Maker Pro
Maker Pro

power board - don't know what to try

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
8,393
Joined
Nov 28, 2011
Messages
8,393
I find that very hard to believe. Try applying solder to the shiny areas.

If the copper is really gone, yes, you can bypass it easily using wire. Wrap a short piece of wire around the component lead, solder it to the component lead, then solder each end of the wire to the nearest other connection point on the same track. The left hand track doesn't go past the MOSFET connection, so you only need to connect one end of the wire; cut the other end off.
 

sparkmonkey

Feb 24, 2014
13
Joined
Feb 24, 2014
Messages
13
Thanks for your patience, and many helpful responses. Given that I've tested the diodes now and they seem to be ok, and I have replaced the blown resistor, have I now exhausted the checks that are worth doing at this stage? and I should now proceed to order a replacement MOSFET and heat conductive paste. Are there any other parts that are worth getting on the off-chance to save postage?

I think I might treat myself to some fine wire cutters and pliers while I'm at it.
 

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
8,393
Joined
Nov 28, 2011
Messages
8,393
OK, I've reviewed this thread.

So you've lifted one end of each of those diodes and got open circuit with the red probe to the stripe end on the highest range? That's a good sign.

And you've got (or are going to get) a collection of replacement fuses, and at least one spare MOSFET?

I would replace the bridge rectifier just in case. Even if it's not faulty, it will have been stressed, and it's not expensive to replace. The original is a Taiwan Semiconductor TS4B05G. It's not available from uk.rs-online.com but it is available from a company called Spared Parts at http://sparedparts.com/parts/details/samsung_ts4b05g_bridge_rectifier_diode and they are in the UK.

Its specifications are 4A, 600V, 120A surge, package 25 x 15 mm, leads +/~/~/- at 7.5 mm pitch, hole centre ~13.7 mm from seating plane, diameter 3.25 mm.

uk.rs-online.com don't seem to have any drop-in replacements. They have several in a "GBU" package, with flat wide leads, but these have a 0.2" pin pitch instead of a 0.3" pin pitch like the original.

You could use a device in a GBL package, with flexible wire leads that you can bend to fit the holes in the board, such as http://uk.rs-online.com/web/p/bridge-rectifiers/7082696/ (pack of 5 minimum).

Or you could try to find a replacement locally. Or you could just not bother replacing it. It's up to you.

Those seem to be the main likely suspects and I think it's worth trying the board with them replaced.

Another suspect would be the output diode, but if that's faulty, the power supply should just not start up, not go bang. It might "hiccup" (make a regular ticking noise).

The optocoupler is also a possible suspect but these are not easy to check. It's the black plastic device with two pins on each side that straddles the wide white marking near the bottom in the picture in post #1, next to the blue capacitor, left and slightly down from the "C" marker.

You might want to replace it just on suspicion. See if you can find the part number marking on it, and look online for a replacement.

I've confirmed that 6715301 is the right rs-online catalogue number for the MOSFET.

No "heat transfer pad" is needed; the device is in a "full plastic package" which doesn't need any separate insulation. It bolts straight onto the heatsink. Tighten it firmly but not unnecessarily tightly as that could crack the plastic.
 
Top