Keurig Power Supply Troubleshooting

[wilheldp]

My neighbor likes to give me stuff that has died on him to see if I can fix it.  Yesterday, he handed me a Keurig B60 coffee maker.  I told him that they were pretty complex, and probably wouldn't be able to fix it, but he said that the problem was just that it wouldn't turn on.  That gave me hope that it would be something simple that I'd be able to fix pretty quick. 

I got the thing apart today and I have 2 initial thoughts:

1.  Holy crap this thing is a PITA to take apart.  It took about 20 screws and a bunch of stiff plastic clips to take the housing apart, and I had to cut 3 ground conductors that were pop-riveted to the bottom plate of the housing just to disassemble it.

2.  This thing is needlessly complex.  It seriously looks like a Rube Goldberg machine to make coffee.  No way a coffee maker needs this many moving parts.

Anyway, I finally got access to the noise filter board and power supply/distribution board.  I have continuity from the plug blades all the way through to the output of the power filter board, but when I power it up, I get ~50 mV across line and neutral.  I removed the primary connector from the transformer, so I don't think it is a failed transformer (common Keurig problem) causing the problem.

The noise filter board just has 2 inductors, an X2 capacitor, discharge capacitor, decoupling caps, a diode, and a MOV.  I desoldered the MOV, and got identical readings.  I plugged it in to a Kill-A-Watt, and I'm putting 123 VAC into the board, but it is drawing 0A and 0W.  Any idea what might be causing this issue?

[wilheldp]

Figured it out, but found another problem.  It turned out to just be an open circuit across the primary on the transformer, which is what I thought it was to begin with.  But the reason I didn't figure that out before is because my EEVBlog meter isn't very useful on mains voltage.  It was reading 50 mV across the mains, even when I hooked it directly to the mains.  I re-tested everything with my Agilent meter, and mains was getting where it was supposed to.  I bodged in a 14.5 V transformer I had laying around, and the Keurig fired right up.

[electr_peter]

Have you used "AC" voltage setting on DMM to measure mains? If DC voltage mode was used, you could see only small DC voltage, but not full AC mains.

[wilheldp]

Have you used "AC" voltage setting on DMM to measure mains? If DC voltage mode was used, you could see only small DC voltage, but not full AC mains.

I just figured it out.  I thought that the "V" setting one click clockwise from "off" was the auto-sensing voltage range, but now I see that it is one click counter-clockwise.  I had it set to measure VDC instead of VAC.