I decided to test how my FAB1248 DC/DC Converter will behave in a short circuit condition. It is unavaoidable to experience short circuit when you’re playing around with electronics. Sooner or later, you’ll experience it. The question is will the FAB Modules survive if there was ever an accidental short-circuit?

Will our FAB1248 Module release the magic smoke?  Will you need to buy another FAB Module from me to replace your short-circuited DC/DC Converter?

Here are the results of my testing:

TEST PROCEDURE:
We connected our FAB1215 Power Supply Module, with a FAB1248 plugin to a 12Volts DC Adapter (wall wart). We then attached a multimeter to monitor the voltage lines across GND and +48V output.

Voltage level (without load, open circuit) = 47.88Volts

Next, we connected the 48Volt line directly to Ground, thus creating a short-circuit condition. A big spark occurred. We let the 48Volt line connect to Ground for several seconds. Measured output voltage during this short circuit condition is 34.8mV according to the multimeter.

Next, we removed the short-circuit condition.  Measured output voltage went up to 1.25Volts, but not our original 47.8Volts…. Hmmmm….. at this point, I’m wondering if the FAB1248 survived… It doesn’t seem to be looking good. It’s only hovering around 1.25Volts.

Removed the 12Volts input voltage  from the FAB Module. Now, the measured output voltage is now 0 volts, naturally… since there is no voltage  input source.

Hooked up the 12Volts input again to the FAB Module…. Voila!  We measure 47.88Volts again, and our FAB1248 module is still working properly. I repeated this test procedure several times and each time, the FAB1248 comes back to life after doing a “reset” …. just unplug the 12Volt source, and plug it again.

So I’m happy to report, that yes, the FAB1248 will survive a short-circuit condition and not break down.  You may need to “reset” the converter by powering off, then powering back on…. of course, after you’ve removed the short-circuit condition.

I made some tests using the final component values for our FAB1248 DC/DC converter.

Using a 12Volts DC input, phantom power voltage output remained constant at 47.90Volts, up to 47.84Volts at various loads and current draw.

For example, at 57mA current load, voltage output measured is 47.87Volts, with 152mV ripple according to our oscilloscope. This translates to about 0.31% ripple!  Ripple frequency has a period of 6.07us, or 164.7khz.

Continue Reading…

Here are some photos showing the FAB1215 Power Supply Module powering some FAB modules via a ribbon cable.

Continue Reading…

Here’s a photo of our FAB1215 Power Supply Module, outfitted with our DC-1248 (+48V converter module).

I finally got the chance to test the 48V power supply by hooking up our FAB2010 XLR Input Module, FAB2110 Input Transformer Module, and FAB3010 XLR Output Module, using them as a pass-through before going into an API 512C preamp.   But instead of turning on Phantom Power on the API preamp, I used the 48V source on our FAB module.

Continue Reading…

Yesterday, we got the boards back from the PCB fab house. Today, I built the FAB1215 prototype and tested it.  Now, we have a power supply to power all our FAB modules. Yay!

This convenient power supply is powered by a simple 12VDC power adapter (wall wart). The one I’m using is rated 400mA and it’s the only one I can scrounge around… but I’d recommend a 1Amp power adapter so you have plenty of power to spare.

The +/-15Volts is generated by an off-the-shelf part, and the +48Volts for phantom power is generated by our DC-1248 Module (12VDC to 48VDC converter).

The FAB1215 has (1) DC jack to accept the 12Volts input, and (2) IDC headers that route +/-15Volts, and +48Volts so you can power (2) channels of your project.  The +/-15V is rated up to 190mA, and the 48Volts is rated up to 60mA  (this 60mA figure may change once I finalized on the component values and complete testing).  You simply hookup power using 10-pin ribbon cables to your FABs. It’s that easy.

Continue Reading…