Ice Tube boost converter only supplying 9.5V

[adafruit]

well, we're not sure whats going on but we could try sending you new boost parts - inductor, 100V 22uF capacitor, FET, MBR160 diode and see if that helps? email support@adafruit
otherwise it must be either a measurement problem or a soldering issue

[crazybutable]

I did more resistance checks with the meter to make sure that everything was soldered in the right spot and one of the legs of the fet is not connected to ground. This is very odd because visually it looks like a perfect solder joint. I'll continue investigating and report back.

[crazybutable]

Sorry, I was in a hurry when I wrote that. Let me be a little more clear.

When I checked with a ohmmeter, there was no connection between the source of the jfet and Gnd. Not good. I've checked, and double checked, and soldered this joint twice and there still was no connection to ground. So I popped the inductor back in there, and ran a green wire from the source pin to ground and... it worked! 52 volts.

For completeness, I disconnected the green wire from ground (not from the jfet) just to make sure soldering the green wire didn't fix the bad connection somehow and, sure enough, the output voltage went back down to 8.8 volts.

So I suspect a bad board.

Normally I'm all about the green wire fix but in this particular kit, with this particular fix, I'm not so sure about the safety. I mean, it looks fine to me, it's just ground, but I'm no expert. Please advise.

[adafruit]

it could be that some of the copper was scraped away during soldering...theres plenty of local grounds so just solder a short wire and you should be good to go

[aheliason]

I, too, am at an impasse at the point in construction where I should be seeing boost voltage. I am only seeing the ~9v at the boost capacitor. After reading these forum entries I have re-checked the ground and all continuity as well as the diodes front to back. All seems to be in order. I do see that the waveform at the gate of MOSFET Q2 is only 1.9 volts peak. There is no sign of switching at the drain pin. Next, I removed Q2 and found that at pin 12 of the microprocessor IC2 it is still less than half of Vcc. Is this normal? At first, I thought the FET had failed but now I am not so sure. Any suggestions would be appreciated.

[adafruit_support_bill]

I removed Q2 and found that at pin 12 of the microprocessor IC2 it is still less than half of Vcc.

And Vcc is measuring 5v? That shouldn't be.

Carefully remove the processor and measure the resistance between pin 12 & ground. (there should be no conductivity at all).

[aheliason]

Thank you! All is well again. At pin 12 the resistance to gnd was 22 ohms! I had mis-read R5 and it didn't appear on the theory diagrams. A bit embarrassing, but when I made it 10K as it it should have been, and put the FET and IC back in, the boost measured 55 volts. Now I can continue. I really appreciate your immediate assistance, thanks again.

[aheliason]

My unit is built and is working great but now I want to make some mods. As yet I have not found an Ice Tube schematic in a format I can view. Please help again.

[adafruit_support_bill]

You can download EagleCAD for free and view these files: http://www.ladyada.net/make/icetube/download.html

The Design page also has the individual sections of the schematic broken out with explanations: http://www.ladyada.net/make/icetube/design.html