RE: killed my power supply, any ideas on how to fix? (Full Version)

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cwharper -> RE: killed my power supply, any ideas on how to fix? (1/3/2008 12:30:07 AM)

Jrb1, I'm don't have much of a background in electronics. While I understand what individual components of a circuit do, it's hard for me to grasp what they do when put together. The reason I started this thread was I hoped someone would have that little light come on in their head to immediately know the trouble.

I searched for inrush current limiters (Thermisters) on digikey and discovered that your link is to a manufacturer of them which digikey carries and probably other parts houses as well. I understand how the thermister works and it sounds like our solution to tripping the inverter but the problem for me would be to choose the correct size. The formulas on your link mention precharge voltages of 480 VAC. These are internal voltages within the power supply. I have indeed identified these same voltages on one of the modular components within the mastech, but I am not going to start monkeying around inside the mastech adding stuff here and there. I don't at all advise probing around inside the mastech as there are lethal voltages in there that could kill you.

So then the question is would adding a thermister in series to the standard household AC cord work? I don't really see why not, but choosing the correct size or quantity would be my problem.

Having said that, I am not having any problem at all getting my Mastech to turn on using the Xantrex 1000 watt TRUE sine wave inverter. There have been instances where I had a loose connection to the battery and the inverter gave a low voltage error but I just turned everything off, jiggled the cables and restarted. Were you using the Xantrex TRUE sine wave inverter because I think they also make the cheaper square modified sine wave version?



jrb1 -> RE: killed my power supply, any ideas on how to fix? (1/11/2008 1:02:54 AM)

Have another set of Limiters on the way; the 1st set didn't do much -- exchanged e-mails with mfg.

Also, have gotten my Vector 2000W Inverter (w/mod sine) and the 5020 now starts.

Is there any chance CW that you could e-mail me a copy of the schematic?

TIA!

jim DOT blanner AT catpumps DOT com



cwharper -> RE: killed my power supply, any ideas on how to fix? (4/5/2008 9:55:20 PM)

Update:

My Mastech HY5020E doorstop is fixed and regulates like a new one now (no longer a doorstop, will have to find something else for this purpose).

John Mardock (john4648) contacted me from this thread and through me was able to pinpoint the problem by checking for voltage at various points. The symptoms were a totally dead supply with no display and no obvious blown fuses. So he started at the control board. This is a modular board located near the on/off switch. (see picture) The motherboard supplies this modular board with 340v dc, so be careful as it will kill you. With the dead supply turned on, it was getting 340v dc to the board. Next to check for output voltage, the lower three pins of the molex connector should have +/- 5v with the bottom pin as common. (see picture) My dead supply had nothing here and this is where the display gets its power so with no voltage then no display, aaaahaa. He then suspected the pulse width controller (TOP223) had gone bad since there was no ouput from the control board. So I mailed him this modular board, he confirmed the bad part, replaced it, and mailed it back. After I put the board back in, the supply turned on the first time. I checked output voltage at the terminals and tried various loads and it regulates just fine.

The part cost a little over $3 and with priority mail postage turn around time was six days. Can't beat that with a stick.

This of course is only a solution to the specific problem of my power supply, which we now believe to have been caused by a power surge. However, he said one of his mastech's burned up when he connected a 7s pack when it was set for a 4s pack and caused a lot more damage than just the pulse width controller. (reverse current?) But he was still able to repair it.

He also said that if anyone else wanted help in repairing their mastech to send an e-mail, but warned if the problem was any of the transformers inside it could be nearly impossible to fix since they are unique to this power supply and getting a replacement from the manufacturer isn't easy.

I've learned a bunch from this.




petri -> RE: killed my power supply, any ideas on how to fix? (4/11/2008 11:12:22 PM)

Firstoff..... Congrats on converting your doorstop back into a power supply! I'm a fellow owner of a doorstop. Any chance you could share your repair notes, ie places to check for voltages? My PS turns on and shoots right up to 99 volts. It will charge a 4s pack at about 16 amps still but has not voltage or amperage control via the knobs. The LED's showing CC or CV control switch back and forth like the normally would when turning one or the other, so the front panel seems to be working ok. I'm guessing something in the feedback circuit has died? I pulled the PC817 optocoupler and it tests ok on the emitter side using a multimeter with diodoe check, flows about 1V with leads in one direction and open in the other, but the other side doesn't test out on ohms or using the diode test in either direction. Could be the problem? Any notes or ideas you could share would be greatly appreciated! Thanks, Rob D. (Member of the $250 doorstop club)



YeagerThecat -> RE: killed my power supply, any ideas on how to fix? (7/18/2008 1:58:04 PM)

I have a very similar issue - 84 volts, no control of volts or amps. Any one who had fixed this sort of problem, very happy to hear about how you did it. No obvious failure spots in the PS itself (no big surprise).

Thanks

YtC



cwharper -> RE: killed my power supply, any ideas on how to fix? (7/18/2008 7:35:36 PM)


quote:

ORIGINAL: YeagerThecat

I have a very similar issue - 84 volts, no control of volts or amps. Any one who had fixed this sort of problem, very happy to hear about how you did it. No obvious failure spots in the PS itself (no big surprise).

Thanks

YtC


I've never had this problem but I can relay what I've heard others say they replaced to fix your kind of problem. I've even included some pictures of mine I took while trying to figure my problem out. Since you have a working display I doubt your problem is the same as mine simply because the TOP223 must function to give the display +/-5v There are a few other spots to check though. There is a diode across the output terminals and it will take some disassembly to get to it. To check it reliably it must be out of the circuit. If this is bad replace it then see if it fixed the problem. The next area is a dual rectifier diode on the right heatsink in a TO-220 case, looks just like a mosfet but isn't. Some have reported one side of this gets shorted, take it out of circuit to test it and if bad replace it. Further on down this heatsink I think is a voltage regulator that needs to be checked. Something you can check at the same time are the gate resistors for the fets. There are four one for each fet. These you can check while they are still in the circuit, can't remember if they are 15 or 17 ohms, but they should all be the same, if one is bad replace it and try the supply. Next thing to check is the mosfets themselves and they will have to be out of circuit for testing. After that I don't know what else to check. Another tricky thing to keep in mind is that diodes can test good with a meter but fail when under any load. So if you're going to place an order then I would order up all these parts so you'll have them, not that expensive.



YeagerThecat -> RE: killed my power supply, any ideas on how to fix? (7/19/2008 5:54:24 PM)

I have written to the vendor and he is checking back with the manufacturer (very positive attitude BTW)...

but if nothing comes of it, what you have just posted is absolutely fantastic. Digikey here I come. Thanks for taking the time and I'll let you know how I get on.

While it is hardly a work of art, if these are the typical parts that fail, keeping these guys running (I am spinning BLDC motors with it) is a small price to pay for the great facility it provides.

Cheers,

YtC



flybee -> RE: killed my power supply, any ideas on how to fix? (11/14/2008 9:46:19 PM)

I had the same problem with my HY5020E exibiting a constant voltage output of 85 volts without any ability to control the output voltage from the front panel.

I sent an email to Sean at Acifica and he immediately responded with some helpful advice. In essence, he believed that one of the fets that resides on the rear left hand side of the head sink array was bad. In the case of my supply it was a FET that was in a smaller package than the others. The device that was utilized was a 70 Volt, 70 amp device.

He recommended that I replace it with a 200 V rated device. I purchased a 200 Volt 50 amp replacement from Digikey for about 6 dollars, replaced the old device and I'm back up and running like it was new.

Sean's support was outstanding.






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