737-200 fire unit diagram

[dc8flightdeck]

Im looking for a diagram to see which cannon pins to the fire handles arms the squib (to unlock the handle) and what power is required. I get the impression it uses AC power that goes to an internal DC Rectifier circuit, that probably goes to a DC solenoid that unlocks the squib.

I had no problem finding switch circuits through the cannon connectors when I pull up the fire handles. These are usesful to command engine fuel cuttoff. I also found the pins (1 and 2) for the handle fire lights.

But I cannot get a circuit when I rotate the switch right or left, which is a bummer. Most likely that means the circuitboard inside the unit is part of that  loop so the wires in the fire handle right and left position do not go diret to the cannon connector pins.

Justin

[fsaviator]

I believe pins 14 and 15 are the #1 solenoid, 29, 30 are the #2 solenoid, and 5 and 6 are the APU solenoid.

don't quote me on this but I believe power is 28VDC.

Warren

[dc8flightdeck]

Thanks. On this unit those pins go though the switch that is moved when the handle is pulled verically.

Does an NG Handle also pull up vertically before twisting right or left? I know NG has an exta test function that is not on the -200.

[fsaviator]

My unit isn't an NG, so it should be the same as yours.

[mickc]

Justin, do you have plugs on the bottom of each handle?

Ill dig my -300 wiring diagrams out and send you the relevant sections

[dc8flightdeck]

Thanks!! Yes, its complete with cannon plugs.

[mickc]

I haven't had much to do with -200 aircraft, but this info from the -300 should still be applicable:

This shows the whole fire panel and the handles, with all the pin numbers for both.

[dc8flightdeck]

It appears to me this diagram only works when the connon plugs are connected to the various aircraft systems, meaning that while disconnected from an actual 737 the circuits are in an open state .

Here are the pin connections I plan to use to interface the fire handles to the sim. These are the same in each of the three fire handle cannon plugs.

pins14 and 13, right fire extinguisher (I will use this with a KE-108 keyboard emulator)

pins 7 and 8, left fire extinguisher (I will  use this with a KE-108 keyboard emulator)

pins 27 and 28 are handle release solenoid. This is powered by 26v AC through the DC rectifier located inside the handle unit (4 diodes). I just tested it. I have no idea if it would work on 60hz AC, odds are it could get too hot since its designed for 400hz. I plan to run these on the same 26v AC 400hz power that will go to the the corresponding fire light inside the handle.

Pins 1 and 2 are the 26v for the fire lights. (2 is ground)

[mickc]

Sounds good,

You could also use pins 24 & 25 for the handle up/down position for engine / hydraulic shut-off.

Im just trying to see why you need to use AC power for the handle unlock ?   The whole fire systems uses DC power.

The diodes you described are used for the fault / test circuits.

This attached diagram shows the actual wiring of the handle, and shows the diodes in question.

But of course if it works, then thats all that matters 

[dc8flightdeck]

Yep it works. I do not have 28v dc going to the TQ so I am glad to keep it all AC. 

Justin