Helping out (and a free cup of coffee)

My local favorite coffee hang out, Dublin Roasters, had a problem... I thought they had closed when I didn't see their OPEN sign lit.  I stopped in and they were open, and asked about it (along with a cup of Volt Blend and a kitchen sink brownie).  Apparently the yoga class had crushed the plug.  They had replaced it but still wouldn't work.  I offered to take a look at it for them.

There were two problems, the new transformer they had found was the wrong voltage (6V) and way under-powered (like 300mA).  Getting it home, I opened the back and hooked a bench supply to the power contacts.  With a 1A current limit set, I slowly took the voltage from 6V up, the sign turned on at about 10V, at 12V it was going good, and pulling about 600mA for an LED sign.

As luck would have it, I had a leftover power supply with 12VDC and 3.15A laying around which worked perfectly.  I also happened to notice part of the second "e" in coffee was out.  I found that the PCB trace had broken on that small substring of lights, the LEDs were 5-6 in series for the 12V with a 150 Ohm current limiting resistor in the string.  A small scrape of the conformal coating and touch with the soldering iron, and it was back to full "e" status.

Thanks Dublin Roasters for the free cup of coffee and oatmeal bar on return!