HSI Nav receiver problem

[GlennBob]

Help ! !   I bought a used  HSI / NAV  unit from a guy in Florida.  I finally got it hooked up (all the pin-out wires in the right places ), but when I push the Marker Beacon test switch to test the lights, they don't work.  The common wire that goes to all three lights carries the current and the light fixtures are in plastic tubes so they "float" and are not grounded.  When I put a meter to the cases it reads 7 volts and when I push the test switch it drops to zero.  Everything else on the radio seems to work, but I can't make the lights work.  I took the center wire off each light and ran a jumper from ground and then they light up ( but very dimly ).  The bulbs are all fine.  I'm stuck ! !   Any ideas ?   This is a Narco 124 TSO unit.  About 1977 vintage.  I have the manuals but don't know what else to try.

Anybody got any ideas ?   Email me at  EZskyboy@hughes.net

Thanks,

Glennbob

[GlennBob]

Hey guys, . . . I get to answer my own querry ! !  

I called  NARCO AVIONICS and they helped me check all the wiring configuration,  and then we traced the problem to the wrong voltage bulbs! !   Turns out, . . the bulbs were supposed to be only 5 volt bulbs and the ones in my unit were 12 volt.  When I push the "test" button, the resistance (from 3 bulbs) was too great to light all three simultaneously.  So all I have to do is get the right voltage bulbs,  or wire up some L.E.D. bulbs to handle only 5 Volts.  I'm quite surprised because the guy who sold me this unit cautioned me not to use the L.E.D.'s because he said the right bulbs were only supposed to be 5 volts.  Here he ships this thing to me with 12 volt bulbs in it ! !  Go figure ! ! !

Happily resolved,

Glennbob