Posts: 221
Joined: 2/18/2007 From: Ocilla, GA, USA Status: offline
Power supply is the Mastech hy5020e, it has been working just fine for charging A123 cells and I've also been using it to charge the deep cycle battery. When it died, it was maintaining 13.2v and 0.1 amp to the deep cycle battery. I was not home when it died, but when I did come home it was dead. Now, it won't turn on, no noise, no fan, just nothing, not even a burnt smell, and no output from the terminals either. While I was gone there was some bad weather.
Do any electronic guys out there know what might have happened to it?
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quote:
ORIGINAL: cwharper
Power supply is the Mastech hy5020e, it has been working just fine for charging A123 cells and I've also been using it to charge the deep cycle battery. When it died, it was maintaining 13.2v and 0.1 amp to the deep cycle battery. I was not home when it died, but when I did come home it was dead. Now, it won't turn on, no noise, no fan, just nothing, not even a burnt smell, and no output from the terminals either. While I was gone there was some bad weather.
Do any electronic guys out there know what might have happened to it?
Sounds to me like you might have blown a fuse.. Pop it apart and have a look inside and see if you can spot a fuse inside it. Just try not to touch anything.. depending on how long ist been sitting things like that can hold voltage for a while andf you might kill yourself if you go fingering around in it. If its a fuse you should just be able to pop it out and pop a new one in no problem.
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Joined: 2/18/2007 From: Ocilla, GA, USA Status: offline
I have opened it up and had a good look around already. I don't see any sign of a fuse. Yes I am aware of the lethal voltage present in a power supply plugged in or not. With the supply plugged in and using a fluke multimeter I have identified where the AC is initially fed to the board. Then, with the on/off switch to on, there is 340v dc present across what looks like a capacitor on a modular circuit plugged into the main board containing a small transformer. On this same board, at different terminals there is regular 120v ac present. I'm guessing the transformer is stepping up the voltage and then a diode is converting it to dc with the capacitor filtering out the ripples. From this a wire of about 16 to 18ga is leading to what looks like a mosfet and the other two connectors of the mosfet (about the size of a dime) have 12ga wire leading back to the main board. These two wire have nothing across them, but they each have 340v dc back to the wire from transformer. The 340v disappears with the on/off switch turned off.
What I was hoping to find is a single burned out component to replace, but testing components installed in a circuit is just about impossible with collateral flows around the components.
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I really appreciate your willingness to help. Pictures are not a problem, and I can take more if needed. Here are some pics of the innards.
First pic, front of unit Second pic, left side of unit where 120v ac comes in, univeral plug on bottom and voltage selector on top (it is on 115v), mains goes to switch on front of unit then to back again where it connects to main board (see last pic). When switch is on this is hot with 120v ac Third pic, on/off switch to far right bottom, the standing up board is modular and can be removed, the thing with only red and black wires, is attached to the removeable circuit and reads 0.1 ohms with it disconnected from the circuit. This modular board has one IC chip which I cannot identify, it has 4 legs. Fourth pic, different angle of pic2 Fifth pic, top view, front of unit to right and back to left. Sixth pic, right side of unit, the two other standing up circuits are removeable as well, and they contain IC chips (14 legs) which I cannot identify. Last pic, bottom of unit, on/off switch to top, right, ac mains to top, left.
< Message edited by cwharper -- 9/3/2007 6:13:25 PM >
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Man thats a nice looking power supply... I didnt see anything that looked like a switch either. What about under any of the boards?? I have not ever seen a device like a power supply that didnt have some sort of a fuse for protection. I have an old pc power supply I converted to run my battery chargers and it has a fuse in it.
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"And I looked, and behold a pale horse: and his name that sat on him was death, and hell followed with him"
Unfortunately, trouble shooting a PSU without a schematic is almost impossible. Starting points are searching for any discoloration (dark spots due to heat) on the circuit boards and on all the components. Even if you can find a burned component, it's failure can be due to another less obvious failed component farther up the circuit path.
Occasionally, you can have a cold solder joint open up. While this may seem bazaar, place the PSU in the fridge for an hour to cool it down and see if it restarts. The downside to this is condensation -- you will need to keep it under a good airflow until it returns to room temp. If it does restart, then it may be a bad joint. I'm not optimistic that this is the case since it has functioned for some time at operating temperature.
I have replaced a number of fuses in PSU's, but in the vast majority of cases, the fuse has blown almost immediately due to an internal short. These were computer PSU's and were simply tossed rather than spend time searching for the problem.
Since yours is a rather expensive PSU, your best bet is to have it serviced by a qualified technician.Tanic Packs carries this power supply -- you might contact them about service or locating a service center. Warranty is listed for a year.
Generally in products of this type, repair involves complete board replacement rather than component troubleshooting -- it's usually cheaper in the long run.
< Message edited by Andrew -- 9/3/2007 9:16:40 PM >
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Crawl n clod, Correction, it "was" a nice power supply, now it's a door stop. I've converted a couple of atx ps to run chargers and saw the fuses in there also, the only place I haven't looked yet is behind the lcd display because it looks the toughest to get to.
Andrew, I'll try the fridge test. And I was afraid that modular replacement is the method of choice for repair.
After I've thought about it some more two possible causes that could have occured are backfeed from the battery if the utility power blinked or went out while I was gone and/or a lightening surge damaged something.
I've already ordered another ps identical to this one, and will install a 25 amp 50v diode on the positive leg to the battery to make darn sure feedback doesn't occur again and just compensate for the voltage loss with the ps. Seeing just how sensitive it is, I will power the whole thing through an UPS with surge suppression and battery backup.
Does this added level of protection seem adequate or is there something else I can do to protect it?
And then after the warranty runs out I might open the working one up, measure voltages, and compare with the old one.
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When you see the mushroom cloud, you will know then that I have finally achieved fusion.
It probably as a varistor that cuts off power when it exceeds X amount of current near the input. The problem could be as simple as a 10 cent transistor that has failed in the voltage regulator circuit.
If you can get a circuit diagram, a local ham or t.v. repairman can probably fix it for much of nothing.
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Joined: 8/14/2007 From: Ventura, AB, USA Status: offline
The fuse is located in the housing that accepts the AC power cord. Look at it carefully - you can pop it open to reveal a fuse from the outside of the unit.
Dave
< Message edited by Probedude -- 9/4/2007 4:25:44 AM >
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Joined: 8/14/2007 From: Ventura, AB, USA Status: offline
That bank of electrolytics right after the 3A diodes should be at a pretty high voltage when plugged into the mains. See if you're getting voltage there.
Is there a PWM IC driving the primary mosfet? If so, what's the pn?
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killed my power supply, any ideas on how to fix? - 
