IBBS input to GTR 255A?

Hi,

I have a G3X Touch install with a TCW IBBS 6A backup battery supplying both screens, the GSU25 and the GEA24.

I was wondering that instead of supplying a backup power supply to the 2nd screen could I use that supply for the GTR 255A radio? However, on looking through the interconnect drawings and manuals it doesn't show that option.

So my question is can I supply the radio from a 6A IBBS and if so would that be through one of the pins 30/43/44?

Thanks in anticipation

Nick
G-RVWJ
Preston UK

I use this setup to power my GTR200 com (none of the com radios have dual power inputs) so it will run off battery back up or main bus. I used a 30a schottky diode to do the job. If you need the PN send me an email and I will find it. I'm not sure the IBBS unit can actually handle the transmit current for very long so check the specs.

Hi Nick

The GNC255A doesn't have dual isolated power input circuits (like the GEA24, GSU25 and G3X have). This leaves you with the following options:

1. Power the GNC255A only from the IBBS
2. Power it only from the ship's main power
3. Use a diode to create the isolation yourself

Assuming you want to run the GNC255A from the main supply most of the time but switch automatically to the IBBS at other times, you'll need option 3. The diode you need is e.g. this from B&C.

If you don't fit a diode, the IBBS will be powering everything on the main bus (or avionics bus if you have one), which will be too much for it. The diode prevents the power reaching the other components on the main bus. The G3X/GSU25/GEA24 have diodes internally, which is why they don't need an external one.

The B&C diode actually contains 4 diodes and you connect it such that the power can flow to the GNC255A from either the main bus or the IBBS but not back the other way.

Walt/Riaz,

Thanks for the replies and the diode makes total sense. I may leave it as it is and revisit later.

cheers

Nick

You could just use the pass through power option, which will use ship power when available and power through the IBBS when the switch is on and the ship power is lost.