than the button) no indication of power being received at all. I tested the fuse and ensured that the unit was getting voltage from the wall outlet, both are fine.

    So here are my questions. I don't know really the first thing about fixing power supplies, but it's possible that with guidance from all of you, I might be able to just fix it and call it good, I can live with the scar and the crack as long as the unit works well.

    Has anyone ever had a bad deal on ebay and had to go through the buyer protection system? How did that go for you? The seller had stated in the listing that returns are accepted within 7 days and that the buyer pays shipping costs, but he also stated "guaranteed to be working upon arrival". I'm a little old-school perhaps in my thought process, but I paid for a "new" item, so I expect a new item. If that means that I have to send it back to the guy for a refund, then I want to be restored all of my costs, which include the cost of the item, the $40.00 I paid to have it shipped to me, and undoubtedly the $40.00 I'd have to pay to return it to the guy who sold it to me. The alternative is, he refunds me the cost of the unit alone (without the shipping) and I'm left with a brick to try and fix.

    Any thoughts on anything with this guys? Sorry about the length of the post (again).
     
  2. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    I'd contact the seller. What type of rating did the seller have? If the seller has sold a number of items and has a good rating the seller may want to keep that rating and refund no question.

    But with the obvious discrepancy between what was posted and what you got the seller was either lying or there was some kind of mix up on what was sent.
     
  3. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    If the photos do not match, and it doesn't work when it was stated it did, contact the seller first.

    Don't leave negative feedback right way, it'll make working it out harder.

    If he tries to blow you off, take it to eBay arbitration.
     
  4. ke5nnt

    Thread Starter Active Member

    Mar 1, 2009
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    I had sent an email to the guy before posting this thread. Waiting on a response. I guess I was more interested in ideas to get it fixed cause I'm bummed out it didn't work when it arrived.
     
  5. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    If you wanna have a whack at it, then post pictures first
     
  6. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    Amen, brother. I never buy anything on ebay unless I am prepared to have it show up in pieces as yours did. They pinch on shipping and then it gets damaged..... and if you are lucky, you get your purchase price refunded but you have to eat the return shipping costs.

    I never buy anything on ebay unless it's REALLY a bargain because of that.
     
  7. ke5nnt

    Thread Starter Active Member

    Mar 1, 2009
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    Ok, follow up to this story. The guy emailed me back and swears up and down that the power supply was 100% functional and undamaged upon leaving his office. I sent him pictures of the damage and he immediately refunded me FULL purchase price including the shipping costs, no questions asked... so I got super lucky there. He'll be taking up the insurance claim with the US Postal Service.

    So that brings me to this. I have a supply that looks relatively good, and has a nice clean inside, just doesn't turn on. I've been having a hard time finding a schematic online for this supply, which again, is a Mastech HY3003F-3. If I can get it working, that would be great, but I have no experience with fixing power supplies of any kind, though I've heard that fixing a linear supply is relatively easy as long as the transformer is in good shape.

    So let me know what you want pictures of, and if you guys want to help me try and get it working, I would be extremely grateful. If I get it working and it's matched with factory specs, I'll send the seller an email offering to pay a reduced price for the unit, or ship it back to him, or something.
     
  8. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    Glad to see that last paragraph. If you want to keep it you need to be fair to the seller.

    My guess he had 2 supplies to sell. One damaged and one working. He sent you the wrong one. I can see some of that damage caused bt shipping but the slash in the power cord? How was it packed?



    Mastech is a fairly well known company of inexpensive test equipment. You might want to contact them to see if a schematic is available.


     
  9. SgtWookie

    Expert

    Jul 17, 2007
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    I'll bet the packaging was not adequate.

    Inadequate packaging on something like that will make it look like it was dropped off a building when received. The USPS has trained gorillas play soccer with your packages while other employees cheer them on.

    Seriously though, if there are any sharp corners on an item, it needs to be VERY well padded, as if the item is dropped or falls during shipment, the sharp corner will cut like a knife through the packaging. The power cord was very likely a victim of a sharp edge + a fall. It doesn't take much when the weight of the entire instrument is stopped by one sharp edge; much like a meat cleaver.

    Since you basically have a free non-functional power supply now, might as well remove the cover (cord unplugged, of course) and have a look inside it.

