Thursday, 29 December 2016

Clansman 24V Power Supply - Major Setback!

The project to build a self contained 'battery eliminator' for the Clansman using a 24V 3A SMPSU has suffered a major setback today. Rigged up for its first live test, I switched on the mains supply - there was a blue flash and everything in the workshop went dark.

The supply had tripped the mains, right back to the main breaker in the house. On inspection, one of the mains fuses in the IEC socket was very much blown - it had literally exploded!

Checks for shorts etc done again, the fuse replaced, and this time the mains coming via the isolation transformer and a portable RCD, I tested it again. There was a brief flicker but then the RCD reset successfully - due to both fuses in the IEC socket having blown!

Inspection of the SMPSU module revealed it to have failed catastrophically.

In the top photo, and more clearly in the bottom one, there is a 'defect' visible in the solder. The two traces this defect was over are the DC output. It looked like a piece of loose wire had got soldered over the tracks (the actual bridging part of the wire had been blown off by the fault current!).

I later unsoldered this piece of wire, and found that it is actually the entire leg of one of the capacitors, nicked but not cut off, and bent right over the board by the forming machine and then soldered down by the wave soldering process.

This module was bought on ebay from a seller using the trading name 'Yall-UK'. I have contacted them. It is very clear that there is absolutely NO WAY this module could have passed any testing before being shipped. Lets see if they are willing to replace it.

No comments: