Newer 12V 5A Power brick no longer putting out full (enough) current - Page 1
Forum section: electronics / repair

author: born2fly2
author_rank: Newbie
timestamp: July 11, 2020, 01:29:25 am
content: I have a 7 month old power brick for my security camera dvr that stopped putting out more than 1.5 amps, suddenly. I've gone through it twice with a MM and everything seems to be as it should. I was not able to test the opto coupler, so I don't know if that could be the problem. The inductors seemed to be within range when I ran an ohms test on them. The 'yellow' guy between inductors I did not test either as I am not sure what it is and what it's function is. Basically - I am trying to determine where the point of failure is and what would cause the current to be reduced/restricted. I'm getting 12V and 1.5A. I decided I would challenge myself on this one and what a challenge it is turning into.

author: Rasz
author_rank: Super Contributor
timestamp: July 11, 2020, 01:39:48 am
content: was it in someplace hot like an attic? the sad boring answer seems to be always output capacitorsdo you have a scope to look at the output voltage? or ESR meter? if not then just quickly solder additional output cap and retest the supply to se if there is any difference

author: born2fly2
author_rank: Newbie
timestamp: July 11, 2020, 01:48:37 am
content: I don't have a scope yet, just a MM and workstation stuff ...it's on my list, but I did remove the electro caps and they all tested good. I checked all of the smd resistors & caps, all good. Really stumped. I know a scope would really help out but holding back pulling out the credit card for the moment, but.... VERY tempted. Thank you for your input.

author: born2fly2
author_rank: Newbie
timestamp: July 11, 2020, 01:54:10 am
content: Interesting info - thank you. They sell for about $15+ online, from what I've seen. YES, for fun and also education, still learning all of the newer tech. Was an ET in the navy 4 decades ago. Will try the safer and cheaper route. Curiosity has me and the fact that it cost me $20 to get another brick (hopefully better quality this time)

author: sleemanj
author_rank: Super Contributor
timestamp: July 11, 2020, 01:58:31 am
content: How you are testing this power brick?Never exclude an error in methodology as a reason for apparent failure.

author: born2fly2
author_rank: Newbie
timestamp: July 11, 2020, 02:26:06 am
content: I need 12V and aprox 2.3 A to run the DVR. What kind 'device' would be required to trick the unit into supplying the 12V?

author: TimNJ
author_rank: Super Contributor
timestamp: July 14, 2020, 01:49:44 am
content: Quote from: blueskull on July 11, 2020, 02:22:12 amIsn't this already public?http://www.chongdiantou.com/wp/archives/46552.htmlOr is there another one? The teardown above shows a nice quality product. Only thing I can fault is the SMD Y-caps, and that's really just a preference. Although they are Y-rated, and supposed to fail safe, big surface mount ceramic caps are a little scary with respect to cracking during manufacture, or further down the line.

author: station240
author_rank: Unknown
timestamp: July 14, 2020, 04:06:20 am
content: Have you pulled the output diode out and tested it ?It's the TO200 device bolted to aluminium, top right in your photo.Usually these have 2 diodes connected to 3 pins, if one of those diodes is dead, then it would cut the output current in half.

author: TimNJ
author_rank: Super Contributor
timestamp: July 14, 2020, 03:05:06 pm
content: Quote from: blueskull on July 14, 2020, 04:28:51 amAh, so each SMD Y-cap is 2 in series. Is this the way all Y-caps are made, or just SMD type?So, will planar ever be useful for a low leakage application? Medical? Bias/cancellation windings in the transformer to reduce interwinding capacitance?