    If you have a camera capable of creating .jpg images, its' time to put it to use.

    Start by looking at where the power cord plugs in; stress caused by dropping could have damaged the connector. Some connectors have fuses in them; see if yours does.

    Inside the unit, I'd start looking to see if toroids/transformers have broken loose. Those things can be somewhat heavy for their size, and if they were not held solidly mechanically, the connecting wires would be easily sheared off.
     
  10. ke5nnt

    Thread Starter Active Member

    Mar 1, 2009
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    I consider myself a good person of strong moral character, it's only fair I should pay for it if I get it working and keep it.

    I think I've discovered the problem. I was tracing wires inside the PSU around and found a connector that felt quite loose on the power switch PCB. I took the board out and look what I found:

    [​IMG]

    [​IMG]

    I don't think that the jumper was fully seated when it was soldered on at the factory. The jolt from the drop or shipping must have forced it to seat fully and it broke the copper traces on the PCB. I suspect that's enough to cause the unit to not work :rolleyes:

    Anyways, have a look at the second photo. There is a third jumper location that is unused. It looks like all of the connections are the same, in fact, I'm almost certain that they are. Unless anyone has a reason that I'm just missing, I'm thinking I can just relocate the damaged jumper to the empty position and everything will be good to go. Otherwise, I'd have to try and solder wires from the jumper pins to the traces beyond the break.
     
  11. SgtWookie

    Expert

    Jul 17, 2007
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    If the board has only two layers, you might be in luck.

    If the board has more than top & bottom layers, and the jumpers connected to anything in the middle layers, you're not so lucky.

    It doesn't say much for their QC that this board made it through. In the 1st photo, you can see the pin in the lower left corner didn't flow properly, and at least 3 pins in the 2nd row on the left didn't get soldered properly.

    Those traces are pretty wide; obviously for carrying a fair bit of current without getting too warm.

    I would remove the remainder of the damaged pads from the jumpers, and get some fairly stiff bare solid copper wire (say AWG-16 to AWG-18) and wrap a couple of turns around each post, with a length of the wire (at least 1/2") soldered along the remaining trace. At that rate, you might as well just solder to the next post as well as the trace.

    By the way, solder has more than 5x the resistance that copper does. For that reason, you really want the wire in contact with the pins/posts, and the trace.
     
  12. ke5nnt

    Thread Starter Active Member

    Mar 1, 2009
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    Even better... it's a 1-layer board. I'm just going to move the jumper from the damaged area to the empty jumper slot.
     
  13. ke5nnt

    Thread Starter Active Member

    Mar 1, 2009
    384
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    Ta-Dah!

    [​IMG]

    Everything seems to be in order now. I cleaned up that board, this whole thing isn't exactly skilled soldering, but hey... "made in China"...
     
  14. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    What's the extra set of connectors for? The ones without Earth Grounds in the middle?
     
  15. ke5nnt

    Thread Starter Active Member

    Mar 1, 2009
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    The two connectors with earth grounds are 0-30V 0-3A variable outputs that can be internally tied together for a single 0-60V 0-6A output. The output without earth ground is a fixed 5V 3A output.
     
  16. Wendy

    Moderator

    Mar 24, 2008
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    How much did it set you back again?
     
  17. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    good job, easier than shipping it back
     
  18. ke5nnt

    Thread Starter Active Member

    Mar 1, 2009
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    The repair cost me nothing but a little solder of course. I really did nab this at a steal, they seem to retail for $169.99 plus a hefty shipping charge (~$30), I got this for $90.00, shipping included. Definitely can't complain.
     
  19. SgtWookie

    Expert

    Jul 17, 2007
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    If the two connectors with earth grounds are 0-30V and 0-3A, you won't be able to get more than 3A output if you connect them in series to get 60v.
     
  20. ke5nnt

    Thread Starter Active Member

    Mar 1, 2009
    384
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    Perhaps I should have phrased that better. They can be internally tied together for a single 0-30V 0-6A parallel mode, or 0-60V 0-3A series mode.

    It's a nice unit. I'm a very happy man. Christmas has come early for me this year, lol. Got a new power supply, a PicKit 2 with low pin count demo board, and I suspect Santa is bringing me a new Digital Multimeter.
     
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