B737-200 Question?

[magnet]

Are there any radio men out there who can help me with a snag I have? I've got a 737-200 just off a C check and the G/S flags won't clear from the F/os Adi, HSI. The G/S indication seems to work behind the flags but they wont move. When I TXFR to 'both on 1', they dont clear, when I go to 'both on 2' the flags dont stick on thew captain' instruments. I've rang it all out, swapped steering computers, nav rxvrs, txr relays but nothing changes. Can anyone suggest anything to try or can anyone explain what the operation of the flags should be. I know with a VOR tuned they should be out of view, with an inactive ILS tuned they should be in view. I'm back in again in the morning so any clues please?

[freddie the fish]

not too sure about 737 avionics as I've never worked on one - apart from to install floor strip lighting once.
The flag circuits on most a/c I've worked on are parallelled off, so maybe you have an instrument problem. Do you have any spares or a handy a/c to borrow parts from? If you have an ADI or HSI, it might be worth slaving them into each of the four positions in turn to see if the snag clears. I did the same with a 146 a whils ago for a similar defect and it was the ADI keeping the flags in view, while the deviation pointers were still working away merrily behind the flags. Just a thought.

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NO FAULT FOUND

[LME (GOD)]

Try swapping the Nav control panels,
If the NAV receivers are Kings sometimes they don't have the oomph to clear the falgs on a self test, try a different brand, they're all interchangable, have a look at the relevant connectors at the back of the rack, even though they conn out ok you might have a bent or pushed pin making a bad contact, if all that fails go sick....
Good luck

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It flew in, it'll fly out

[Flap shot]

The G/S superflag is 28vdc from the nav rxvr,When you tune in a VOR a discriminant circuit switches this voltage in to lift the flags out. Follow the circuit from the nav rxvr and see if you have 28v into and out of the txfr relay, check for 28v before and after each disconnect on the racks and right up to both instruments, it sounds to me that you have a short circuit to earth which is dragging down the voltage, so out with the old megger. Hope this helps.