12V to ±32V 180W SMPS

WSJ · 11th May 2011, 10:58 PM

I bough two 180W, 12V to ±32V Power Supply Boards listed on eBay. One for $29 with shipping.
One powered up OK with no load, but the other one smoked as soon as I applied 12 V to the input terminals. The 12 V power supply was set to 2 amps current limit and the input voltage dropped to 4 V. The TL494 was very hot, so I need to get it out and check the drivers and FET’s. I charged the output caps to check for shorts, 3,300uF @ 35 V. I could send it back to Hong Kong for $10 postage, but that wouldn’t be any fun.

180W DC12V to DC±32V Boost Power Supply Board Kit 1PC | eBay

theAnonymous1 · 11th May 2011, 11:16 PM

I have one of those too. The output isn't regulated and it's closer to +/-36V when in a running vehicle.

Sorry, no clue where to start to help you out.

ppia600 · 12th May 2011, 12:25 AM

Did you have the transistors sinked, could they have overheated quickly or maybe they were just bad already. Either way, there aren't many parts to replace if you have to. :lol: Amazing what you can buy on fleabay.

WSJ · 12:34 AM

Quote:

Originally Posted by ppia600

Did you have the transistors sinked, could they have overheated quickly or maybe they were just bad already. Either way, there aren't many parts to replace if you have to. :lol: Amazing what you can buy on fleabay.

No load and no heat sink, the first one worked fine and nothing got hot.
I pulled the TL494 and the 12 V current is now 6 mA. I pulled primary windings and replaced them with 12 V lights. I will bias each FET pair on one at a time. I have an old board with a TL494, but no new ones.

Perry Babin · 12th May 2011, 01:17 AM

Confirm that you have ~5v DC on the gate pads of the FETs. Also confirm that the gate resistors are within tolerance.

WSJ · 12th May 2011, 01:30 AM

Quote:

Originally Posted by Perry Babin

Confirm that you have ~5v DC on the gate pads of the FETs. Also confirm that the gate resistors are within tolerance.

I pulled 2 FET's and 1 PNP on one side, all three are bad. The other side witches the lamp OK without the TL494 installed. I will get a socket installed and a TL494.

theAnonymous1 · 12th May 2011, 01:41 AM

You can rule out overheating as the culprit. I've had mine running a small load 24 hours a day for over 6 months now without a heatsink. I'm only pulling a few watts from it, but the FETs aren't even warm.

luka · 12th May 2011, 06:48 AM

always with this kinda kits, measure if there is short on the input right out of the box, check if everything is soldered on ok and if nothing has broken off... current limited supply is always good

WSJ · 06:28 PM

I received the parts to repair board #2, with new FET’s, TL494, PNP driver and diode it’s working. When I applied a load to board #1, I found it also had a problem, see pic for CE short of the PNP driver. This means neither board was tested at the factory with a load.

luka · 13th May 2011, 07:14 PM

low cost = low testing, which would mean that you should be happy it even powered up once

12th May 2011, 12:25 AM	#3
ppia600 diyAudio Member Join Date: Jun 2007 Location: Louis y ana	Did you have the transistors sinked, could they have overheated quickly or maybe they were just bad already. Either way, there aren't many parts to replace if you have to. :lol: Amazing what you can buy on fleabay. __________________ Don't worry... you can always turn the gain down!

12th May 2011, 01:17 AM	#5
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Confirm that you have ~5v DC on the gate pads of the FETs. Also confirm that the gate resistors are within tolerance. __________________ Links >> Basic Car Audio Amp Repair * Basic Car Audio Electronics * New Site * Basic Switching Power Supply Design * Basic Computer Skills << Links

12th May 2011, 01:41 AM	#7
theAnonymous1 diyAudio Member Join Date: Feb 2004 Location: Anonymityville	You can rule out overheating as the culprit. I've had mine running a small load 24 hours a day for over 6 months now without a heatsink. I'm only pulling a few watts from it, but the FETs aren't even warm. __________________ "If you don't like funerals don't kick sand in Ninja's face." - Ninja

12th May 2011, 06:48 AM	#8
luka diyAudio Member Join Date: Sep 2005 Location: in Slovenia :)	always with this kinda kits, measure if there is short on the input right out of the box, check if everything is soldered on ok and if nothing has broken off... current limited supply is always good __________________ home page @ http://www.classdaudio.tk/ @ 24/7 all year long I FEEL SLOVENIA

13th May 2011, 06:25 PM	#9
WSJ diyAudio Member Join Date: May 2009 Location: GILROY, CA	I received the parts to repair board #2, with new FET’s, TL494, PNP driver and diode it’s working. When I applied a load to board #1, I found it also had a problem, see pic for CE short of the PNP driver. This means neither board was tested at the factory with a load. Last edited by WSJ; 13th May 2011 at 06:28 PM.


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11th May 2011, 10:58 PM	#1
WSJ diyAudio Member Join Date: May 2009 Location: GILROY, CA	12V to ±32V 180W SMPS I bough two 180W, 12V to ±32V Power Supply Boards listed on eBay. One for $29 with shipping. One powered up OK with no load, but the other one smoked as soon as I applied 12 V to the input terminals. The 12 V power supply was set to 2 amps current limit and the input voltage dropped to 4 V. The TL494 was very hot, so I need to get it out and check the drivers and FET’s. I charged the output caps to check for shorts, 3,300uF @ 35 V. I could send it back to Hong Kong for $10 postage, but that wouldn’t be any fun. 180W DC12V to DC±32V Boost Power Supply Board Kit 1PC \| eBay

11th May 2011, 11:16 PM	#2
theAnonymous1 diyAudio Member Join Date: Feb 2004 Location: Anonymityville	I have one of those too. The output isn't regulated and it's closer to +/-36V when in a running vehicle. Sorry, no clue where to start to help you out. __________________ "If you don't like funerals don't kick sand in Ninja's face." - Ninja

13th May 2011, 07:14 PM	#10
luka diyAudio Member Join Date: Sep 2005 Location: in Slovenia :)	low cost = low testing, which would mean that you should be happy it even powered up once __________________ home page @ http://www.classdaudio.tk/ @ 24/7 all year long I FEEL SLOVENIA

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